Direct on Line Starter (DOL)

Direct on Line Starter (DOL)

A direct on line (DOL) motor starter is an electrical/electronic circuit composed of electro-mechanical and electronic devices which are employed to start and stop an electric motor. Regardless of the motor type (AC or DC), the types of starters differ depending on the method of starting the motor. A DOL starter connects the motor terminals directly to the power supply. Hence, the direct on line motor is subjected to the full voltage of the power supply. Consequently, high starting current flows through the motor. This type of starting is suitable for small motors below 5 hp (3.75 kW). Reduced-voltage starters are employed with motors ab

A direct on line starter, often abbreviated DOL starter, is a widely-used starting method of electric motors. The term is used in electrical engineering and associated with electric motors. There are many types of motor starters, the simplest of which is the DOL starter. Most motors are reversible or, in other words, they can be run clockwise and anti-clockwise. A reversing starter is an electrical or electronic circuit that reverses the speed of a motor automatically. Logically, the circuit is composed of two DOL circuits; one for clockwise operation and the other for anti-clockwise operation. A very well-known motor starter is the DOL Starter of a 3-Phase Squirrel-Cage Motor. This starter is sometimes used to start water pumps, compressors, fans and conveyor belts. With a 400V, 50 Hz, 3-phase supply, the power circuit connects the motor to 400V. Consequently, the starting current may reach 3-8 times the normal current. The control circuit is typically run at 24V with the aid of a 400V/24V transformer. An animation of the circuits of this starter is shown here.

Induction motor

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Three-phase induction motors

Animation of a squirrel-cage AC motor

An induction motor (or asynchronous motor or squirrel-cage motor) is a type of alternating current motor where power is supplied to the rotor by means of electromagnetic induction.

An electric motor converts electrical power to mechanical power in its rotor (rotating part). There are several ways to supply power to the rotor. In a DC motor this power is supplied to the armature directly from a DC source, while in an induction motor this power is induced in the rotating device. An induction motor is sometimes called a rotating transformer because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side. Unlike the normal transformer which changes the current by using time varying flux, induction motor uses rotating magnetic field to transform the voltage. The primary side's currents evokes a magnetic field which interacts with the secondary side's emf to produce a resultant torque, henceforth serving the purpose of producing mechanical energy. Induction motors are widely used, especially polyphase induction motors, which are frequently used in industrial drives.

Induction motors are now the preferred choice for industrial motors due to their rugged construction, absence of brushes (which are required in most DC motors) and — thanks to modern power electronics — the ability to control the speed of the motor.

Contents [hide] 1 History 2 Principle of operation and comparison to synchronous motors 2.1 AC Induction Motor 2.2 Synchronous Motor 3 Construction 4 Speed control 5 Starting of induction motors 5.1 Three Phase 5.1.1 Direct-on-line starting 5.1.2 Star-delta starters 5.1.3 Variable-frequency drives 5.1.4 Resistance starters 5.1.5 Autotransformer starters 5.1.6 Series Reactor starters 5.2 Single Phase 6 External links

History

The induction motor was first realized by Galileo Ferraris in 1885 in Italy. In 1888, Ferraris published his research in a paper to the Royal Academy of Sciences in Turin (later, in the same year, Tesla gained U.S. Patent 381,968) where he exposed the theoretical foundations for understanding the way the motor operates. The induction motor with a cage was invented by Mikhail Dolivo-Dobrovolsky about a year later. Technological development in the field has improved to where a 100 hp (74.6 kW) motor from 1976 takes the same volume as a 7.5 hp (5.5 kW) motor did in 1897. Currently, the most common induction motor is the cage rotor motor

Principle of operation and comparison to synchronous motors

A 3-phase power supply provides a rotating magnetic field in an induction motor.

The basic difference between an induction motor and a synchronous AC motor is that in the latter a current is supplied into the rotor (usually a DC current) which in turn creates a (circular uniform) magnetic field around the rotor. The rotating magnetic field of the stator will impose an electromagnetic torque on the still magnetic field of the rotor causing it to move (about a shaft) and rotation of the rotor is produced. It is called synchronous because at steady state the speed of the rotor is the same as the speed of the rotating magnetic field in the stator.

By way of contrast, the induction motor does not have any direct supply onto the rotor; instead, a secondary current is induced in the rotor. To achieve this, stator windings are arranged around the rotor so that when energised with a polyphase supply they create a rotating magnetic field pattern which sweeps past the rotor. This changing magnetic field pattern induces current in the rotor conductors. These currents interact with the rotating magnetic field created by the stator and in effect causes a rotational motion on the rotor.

However, for these currents to be induced, the speed of the physical rotor must be less than the speed of the rotating magnetic field in the stator, or else the magnetic field will not be moving relative to the rotor conductors and no currents will be induced. If by some chance this happens, the rotor typically slows slightly until a current is re-induced and then the rotor continues as before. This difference between the speed of the rotor and speed of the rotating magnetic field in the stator is called slip. It is unitless and is the ratio between the relative speed of the magnetic field as seen by the rotor (the slip speed) to the speed of the rotating stator field. Due to this an induction motor is sometimes referred to as an asynchronous machine.

AC Induction Motor

where

n = Revolutions per minute (rpm)

f = AC power frequency (hertz)

p = Number of poles per phase (an even number)

Slip is calculated using:

where s is the slip.

The rotor speed is:

 Synchronous Motor

A synchronous motor always runs at synchronous speed with 0% slip. The speed of a synchronous motor is determined by the following formula:

where as p= no. of magnetic poles

For example a 6 pole motor operating on 60Hz power would have speed:

where v is the speed of the rotor (in rpm), f is the frequency of the AC supply (in Hz) and p is the number of magnetic poles.

Note on the use of p: Some texts refer to number of pole pairs per phase instead of number of poles per phase. For example a 6 pole motor, operating on 60Hz power, would have 3 pole pairs. The equation of synchronous speed then becomes: P=3 ,P = no. of magnetic pole pairs.

Right

Construction

The stator consists of wound 'poles' that carry the supply current to induce a magnetic field that penetrates the rotor. In a very simple motor, there would be a single projecting piece of the stator (a salient pole) for each pole, with windings around it; in fact, to optimize the distribution of the magnetic field, the windings are distributed in many slots located around the stator, but the magnetic field still has the same number of north-south alternations. The number of 'poles' can vary between motor types but the poles are always in pairs (i.e. 2, 4, 6, etc.).

Induction motors are most commonly built to run on single-phase or three-phase power, but two-phase motors also exist. In theory, two-phase and more than three phase induction motors are possible; many single-phase motors having two windings and requiring a capacitor can actually be viewed as two-phase motors, since the capacitor generates a second power phase 90 degrees from the single-phase supply and feeds it to a separate motor winding. Single-phase power is more widely available in residential buildings, but cannot produce a rotating field in the motor (the field merely oscillates back and forth), so single-phase induction motors must incorporate some kind of starting mechanism to produce a rotating field. They would, using the simplified analogy of salient poles, have one salient pole per pole number; a four-pole motor would have four salient poles. Three-phase motors have three salient poles per pole number, so a four-pole motor would have twelve salient poles. This allows the motor to produce a rotating field, allowing the motor to start with no extra equipment and run more efficiently than a similar single-phase motor.

There are three types of rotor:

• Squirrel-cage rotor

The most common rotor is a squirrel-cage rotor. It is made up of bars of either solid copper (most common) or aluminum that span the length of the rotor, and those solid copper or aluminium strips can be shorted or connected by a ring or some times not, i.e. the rotor can be closed or semiclosed type. The rotor bars in squirrel-cage induction motors are not straight, but have some skew to reduce noise and harmonics.

• Slip ring rotor

A slip ring rotor replaces the bars of the squirrel-cage rotor with windings that are connected to slip rings. When these slip rings are shorted, the rotor behaves similarly to a squirrel-cage rotor; they can also be connected to resistors to produce a high-resistance rotor circuit, which can be beneficial in starting

• Solid core rotor

A rotor can be made from a solid mild steel. The induced current causes the rotation.

 Speed control

The synchronous rotational speed of the rotor (i.e. the theoretical unloaded speed with no slip) is controlled by the number of pole pairs (number of windings in the stator) and by the frequency of the supply voltage. Before the development of cheap power electronics, it was difficult to vary the frequency to the motor and therefore the uses for the induction motor were limited. As an induction motor has no brushes and is easy to control, many older DC motors are being replaced with induction motors and accompanying inverters in industrial applications.The induction motor runs on induced current.speed of induction motor varies according to the load supplied to the induction motor.As the load on the induction motor is increased the speed of the motor gets decreased and vice versa.

Starting of induction motors

Three Phase

 Direct-on-line starting

The simplest way to start a three-phase induction motor is to connect its terminals to the line. This method is often called "direct on line" and abbreviated DOL.

In an induction motor, the magnitude of the induced emf in the rotor circuit is proportional to the stator field and the slip speed (the difference between synchronous and rotor speeds) of the motor, and the rotor current depends on this emf. When the motor is started, the rotor speed is zero. The synchronous speed is constant, based on the frequency of the supplied AC voltage. So the slip speed is equal to the synchronous speed, the slip ratio is 1, and the induced emf in the rotor is large. As a result, a very high current flows through the rotor. This is similar to a transformer with the secondary coil short circuited, which causes the primary coil to draw a high current from the mains.

When an induction motor starts DOL, a very high current is drawn by the stator, in the order of 5 to 9 times the full load current. This high current can, in some motors, damage the windings; in addition, because it causes heavy line voltage drop, other appliances connected to the same line may be affected by the voltage fluctuation. To avoid such effects, several other strategies are employed for starting motors.

Star-delta starters

An induction motor's windings can be connected to a 3-phase AC line in two different ways:

• wye (star in Europe), where the windings are connected from phases of the supply to the neutral;
• delta (sometimes mesh in Europe), where the windings are connected between phases of the supply.

A delta connection of the machine winding results in a higher voltage at each winding compared to a wye connection (the factor is ). A star-delta starter initially connects the motor in wye, which produces a lower starting current than delta, then switches to delta when the motor has reached a set speed. Disadvantages of this method over DOL starting are:

• Lower starting torque, which may be a serious issue with pumps or any devices with significant breakaway torque
• Increased complexity, as more contactors and some sort of speed switch or timers are needed
• Two shocks to the motor (one for the initial start and another when the motor switches from wye to delta)

 Variable-frequency drives

Variable-frequency drives (VFD) can be of considerable use in starting as well as running motors. A VFD can easily start a motor at a lower frequency than the AC line, as well as a lower voltage, so that the motor starts with full rated torque and with no inrush of current. The rotor circuit's impedance increases with slip frequency, which is equal to supply frequency for a stationary rotor, so running at a lower frequency actually increases torque.

[edit] Resistance starters

A resistance starter and its 4MW / 11kV induction motor, driving a ball mill.

This method is used with slip ring motors where the rotor poles can be accessed by way of the slip rings. Using brushes, variable power resistors are connected in series with the poles. During start-up the resistance is large and then reduced to zero at full speed.

At start-up the resistance directly reduces the rotor current and so rotor heating is reduced. Another important advantage is the start-up torque can be controlled. As well, the resistors generate a phase shift in the field resulting in the magnetic force acting on the rotor having a favorable angle^{[citation needed]}.

 Autotransformer starters

such starters are called as auto starters or compensators, consists of an auto-transformer.

Series Reactor starters

In series reactor starter technology, an impedance in the form of a reactor is introduced in series with the motor terminals, which as a result reduces the motor terminal voltage resulting in a reduction of the starting current; the impedance of the reactor, a function of the current passing through it, gradually reduces as the motor accelerates, and at 95 % speed the reactors are bypassed by a suitable bypass method which enables the motor to run at full voltage and full speed. Air core series reactor starters or a series reactor soft starter is the most common and recommended method for fixed speed motor starting. The applicable standards are [IEC 289] AND [IS 5553 (PART 3) ]

Single Phase

In a single phase induction motor, it is necessary to provide a starting circuit to start rotation of the rotor. If this is not done, rotation may be commenced by manually giving a slight turn to the rotor. The single phase induction motor may rotate in either direction and it is only the starting circuit which determines rotational direction.

For small motors of a few watts the start rotation is done by means of a single turn of heavy copper wire around one corner of the pole. The current induced in the single turn is out of phase with the supply current and so causes an out-of-phase component in the magnetic field, which imparts to the field sufficient rotational character to start the motor. Starting torque is very low and efficiency is also reduced. Such shaded-pole motors are typically used in low-power applications with low or zero starting torque requirements, such as desk fans and record players.

Larger motors are provided with a second stator winding which is fed with an out-of-phase current to create a rotating magnetic field. The out-of-phase current may be derived by feeding the winding through a capacitor, or it may derive from the winding having different values of inductance and resistance from the main winding.

In some designs the second winding is disconnected once the motor is up to speed, usually either by means of a switch operated by centrifugal force acting on weights on the motor shaft, or by a positive temperature coefficient thermistor which after a few seconds of operation heats up and increases its resistance to a high value, reducing the current through the second winding to an insignificant level. Other designs keep the second winding continuously energised during running, which improves torque.

Control of speed in induction motor can be obtained in 3 ways:

1.scalar control 2.vector control 3.direct torque control

Direct on line starter

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A direct on line starter, often abbreviated DOL starter, is a widely-used method of starting electric motors. The term is used in electrical engineering and associated with electric motors. There are many types of motor starters, the simplest of which is the DOL starter. The direct on line starter can be considered as a switch. When the motor is required to run, the starter supplies the full supply voltage (such as 400V, 50 Hz, 3-phase in the UK) to the motor. The motor will start as quickly as it can. A DOL motor starter is distinct from a simple relay in that it will also contain protection devices, and in some cases, condition monitoring.

DOL starting is sometimes used to start small water pumps, compressors, fans and conveyor belts. In the case of an asynchronous motor, such as the 3-phase squirrel-cage motor, the motor will pull a high starting current until it has run up to full speed. This starting current is commonly around six times the full load current, but may as high as 12 times the full load current. For this reason, larger motors will normally be soft started or run on variable speed drives in order to minimise disruption to the power supply.

Contents [hide] 1 DOL reversing starter 2 Safety devices within the starting circuit 3 See also 4 External links

[edit] DOL reversing starter

Most motors are reversible or, in other words, they can be run clockwise and counter-clockwise. A reversing starter is an electrical or electronic circuit that reverses the direction of a motor automatically. Logically, the circuit is composed of two DOL circuits; one for clockwise operation and the other for anti-clockwise operation. The case of three phase motor inter changing of any two phases will do the same

[edit] Safety devices within the starting circuit

These devices are used to protect the motor as well as the user of the motor being operated:

1. Overload coil The overload coil, also known as a thermal overload, is designed to open the starting circuit and thus cut the power to the motor in the event of the motor drawing too much current from the supply. The overload coil is a normally closed device which opens due to heat generated by excessive current flowing through the circuit. Thermal overloads have a small heating device that increases in temperature as the motor running current increases. A bi-metallic strip located close to the heater deflects as the heater temperature rises until it mechanically causes the device to trip and open the circuit, cutting power to the motor should it become overloaded. A thermal overload is basically a circuit breaker that will accommodate the brief high starting current of a motor whilst being able to accurately protect it from a running current overload. This is because the heater coil and the action of the bi-metallic strip introduces a time delay that affords the motor time to start and settle into normal running current without the thermal overload tripping. Thermal overloads can be manually or automatically resettable depending on their application and have an adjuster that allows them to be accurately set to the motor run current.

2. KM1 No-Volt coil The No-Volt coil serves a safety purpose of preventing a motor from restarting automatically after a power failure. This coil is connected in parallel across the start switch (which is a normally open switch) in the control circuit. The no-volt coil is energized once the start switch is initiated and the energized coil keeps current flowing through the control circuit. In the event that the power being supplied to the motor is interrupted, the motor will stop, and the No-Volt coil will become de-energized. In order for the motor to be restarted, the start switch must be initiated and therefore restarting the motor, and re-energize the energize the no-volt coil, re-starting the cycle. Only once the no-volt coil is energized, will current remain flowing in the control circuit.

…………………………………………………………………………………………………………………………………………………………………

What is a star delta starter and how does it work? In: Electrical Engineering, Wiring and Electricity, Industrial Electricity and Electronics [Edit categories]

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The starting current of any heavy electric motor can be more than 4 times the normal load current it draws when it has gained speed and has reached its normal running output power and temperature.

So, if it were started simply when connected in DELTA, the starting current would be huge and - just to be able to start the motor, not to run it normally - would require:

• large circuit breakers, big enough to allow the start-up surge current to pass without immediately shutting it off. (But the breakers would then be much too big to be able to protect the motor from over-current faults whilst it is running normally.)
• very thick 3-phase power service cables. (But the cable would then be much bigger than is necessary whilst the motor is running normally.)
• very large coils and contacts on the relays or contactors used to control the motor. (But they would then be much bigger than is necessary whilst the motor is running normally.)

One solution to this problem is to start the motor in STAR and then, when the motor has gained sufficient speed, change its connections to DELTA to allow the motor to run at its full speed and torque from then on. It's a bit like using the gears of an automobile.

Update: Electronic motor-control systems, which offer soft-starts in DELTA configuration, are now replacing the use of manual or semi-automatic star-delta starters.

Technical explanation

When the windings of a 3-phase motor are connected in STAR:

• the voltage applied to each winding is reduced to only (1 /._'/_'3) [1 divided by root three] of the voltage applied to the winding when it is connected directly across two incoming power service line phases in DELTA.
• the current per winding is reduced to only (1 /._'/_'3) [1 divided by root three] of the normal running current taken when it is connected in DELTA.
• so, because of the Power Law V [in volts] x I [in amps] = P [in watts],
  
  the total output power when the motor is connected in STAR is:
  
  P_{S =} [V_L x (1/._'/_'3)] x [I_D x (1/._'/_'3 )] = P_D x (1/3) [one third of the power in DELTA]
  
  where:
  V_L is the line-to-line voltage of the incoming 3-phase power service
  I_D is the line current drawn in DELTA
  P_S is the total power the motor can produce when running in STAR
  P_D is the total power it can produce when running in DELTA.
• a further disadvantage when the motor is connected in STAR is that the total output torque is only 1/3 of the total torque it can produce when running in DELTA.

………………………………………………………………………………………………………

Why use star-delta connections for a three phase motor? In: Electrical Engineering, Wiring and Electricity [Edit categories]

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Whichever way it is connected, no matter whether it is in a star configuration or in a delta configuration, a 3-phase motor's start-up current can be more than 4 times its normal running current.

If the star configuration is used when first switching-on power to a 3-phase motor, a much smaller "start-up surge" is forced onto the power lines than if it were switched-on directly in the delta configuration.

So "using star for start-up" achieves very worthwhile purchase cost savings because smaller circuit breakers and thinner 3-phase line wire sizes can be installed to supply power to the motor.

However, leaving it running in star has a major disadvantage: the motor can never deliver as much power and torque as when it is running in delta.

For that reason a 3-phase motor was usually started in star mode and then - after reaching a steady speed - switched over to run in delta mode to achieve its maximum power output.

The explanation for this is easier to understand if you draw a sketch of the wirings and their connections, but unfortunately we cannot use diagrams when giving an answer here! Anyway, if you draw the circuit diagram for the windings connected in a "star" or "Y" configuration, it should look like a three-pointed star, with a phase input power line attached to each point of the star.

Thus, when a 3-phase motor's three windings are connected in a star configuration, the current from each individual phase power input line goes directly into one winding and is then series-connected to both of the other two windings via the star's "center-point".

If you draw the circuit diagram for a delta configuration, it should look like a triangle with a phase power input line attached to each point of the triangle.

Thus, when a 3-phase motor's three windings are connected in a delta configuration, each winding is effectively connected directly to two phase supply lines. The third phase supply line is also connected to that winding, but indirectly via the other two windings. They are connected in series to one another, and that series pair is connected in parallel across the first winding, to form the "delta".

The much lower starting current is the main reason why a three-phase motor was usually started in star mode and then - after gaining a steady speed - was switched over to run in delta mode to achieve its maximum power output.

Update: Electronic motor-control systems, which offer soft-starts in DELTA configuration, are now replacing the use of manual or semi-automatic star-delta starters.

Technical explanation

When the windings of a 3-phase motor are connected in STAR:

• the voltage applied to each winding is reduced to only (1 /._'/_'3) [1 divided by root three] of the voltage applied to the winding when it is connected directly across two incoming power service lines in DELTA.
• the current per winding is reduced to only (1 /._'/_'3) [1 divided by root three] of the normal running current taken when it is connected in DELTA.
• so, because of the Power Law V [in volts] x I [in amps] = P [in watts],
  
  the total output power when the motor is connected in STAR is:
  
  P_{S =} [V_L x (1/._'/_'3)] x [I_D x (1/._'/_'3 )] = P_D x (1/3) [one third of the power in DELTA]
  
  where:
  V_L is the line-to-line voltage of the incoming 3-phase power service
  I_D is the line current drawn in DELTA
  P_S is the total power the motor can produce when running in STAR
  P_D is the total power it can produce when running in DELTA.
• a further disadvantage when the motor is connected in STAR is that its total output torque is only 1/3 of the total torque it can produce when running in DELTA.

For more information please see the answers to the Related Questions shown below.

How does a DOL three phase motor starter work? In: Electrical Engineering, Wiring and Electricity, Industrial Electricity and Electronics [Edit categories]

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A DOL Starter means Direct On-Line starter. In this type of starting a 3-phase motor, full voltage is applied to the motor through relays and contactors. Its is the most common type of 3-phase motor starter used.

It has a "closing circuit" and an "opening circuit". The closing circuit is for applying the supply to the motor and the opening - or "tripping" - circuit protects the motor by cutting-off (or "tripping") power to the motor from the supply lines if there is any overload condition, a single phasing fault, etc.

For more information please see the answers to the Related Questions shown below.

What are the applications of a star delta starter? In: Electrical Engineering, Industrial Electricity and Electronics [Edit categories]

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The Star/Delta starter is probably the most commonly used reduced voltage starter, but in a large number of applications, the performance achieved is less than ideal, and in some cases, the damage and interference is much worse than that caused by a Direct On Line starter.

The Star/Delta starter requires a six terminal motor that is delta connected at the supply voltage. The Star Delta starter employs three contactors to initially start the motor in a star connection, then after a period of time, to reconnect the motor to the supply in a delta connection. While in the star connection, the voltage across each winding is reduced by a factor of (1 /._'/_'3) [1 divided by root three]. This results in a start-current reduction to (1 /._'/_'3) [1 divided by root three] of the DOL start current and a start torque reduction to one third of the DOL start torque.

If there is insufficient torque available while connected in star, the motor can only accelerate to a partial speed compared to the full speed it would reach if connected in delta. When the timer operates (set normally from 5-10 seconds), the motor is disconnected from the supply and then reconnected in delta, resulting in full line voltage running currents and torque.

The transition from star connection to delta connection requires that the current flow through the motor is interrupted. This is termed "Open Transition Switching" and with an induction motor operating at a partial speed compared to full load speed, there is a large current and torque transient produced at the poi, unless proper protection methods are used, can cause severe damage to the supply service's infrastructire and to other connected equipment.

If there is insufficient torque produced by the motor when running in star, there is no way to accelerate the load to full speed without switching to delta and causing those severe current and torque transients. These must be allowed-for in the design of the motor and its starting system if they are to have an economic useful life.

Update: Electronic motor-control systems, which offer soft-starts in DELTA configuration, are now replacing the use of manual or semi-automatic star-delta starters.

Technical explanation

When the windings of a 3-phase motor are connected in STAR:

• the voltage applied to each winding is reduced to only (1 /._'/_'3) [1 divided by root three] of the voltage applied to the winding when it is connected directly across two incoming power service lines in DELTA.
• the current per winding is reduced to only (1 /._'/_'3) [1 divided by root three] of the normal running current taken when it is connected in DELTA.
• so, because of the Power Law V [in volts] x I [in amps] = P [in watts],
  
  the total output power when the motor is connected in STAR is:
  
  P_{S =} [V_L x (1/._'/_'3)] x [I_D x (1/._'/_'3)] = P_D x (1/3) [one third of the power in DELTA]
  
  where:
  V_L is the line-to-line voltage of the incoming 3-phase power service
  I_D is the line current drawn in DELTA
  P_S is the total power the motor can produce when running in STAR
  P_D is the total power it can produce when running in DELTA.
• a further disadvantage when the motor is connected in STAR is that its total output torque is only 1/3 of the total torque it can produce when running in DELTA.

For more information please see the answers to the Related Questions shown below.

Re: What is the d/f between DOL & star delta starter & automatic star delta starter?
Answer # 1	A DOL starter connects the motor terminals directly to the power supply. Hence, the motor is subjected to the full voltage of the power supply. Consequently, high starting current flows through the motor. This type of starting is suitable for small motors below 5 hp (3.75 kW). Reduced- voltage starters are employed with motors above 5 hp. Although DOL motor starters are available for motors less than 150 kW on 400 V and for motors less than 1 MW on 6.6 kV. Supply reliability and reserve power generation dictates the use of reduced voltage or not To reduce the starting current of an induction motor the voltage across the motor need to be reduced. This can be done by autotransformer starter, star-delta starter or resistor starter. Now-a-days VVVF drive used extensively for speed control serves this purpose also.   Is This Answer Correct ?    169 Yes 19 No	3

WHAT MAKES AN ISLAMIC SCHOOL ISLAMIC? ::: DEVELOPING THE CURRICULUM

WHAT MAKES
AN ISLAMIC SCHOOL
ISLAMIC?

:::
 DEVELOPING THE CURRICULUM

[A paper presented by B. Aisha Lemu at the National Conference of NAMIS (Nigerian Association of Model Islamic Schools) in Ibadan, 4th/5th April 2003.]

Schools are places where knowledge is imparted. But what knowledge? Knowledge simply means "things that are known". There is no way that all things that are known can be taught to students in primary and secondary schools, or even in universities.

Therefore there has to be selection of knowledge. To establish a school curriculum, groups of experts over the years have identified various fields of knowledge which are given names like languages, maths, history, physics, art, technology, literature, geography and so on.

Over the centuries and in different civilizations the curriculum in schools has changed. These changes reflected not only the knowledge that was available at the time, but also what a particular civilization at a particular time thought was important for the next generation. That is to say, the curriculum reflected its values. For example in ancient China the imperial examinations for recruitment into the civil service focused on philosophical essays and poetry, with the idea that Government administrators should be scholars, aesthetes and cultivated gentlemen. In ancient Greece the curriculum included music, whose harmonies were seen to be related to mathematics. In the England of my youth, we were automatically taught Latin, the language of the Romans. Even though it is a long-dead language, exposure to the logic of its grammar and to its literature was considered to be an essential civilizing intellectual experience, and until well into the twentieth century every "educated" person including those holding high rank in the civil service would have been taught Latin and possibly also ancient Greek.

These subjects were in the 20th Century largely displaced by the scientific and technological subjects that have come to dominate our modem world.

The status of religious education has also drastically changed. In medieval Europe as in much of the Muslim world religious studies were heavily weighted in the Curriculum. Later, during the European Colonial rule religion was a core subject in Christian schools all over the world. In many parts of the Muslim world today there are still Madrassahs or Qur'anic Schools which focus on religious education exclusively.

We who are engaged in the establishment of Islamic Model Schools in the 21st Century should not therefore neglect intensive thought and productive debate on what we should be teaching our children that will equip them to think and live as Muslims fully engaged with our contemporary world.

The question is how to do this? For many people, an Islamic Model School is a school exclusively for Muslims with an all-Muslim staff, where the Qur'an, Islamic Studies and Arabic are all taught alongside the National Curriculum. The School uniform and the school assembly conform with Islamic norms. We then call it an "Islamic" school and hope that we are turning out authentic Muslims.

There is no doubt that the widespread movement for Islamic Schools and Islamiyyah Schools is a big step forward. If we do not control our children's education we lose control of our future as a Muslim community. Many of the Model Islamic Schools are doing very well and producing good results in academics and Islamic knowledge as well as good behaviour of their students.

This is certainly an improvement on what prevails nowadays in Government Schools. However this cannot be regarded as the summit of our aspirations, for several reasons.

Firstly, due to shortage of financial commitment and competent manpower resources among Muslims in Nigeria, the great majority of Islamic Model Schools are at Nursery/Primary level. We should not forget that it is at secondary level that most students start religious questioning and may or may not develop serious religious interest and commitment. There is a need for academic research on what happens to the products of the Islamic primary schools when they go on to secular secondary schools and universities. Does their Islamic primary school education influence their later attitudes and way of thinking? If so in what ways?

Secondly, is it sufficient just to teach so-called "secular subjects" and so-called "religious subjects" under one roof and call it "Islamic education" without a serious attempt to develop a clear relationship between the two - that is, an Islamic perspective on modem knowledge, and a modem perspective on our understanding of the divine message?

At the secondary level there is enormous scope for this process -particularly in boarding schools where students may be involved in co-curricular activities in the evenings and at weekends.

New Horizons College, Minna, was established by the Islamic Education Trust in 1994, and for the first 7 years it functioned as a dual system school - that is, modem subjects and Islamic subjects taught under the same roof.

What follows is a case study of how over the past two years we have been trying to integrate aspects of the curriculum in an effort to develop a holistic approach to knowledge.

I shall therefore take it as a kind of Case Study of how we are approaching the issue of Curriculum, which is the topic of this paper.

::: New Horizons College: A Case Study

Our starting point is to recognize that we in Nigeria, as a former colonized country, tend still to be very imitative. Changes in education in the Western world take place and within a few years we follow, without really analyzing the benefits and losses of such a change. "Western" means "advanced" and of course we all want to be "advanced".

Secondly, throughout the Muslim world, Islamic education itself has been, so to speak, self-imitative for centuries. A teacher is expected to teach what he was taught, using the same methods by which he was taught. Hence it is extremely difficult to get most Islamic Studies and Arabic teachers to look at any textbook other than the textbook from which they learned, or to consider any change in the method which might speed up the pupils' learning.

Therefore people running schools, and especially Islamic Schools, tend not to think beyond the boundaries of their own experience or look for solutions by examining the problems from broader perspectives.

As an example of this I have put as an appendix to this paper a copy of the 9-dot problem, with which some of you may be familiar. (I request you to wait until after this presentation before attempting it.)
The point is to show that we allow ourselves to be mentally confined by boundaries that do not really exist.

Perhaps we should therefore not focus so much on the curriculum as on what do we want to be the outcomes of our curriculum, and then find the ways to achieve those outcomes, which may be innovative and experimental. In this way we may build up our own curriculum for Model Islamic Schools.

New Horizons College was the great challenge for us and it was from the time we started admitting boarders, 2,5 years ago, that we began to take a fresh look at the concept of a Model Islamic School, and to go beyond just teaching two unrelated educational curricula under the same roof.

When you have boarders on your premises 24 hours a day for 36 weeks of the year it soon becomes apparent that the children of well-to-do Muslim parents today are often exposed to all kinds of influences, modem and traditional, some of them very harmful, and that many suffer from parental neglect and undesirable peer group pressure. Some parents transfer their children into Islamic boarding schools precisely because they have gone off the rails and are out of control - even to the extent of taking drugs.

Therefore unless we can change their way of thinking and make an impact on their perceptions, we shall not be able to achieve the outcomes we desire, and our students will be just like any other students in Nigeria except that they know some Arabic and perhaps can recite the Qur'an a little better than others.

This is a serious issue, which those establishing Islamic Schools have to address.

Therefore in our own case we set up an Islamic Orientation Board composed of key individuals within the school and the IET to consider the question: "What makes an Islamic School Islamic?" Is it just a name or does that name actually describe something that is going on in the school?

In the broadest sense the formal and informal curriculum includes everything that a student is expected to experience at school, both in and out of class.

Therefore we examined the entire school environment and experience, from early morning until night to identify what needed to be done to promote Islamic manners, morals and understanding, including personal relationships between staff and staff, between staff and students and between students among themselves.

We looked into the disciplinary system to lay more emphasis on counseling and recognition of good behaviour rather than on punishment.

We looked into the motivation and development of staff so as to encourage them to become role models for the students. We encouraged team games and inter house activities to develop team spirit. We encouraged many clubs an societies to develop the children's practical skills and talents. We used the mosque not only for prayers but for all forms of nasiha and enlightenment by the students as well as staff and invited outsiders.

Then we looked at the aspect of the formal curriculum. How feasible is it to "Islamise" the teaching of the National Curriculum subjects such as English, Maths, the Sciences, the Social Sciences, Technical and Vocational subjects? And what do we really mean by "Islamizing" knowledge? Knowledge is surely knowledge - if it is true knowledge it is automatically "Islamic".

Therefore, apart from the massive problems of "Islamizing" the syllabus and the textbooks and the teacher training and orientation, the question arises "Is all this necessary?"

It seems to me that we do not have any quarrel with most of the factual component of the National Curriculum. It is more a matter of "what do you deduce from this information?" "How does this relate to other things that I know or believe as a Muslim?"

In other words we want students to develop Islamic perspectives on knowledge, we want them to perceive "Allah's signs in the universe" in whatever they may be studying - whether it be Geography or Physics or Food and Nutrition.

Therefore while it would be ideal for all teachers to be able to stimulate "Conceptual Transformation of Knowledge" as applied to their subjects in the classroom, we cannot depend on that for a number of reasons relating to way the modem universities teach and chum out graduates who have memorized handouts but have not been taught how to think.

::: Islamic Perspectives:

We have therefore found it productive to introduce a separate subject called "Islamic Perspectives". This subject is taught by people who may or may not be regular full-time members of staff, but who have actually understood the approach. Such teachers must have broad knowledge of the arts and sciences, up-to-date knowledge of the modem world, and a sympathetic understanding of the students' existing ways of thinking (in other words it should generally not be the Islamic Studies teacher!). Islamic Perspectives is the meeting place of the Qur'an with so-called secular knowledge. The person teaching it must have thought deeply about this and integrated them in his own mind.

The task of the teacher is to expose the students to various books, video cassettes or concepts which stimulate their thinking and relate these to what we understand from the Qur'an. The lesson will therefore include a lot of discussion, because we are not just focusing on the factual information but also on its;
interpretation and understanding in relation to other knowledge and in the light of the divine revelation.

When you have helped the student to internalize these Islamic insights you are on the way to developing young people who think and feel and act like Muslims. This is because you .are teaching the method of Conceptual. Transformation of Knowledge (CTK) based on which the students can themselves apply it to any knowledge which they are taught, whether in school or later at university. It is a kind of inoculation against the secular approach. One might call it "Do it yourself CTK".

The materials to be used in this process may vary as we change them
whenever something better appears. At present we are using the following books and cassettes.
JSS 1: Islamic Manners and Social Conduct (Lemu, Orire and Rodrigo) IET Publications.
JSS 2: Wonders of Allah's Creation (Harun Yahya) Ta Ha Publishers, London.
JSS 3: Steps on the Right Path (Selected Hadith on the Moral Teachings of Islam) (edited by Lemu and Dolley - IET Publications). To this we plan shortly to add a new book of Selected Qur'anic passages in English translation entitled "Getting the Message".
SSS 1: For Men of Understanding (Harun Yahya) Ta Ha Publishers, London.
SSS 2/3: Islam the Natural Way (Abdulwahid Hamed) MELS, London
Video Cassettes: Any of the cassettes on aspects of Science by Harun Yahya. The Global Environment (BBC Video Series) Legacy (ITV Series on great civilizations of the past and their intellectual and moral legacies.) Empire of Faith (USA) on the Civilization of Islam The Trials of Life (David Attenborough, BBC) and other programmes by the same presenter on Animal and Plant behaviour.

::: Train-the-Trainers Course in Da’wah and Dialogue:

We also concluded that every student who graduates from our school should be able to convey the message of Islam to others (Muslims or non-Muslims) and to be skilled and confident in dialogue with non-Muslims in particular.

Therefore for 2 years (SSS1 and SSS2) the students have one period a week of training in this subject. They learn comparative religion, how to deal with misconceptions about Islam, how to handle areas of disagreement among Muslims, how to present Islam, public speaking and individual dialogue.

Since it is a Train-the-Trainers Course, students are required to learn and practice teaching others - which greatly helps them to remember the material and topics they cover.

::: Arabic and Qur'anic Arabic:

When we started the school we naturally taught Arabic language to all students in the expectation that they would all study it for 6 years and take it as a WAEC/SSCE subject.

Unfortunately, the university people who drew up the Arabic syllabus for 6-3-3-4 made it suitable only for students of specialist Arabic institutions, by including a large component of Arabic Literature, which cannot be covered in the time available in the regular secondary schools which can only allow 3 periods a week for Arabic.

A year ago we conducted a workshop on this problem with NATAIS (Nigerian Association of Teachers of Arabic and Islamic Studies) but it seems they are not ready to make a move to popularize the subject by cutting down the literature component.

This is disappointing as students do not want to register for a subject in which they have little chance of getting credits in SSCE. We have therefore had to drop it for science students in senior classes and make it compulsory for Arts students only up to SSS 2. However, students are taking a greater interest with the recent provision of an Arabic Language Laboratory and Arabic Club.

However in order to ensure that every student is helped in the reading and understanding of the Qur'an, we have the following subjects for the whole 6 years:

Qur'anic Arabic and understanding the meaning of the Qur'an

Qur'an: Reading, Recitation with Tajwid and Memorization (with regular competitions).


Since the latter is time-consuming it cannot all be done during the regular teaching periods. Therefore boarders do it in the mosque after Subh prayers and 3 ;times a week in the evenings, while parents of day students are asked to ensure their children cover the same syllabus with home tuition or local Islamiyyah schools.

::: Subject Weighting

If we add together the number of periods per week given to the Islamic related subjects (Islamic Studies, Islamic Perspectives, Arabic, Qur'anic Arabic, Da'wah and Dialogue and the Qur'an with Tajwid) it comes to about ten, out of 38 periods per week - that is just over one-third. To this, should be added the time spent on Qur'anic reading and recitation after Subh prayers and before Maghrib about 3 days a week.

Yet in spite of this time taken out of the so-called secular curriculum the students are getting among the best results in the country in their WAEC and NECO exams.

Social Interaction between boys and girls:
When we established the school we would have preferred it to be single sex, but we felt it would be unfair to offer our style of education to boys only or girls only, therefore we took both. However for both social and academic reasons we decided to divide our school block into 2 sections, for boys and girls, but with shared laboratories, computer center etc. Likewise we have separate hostels for boys and girls, and boys and girls do afternoon games on alternate days.

However, we have other activities where the boys and girls participate together, such as clubs and societies, debates, quizzes and so on. We take into account that in the adult world in Nigeria, including the universities, there is no gender segregation, therefore, it is important for both boys and girls to learn to interact in a sensible and responsible manner in an Islamic environment as training for later life.

::: Non-Muslim Teachers:

There is also the question of employing non-Muslim teachers in a Muslim school. Some people are totally opposed to this idea but this is not our view, based on 9 years of experience of employing teachers of various nationalities and religions on condition that they do not in any way undermine our objectives as an Islamic school. The employment of non-Muslim teachers was initially based on the need to find the best teachers available, who in some cases are non-Muslims.( However some of our Christian teachers have shown greater dedication and loyalty than many others, and set standards for young Muslim teachers to emulate. Secondly, we recognize that we live in a multi-religious society and a multi-religious world, where we live and work together with non-Muslims. There is therefore no point in isolating our students from non-Muslims and creating barriers instead of developing inter-religious co-operation and trust. This is based on our teachers' understanding that we are an Islamic school and wish all teachers to uphold and promote its Islamic moral ethos. We raise this issue in the teachers' job interviews and we have not had problems with it.

::: Conclusion:

This paper has covered most of the key areas of our experience in developing an Islamically-oriented secondary school.

Of course there are many other models for an Islamic school, and some proprietors may choose different areas of emphasis and formulate different policies. This is entirely healthy as it gives each school the chance to test its ideas and approaches, evaluate the outcomes, and change or fine-tune them in the light of experience.

Some people urge standardization of the curriculum in Islamic schools, but I think this is premature and should be entirely voluntary. There is nothing to stop private Islamic schools meeting to discuss curriculum and policies with a view to sharing ideas, exchanging materials and learning from one another. But we are developing a very new approach to education which draws its inspiration from the challenges of the Qur'an and relates them to modem knowledge and the realities of our situation today. We need more thinkers and educationists to be free to continue the search for the best practice and to test their ideas against realities.

This process is now being encouraged at international level by an organization called IBERR (International Board for Educational Research and Resources) headed by Br. Yusuf Islam with an Advisory Board drawn from the U.K., USA, South Africa, Australia, Canada, Nigeria, Malaysia, Kuwait and the-United Arab Emirates (UAE). It has done a lot of work to bring the ideas of Islamization of Knowledge formulated over the past 25 years into the practical realm of curricula, textbooks and guidelines for all the stakeholders in Islamic Schools: proprietors. Boards of Governors, Principals, Teachers and parents.

Meanwhile, NAMIS is playing a very important role in bringing together the hundreds of Islamic Model Schools all over Nigeria to exchange ideas and materials and to benefit from each others' experience as our own contribution to the worldwide movement for the development of an Islamically-based educational system.

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