ed lab manual

EEE 552: CONTROL SYSTEM LAB MANNUAL

EEE 752 ELECTRIC DRIVES

LABMANUALLIST OF EXPERIMENTS

Note: Minimum 10 experiments are to be performed from the following out of which at least three should be simulation based.

(A) Hardware Based Experiments:

1. To study speed control of separately excited dc motor by varying armature voltage using single phase fully controlled bridge converter.

2. To study speed control of separately excited dc motor by varying armature

voltage using single phase half controlled bridge converter.

3. To study speed control of separately excited dc motor using single phase

dual converter (Static Ward-Leonard Control).

4. To study speed control of separately excited dc motor using MOSFET/

IGBT chopper.

5. To study closed loop control of separately excited dc motor.

6. To study speed control of single phase induction motor using single phase ac voltage controller.

7. To study speed control of three phase induction motor using three phase ac voltage controller.

8. To study speed control of three phase induction motor using three phase current source inverter.

9. To study speed control of three phase induction motor using three phase voltage source inverter.

10. To study speed control of three phase slip ring induction motor using static rotor resistance control using rectifier and chopper.

11. To study speed control of three phase slip ring induction motor using static scherbius slip power recovery control scheme.

(B) Simulation Based Experiments (using MATLAB or other software)

12. To study starting transient response of separately excited dc motor.

13. To study speed control of separately excited dc motor using single phase fully / half controlled bridge converter in discontinuous and continuous current modes.

14. To study speed control of separately excited dc motor using chopper control in motoring and braking modes.

15. To study starting transient response of three phase induction motor.

16. To study speed control of three phase induction motor using (a) constant/V/F control (b) ConstantVoltage and frequency control.EXPERIMENT NO.: 1 OBJECT: To study speed control of single phase induction motor using single phase ac voltage Controller (TRIAC).

APPARATUS REQUIRED:S.No.Apparatus NameRatingsQuantity

1Single phase induction motor

2Ac regulator use of triac kit

3Tachometer

4Voltmeter

5Connecting Leads

6Power Supply

CIRCUIT DIAGRAM:The circuit diagram of speed control of single phase induction motor using single phase ac voltage Controller (TRIAC) is shown in the figure given below:-

Figure: Circuit diagam of speed control of 1- induction motor using TRIAC

THEORY:The circuit connections are made as shown in figure. The capacitor C is charged through the controlled resistor R. The resistance is used to protect the potentiometer by limiting the capacitor charging current. The diac conducts when the voltage on the capacitor reaches its break over voltage of sufficient amplitude and width to trigger the triac. Because the operation across on each half cycle of the applied voltage the triac , therefore is triggered and conducts on each half cycle of the input supply voltage.PROCEDURE:1. Make the connections as shows.

2. Switch on the power supply.

3. Charge the potentiometer resistance R.

4. Observe motor speed by tachometer.

5. Observe voltage between its terminals.

6. Repeat steps 3, 4,and 5.

OBSERVATION TABLE:S.NO.Firing AngleVoltage across the motorMotor speed

1

2

3

4

5

RESULT:The graph between the motor speed and terminal voltage is as shown in the figure:

Figure: The graph between the motor speed and terminal voltagePRECAUTIONS: 1. All wiring connections should be right and tight.2. All steps should be followed carefully.

3. Readings and calculations should be proper.

4. Dont touch the live terminals.

EXPERIMENT NO.: 2OBJECT:To study speed control of separately excited dc motor by varying armature voltage using single phase half controlled bridge converter.APPARATUS REQUIRED:S.No.Apparatus NameRatingsQuantity

1Separately exited DC motor

2Single Phase Half Controlled Bridge

3Firing Pulse Generator

4Resistive Load(Lamp)

5Inductive Load(Choke)

61:10 Attenuator for CRO

7Isolated ac supply for CRO

8Voltmeter

9Ammeter

10Lamp Holder

11Connecting Leads

12Power Supply

CIRCUIT DIAGRAM:

Figure: Circuit diagram of single phase half controlled bridgeThe circuit diagrams of single phase half controlled bridge firing circuit to fire the SCRs of the bridge are shown in the figures.

Figure: firing circuit to fire the SCRsTHEORY:The use of single phase fully controlled bridge converter in industries for speed control of DC motor, temperature control of electrical furnaces, light dimmer, battery chargers etc. In all these applications the fire angle is controlled and feedback circuit is made depending on the requirements. The used firing circuits is tried to make simple, friendly and easily understandable.

There are two circuits used in single phase half controlled bridge converter:1. single phase half controlled bridge

2. firing circuit to fire the SCRs of the bridge

In a cycle of source voltage , the thyristor SCR1 receives gate or firing pulse from to and the thyristor SCR2 receives gate or firing pulse from (+) to 2. When the thyristor SCR1 is fired at , motor gets connected to source through SCR1 and D1 and terminal voltage is equal to source voltage. The armature current flows and D2 gets forward biased at . Consequently armature current freewheels through the path D1 and D2 and the motor terminal voltage is zero. Armature current becomes zero as conduction of D2 reverse biases the SCR1 until the SCR2 is fired at (+). Next cycle of the motor terminal voltage stars in similar procedure. The RC networks R1 and C1, R2 and C2, R3 and C3 and R4 and C4, are used to protect the concerned thyristors.OBSERVATION TABLE:S.No.Speed, N in rpmArmature Voltage, Va in volts

RESULT:The study speed control of separately excited dc motor by varying armature voltage using single phase half controlled bridge converter were studied.PRECAUTIONS:1. All wiring connections should be right and tight.

2. All steps should be followed carefully.

3. Readings and calculations should be proper.

4. Dont touch the live terminals.5. Voltage should not exceed more than 250 V.

EXPERIMENT NO.: 3OBJECT:To study speed control of separately excited dc motor by varying armature voltage using single phase fully controlled bridge converter.



2Single Phase fully Controlled Bridge

3Firing Pulse Generator

4Resistive Load(Lamp)

5Inductive Load(Choke)

61:10 Attenuator for CRO

7Isolated ac supply for CRO

8Voltmeter

9Ammeter

10Lamp Holder

11Connecting Leads

12Power Supply

CIRCUIT DIAGRAM:

Figure: Circuit diagram of single phase fully controlled bridgeThe circuit diagrams of single phase fully controlled bridge firing circuit to fire the SCRs of the bridge are shown in the figures.

Figure: firing circuit to fire the SCRsTHEORY:The use of single phase fully controlled bridge converter in industries for speed control of DC motor, temperature control of electrical furnaces, light dimmer, battery chargers etc. In all these applications the fire angle is controlled and feedback circuit is made depending on the requirements. The used firing circuits is tried to make simple, friendly and easily understandable.

There are two circuits used in single phase fully controlled bridge converter:

1. single phase fully controlled bridge2. firing circuit to fire the SCRs of the bridge

In a cycle of source voltage , the thyristors SCR1 and SCR3 receive gate or firing pulse from to and the thyristors SCR2 and SCR4 receive gate or firing pulse from (+) to 2. When the thyristors SCR1 and SCR3 are fired at , motor gets connected to source through SCR1 and SCR3 and terminal voltage is equal to source voltage. Armature current becomes zero untill the SCR2 and SCR4 are fired at (+). Next cycle of the motor terminal voltage stars in similar procedure. The RC networks R1 and C1, R2 and C2, R3 and C3 and R4 and C4, are used to protect the concerned thyristors.

OBSERVATION TABLE:S.No.Speed, N in rpmArmature Voltage, Va in volts

RESULT:The study speed control of separately excited dc motor by varying armature voltage using single phase half controlled bridge converter were studied.

PRECAUTIONS:1. All wiring connections should be right and tight.2. All steps should be followed carefully.3. Readings and calculations should be proper.4. Dont touch the live terminals.5. Voltage should not exceed more than 250 V.

EXPERIMENT NO.: 4OBJECT:To study closed loop control of separately excited dc motor. APPARATUS REQUIRED:S.No.Apparatus NameRatingsQuantity


2Rheostat

3Tachometer

4Voltmeter

5Ammeter

6Connecting Leads

7Power Supply

CIRCUIT DIAGRAM:The circuit diagram of closed loop control of separately excited dc motor is shown in the figure.

Figure: Closed loop speed control of separately excited dc motor

Figure: Closed loop current control of separately excited dc motor

THEORY:DC motor speed control required in several industries like thread manufacturing, cutting machines etc. In heavy industries machine soft starting is essential so that is achieved by motor speed control like in crane operation to avoid hammering to object or machine. DC motor speed control can achieve by using variac, rheostat and by power electronics devices like as SCR.

There are two methods to control the speed of DC motor as follows:

1. Speed of the DC motor can be controlled above the normal range of speed by varying the resistance in the circuit included in the form of a rheostat as a variable resistance (armature control).

2. Speed of the DC motor can be controlled above the normal range of speed by decreasing the flux i.e. by decreasing the current in the field circuit by including as external resistance in the form of a rheostat as a variable resistance (field control).

The basic approach of closed loop control of speed of separately excited dc motor below and above the base speed is explained as shown in the figure. Such a drive will operate on a constant field and variable armature voltage below the base speed and at constant armature voltage with variable field, are therefore fed from fully controlled rectifier. The drive will de-accelerate due to load torque only because of an inner current control with current limiter.OBSERVATION TABLE:S.No.Speed, N in rpmArmature Voltage, Va in volts

RESULT:The study of closed loop control of separately excited dc motor was studied.

PRECAUTIONS:1. All wiring connections should be right and tight.2. All steps should be followed carefully.3. Readings and calculations should be proper.4. Dont touch the live terminals.5. Voltage should not exeed more than 250 V.

EXPERIMENT NO.: 5OBJECT:To study speed control of three phase slip ring induction motor using static rotor resistance control using rectifier and chopper.


1

2

3

4

5

6

7

CIRCUIT DIAGRAM:The circuit diagram of speed control of three phase slip ring induction motor using static rotor resistance control using rectifier and chopper is shown in the figure.

Figure: Circuit diagram of speed control of three phase slip ring induction motor using static rotor resistanceTHEORY:The speed control by means of slip variation can be activated by employing a variable resistance in the rotor circuit. The maximum torque does not depend upon the value of rotor resistance. The rotor resistance influences slip at which maximum torque occurs.

The rotor speed of a 3- slip ring induction motorcan be controlled by the following methods:

1. By inserting the rotor resistance

2. By varying the stetor voltage

3. By slip power recovery scheme

4. By injecting a voltage of slip frequency in the rotor circuit

The operation of speed control by changing the rotor resistance is similar to the speed control of DC shunt motor by inserting the resistance in the armature circuit. The main disadvantage of this method is that the efficiency is low due to the large ohmic losses in the rotor resistance.

The operation consists of 2 parts:(a) Power circuit

(b) Control circuit

In power circuit the 3 phase rectifier is used to convert 3 phase rotor supply to DC supply. An inductor is connected in series with the DC supply for the smoothness of DC. An Mosfet is provided for chopper control mounted on a proper heat sink. All the points are brought out on the front panel for interconnections.

The control circuit generates driver output for driving the Mosfet in Chopper mode. The duty cycle is varied for changing the speed. Soft start and soft stop is provided for the driver output.OBSERVATION TABLE:S.No.Speed (rpm)Bulb on/off

RESULT:The study of speed control of three phase slip ring induction motor using static rotor resistance control using rectifier and chopper was studied.

PRECAUTIONS:1. always keep some resistance in between the rotor circuit.

2. the ON time control pot must be in OFF position because no control is

possible if Mosfet has burnt out.

EXPERIMENT NO.: 6OBJECT:To study speed control of three phase induction motor using three phase ac voltage controller.


1

2

3

4

5

6

7

CIRCUIT DIAGRAM:The circuit diagram of speed control of three phase induction motor using three phase ac voltage controller is shown in the figure.

Figure: 3- ac voltage controller feeding a 3- induction motorTHEORY:3- induction motors are admirably suited to fulfill the demand of loads requiring substantially a constant speed. Several industrial applications, however, need adjustable speeds for their efficient operation. The object of the present section is to describe the basic principles of speed control techniques employed to 3- induction motors through the use of power electronics converters. The various methods of speed control through semiconductor devices are as under:

1. Stator voltage control

2. Stator frequency control

3. Stator voltage and frequency control

4. Stator rotor resistance control

5. Slip power recovery scheme

STATOR VOLTAGE CONTROL

The operation consists of 2 parts:

(a) Power circuit

(b) Control circuit

In power circuit the 3 phase rectifier is used to convert 3 phase rotor supply to DC supply. An inductor is connected in series with the DC supply for the smoothness of DC. An Mosfet is provided for chopper control mounted on a proper heat sink. All the points are brought out on the front panel for interconnections.

The control circuit generates driver output for driving the Mosfet in Chopper mode. The duty cycle is varied for changing the speed. Soft start and soft stop is provided for the driver output.

The motor torque Te is proportional to the square of the stator supply voltage. A reduction in the supply voltage will reduce the motor torque and therefore speed of the drive. If the motor terminal voltage is reduced to KV1 where K