EXPERIMENT 4:
Induction 3 Phase Slip Ring Motors
Objectives:
1. Connect a three phase asynchronous slip ring motor using various value of
external rotor resistance
2. Measure the standstill current of the motor with various starter resistance in
circuit
3. Select or change, the direction of rotation of the motor
Instrument/Component
1 3-phase slip ring asynchronous motor
1 Magnetic powder brake
1 Control unit for brake
1 Rubber Coupling sleeve
1 Coupling guard
1 Shaft end guard
1 Rotation reversing switch
1 Start for slip ring motors
1 Cut out switch, 3 pole
1 Multimeter
1 Set of connection cables
1
Circuit Diagram
L1
L2
L3
N
PE
A
U1
V1
W1
W2
U2
V2
M
K
L
M
Fig 4.1
2
ROTATION REVERSING SWITCH
1
L3
0
V
W
L2
2
U
L1
L1
I
0
DANGER 415 Volts
L2
L3
MOTOR PROTECTION SWITCH 3 POLE
I
0
TORQUE
Nm
min -1 X 1000
M OL n
x1 x2 x3
CONTROL UNIT FOR MAGNETIC POWDER BRAKE
CONTR. MODE
BRAKE
MOTORS
min-1
REVOLUTIONS
0
Nm
SET/START VALUE
L1 L2 L3
3
POWER
R
M
STARTER
100W
Ω
U2
L
K
V1
W2
U1
L
M
V2
W1
R
M
SE2662-3W
K L M
M
U2 V2 W2
U1 V1 W1
STARTER
100W
Ω
L
R
M
STARTER
100W
Ω
L
L1
L2
L3
N
Ground
A
U1
V1
W1
W2
U2
V2
M
K
L
M
Fig 4.2
4
Exercise
1. Construct the circuit as shown in the fig. 4.1.
2. Set the control unit as follows:
a) Speed
n = 1500 rpm
b) Torque
M = 5Nm
c) Operating Mode M = constant
Range on multimeters
Armature current IA = 3A
Adjust the starter to position 1
Adjust the start/set value, so that after switching on the motor under load, a
start up is prevented.
3. Measure the standstill (when the rotor stops) at each starter position. Enter
the value into the table 4.1
Starter
1
2
3
4
5
6
I (A)
Table 4.1
4. Now set the control unit as follows:
a) Speed
b) Torque
c) Operating Mode
n = 1500 rpm
M = 2Nm
M = constant, a.c
Range on multimeter: Armature current IA = 3A
Operate the motor
5. Set the value on the control unit to 1.9 Nm
Measure the motor current and speed, at each setting of the starter switch,
commencing at position 1.
Enter the values into table 4.2
5
Starter
1
2
3
4
5
6
N (rpm)
I (A)
Table 4.2
6. Construct the circuit shown in Fig 4.2
7. Set the control unit as in step 4 above. Turn the switch to position 1 and then
2. State the direction of rotation in each case
Question
1. Evaluate the result obtained in step 3
2. Comment on the relationship between the motor current, motor speed and
starting resistance, by reference to the results obtained in step 5 above
3. Explain how the rotation reversal is achieved as the switch is turned to
position 1 then 2 as in step 7
6