Page 171 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

EXERCISE 71 : Start, run & load ac 3 phase Squirrel
cage & Wound rotor Induction motors

for performance testing

Objectives

At the end of this exercise you shall be able to:
• measure phase resistance of the winding
• carry out the No-load test on three phase Squirrel cage induction motor
• carry out the blocked test on three phase Squirrel cage induction motor
• calculate the efficiency of 3 phase induction motor.

Requirements

Tools/Instruments Equipments/Machines
• Combination pliers 150mm -1 No. • 3Ф Squirrel cage Induction
• Screw driver 100mm -1 No. Motor 3HP, 415V -1 No.
• D.E. spanner set 20mm -1 Set. • DOL starter 3HP,415V -1 No.
• Electrician knife 75mm -1 No. • Autotransformer 16A,500V -1 No.
• Series test lamp 60W -1 No. • ICTP 16A,500V -1 No.
• Voltmeter MI 500V -1 No. • Variable DC supply 0-30V, 5A -1 No.
• Ammeter MI 2A -1 No. Materials
• Voltmeter MC 30V -1 No. • PVC Copper wire 1.5mm -1 No.
2
• Ammeter MC 2.5A -1 No.
• Wattmeter 500V, 2.5A -1 Nos.

Procedure

TASK 1: To measure phase resistance of the motor winding
1 Note down the name plate details of the three phase Squirrel cage induction motor.

2 Check the no. of terminals of motor.
3 identify each phase winding, if six terminals are available.
4 Draw the circuit diagram for phase resistance measurement.
5 Make the connections as per circuit diagram Fig 1
Connections should be tight and neat.

6 Connect the variable DC supply to one phase winding if 6 terminals are available
7 Connect ammeter and voltmeter to the circuit.
8 Apply DC low voltage.
9 Read and record the ammeter and voltmeter readings in Table.

10 Calculate the resistance per phase as R= V/I
11 Connect low voltage DC to 2 terminals, if the motor has only three terminals out.
12 Calculate the resistance per phase based on three phase connection type of motor as given below;
13 Tabulate phase resistance in Table 1

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CITS : Power - Electrician & Wireman - Exercise 71