2 Switch ON power to both Now the field ON indicator should glow 3 Vary the pot

2 switch on power to both now the field on indicator

This preview shows page 43 - 49 out of 57 pages.

2. Switch ON power to both. Now the field ON indicator should glow. 3. Vary the pot and see the variation in speed. Keep the pot in middle of its range and record the waveform of armature voltage. 4. By varying P record armature voltage and speed for different values of firing angles. 5. Switch off power. TABULAR COLUMN SLN FIRING ANGLE ( ) ARMATURE VOL(V) SPEED (RPM)
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Power Electronics Laboratory Manual 10ECL78 Page 44 EXPECTED WAVEFORMS
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Power Electronics Laboratory Manual 10ECL78 Page 45 Ex.No:11 SPEED CONTROL OF UNIVERSAL MOTOR AIM : Speed control of a Universal Motor and induction Motor APPARATUS: 1. EC08A-1 2. EC08B 1 (With 15V Step down transformer) 3. RPS 0 to 30V-1, 0 to - +15v 4. CRO and PROBE-1 5. DMM-1 THEORY A universal motor is basically an electric motor capable of working on either dc or single-phase ac at approximately the same speed and output. The stator and rotor windings of the motor are connected in series through the rotor commutator. Therefore the universal motor is also known as an ac series motor or an ac commutator motor. Speed of this motor can be varied by varying the applied voltage by using either a controlled rectifier or an ac voltage controller. Universal motors are generally designed to operate at high speeds in the range 10000 to 20000 r.p.m. The universal motors normally work on AC supply but their performance is much better on DC supply. The inherent disadvantage of universal motors is that normally they operate at high speed and at low speed universal motors are very bulky. Single phase induction motor speed can be controlled over a limited range by varying the applied voltage using an ac voltage controller. The ac motors have a number of advantages, they are almost 20 to 40% lighter than equivalent dc motors, they are inexpensive and have low maintenance compared to dc motors but they require complex control circuits. CONTROL CIRCUIT
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Power Electronics Laboratory Manual 10ECL78 Page 46 POWER CIRCUIT PROCEDURE Make the connections of firing circuit and power circuit as shown in the figure TESTING THE FIRING CIRCUIT 1. Connect dual power supply and 15v AC. DO NOT CONNECT FIRING CIRCUIT TO POWER CIRCUIT. 2. Keep the pot meter in middle position and check waveforms at A, B, C, D, E, F & G. 3. Change the pot meter position and observe the change in firing angle. 4. Turn off DC & AC supply. TESTING THE POWER CIRCUIT 1. Connect firing circuit to power circuit. 2. Switch ON power to both. Now the field ON indicator should glow. 3. Vary the pot and see the variation in speed. Keep the pot in middle of its range and record the waveform of armature voltage. 4. By varying P record armature voltage and speed for different values of firing angles. 5. Switch off power.
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Power Electronics Laboratory Manual 10ECL78 Page 47 POWER CIRCUIT WAVE FORMS
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Power Electronics Laboratory Manual 10ECL78 Page 48 Ex.No:12 SPEED CONTROL OF STEPPER MOTOR AIM: Speed control of stepper motor.
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  • Fall '14
  • H N SHANKAR

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