EXPERIMENT 2:
Part A
Shunt Wound Machine as a Motor
: Connection and Starting
Objectives:
1. Connect and operate a D.C shunt wound machine as a D.C shunt wound
motor with and without starter
2. Measure the starting current and the armature voltages
3. Deduce that the starter reduces the starting
Circuit Diagram
1. Without starter
L+
A
A1
E1
E2
V
M
A2
LPE
Fig 2.1
1
L1
I
0
L2
L3
MOTOR PROTECTION SWITCH 3 POLE
I
DANGER 415 Volts
ROTATION REVERSING SWITCH
1
W
L3
0
V
L2
2
U
L1
L1 L2 L3
2
TORQUE
Nm
M OL n
x1 x2 x3
CONTROL UNIT FOR MAGNETIC POWDER BRAKE
CONTR. MODE
BRAKE
MOTORS
min-1
REVOLUTIONS
0
Nm
SET/START VALUE
0
min -1 X 1000
POWER
R
M
STARTER
100W
Ω
A1
E1
A2
E2
L
UAUSG
0
1
A2
M/G
A1
START
SE2662-3A
E2
E1
ST7007-5A
-
+
-
+
2. With starter
L+
A
RA
A1
E1
E2
V
M
A2
LPE
Fig 2.1
Instrument/Component
1 D.C shunt wound machine
1 Magnetic powder brake
1 Control unit for brake
2 Rubber coupling sleeves
2 Coupling guard
1 Shaft end guard
1 Starter for D.C motors
1 Field regulator for D.C generators
1 Load resistance
2 Multimeter
1 Set of connection cables
3
Exercise
1. Copy the following detailed information from the ratings label of the D.C shunt
wound machine, which apply when operated as a shunt wound motor:
a)
b)
c)
d)
e)
Type
U
I
UE
IE
:……………………….
:……………………….V
:……………………….A
:……………………….V
:……………………….A
2. Connect the machine without starter, according to circuit diagram in Fig 2.1
3. Set the control unit as follows:
a) Speed
n
b) Torque
M
c) Operating mode n
= 3000 rpm
= 1Nm
= constant
Range on multimeters
a) Voltage
b) Armature current, IA
c) Exciter current, IE
= 300 V
=1A
= 0.3 A
4. Operate the motor and set the torque on the control unit to M=0.3 Nm.
Measure the starting current and the armature voltage. Enter the measured
values into Table 2.1
5. Connect the machine with starter, according to circuit diagram in fig. 2.2. The
settings on the control unit remain unchanged. Set the starting resistor to
100% (47 Ω) Measure the starting current and the armature voltage. Enter the
measured values into Table 2.1
Starter
Load
Starter Current Ia (A)
Armature Voltage UA (V)
R = 0Ω
M = 0.3 Nm
R = 47Ω
M = 0.3 Nm
Table 2.1
Questions
1. What is the purpose of the starter?
4
Part B
: Load Characteristics
Objectives
1. Connect and operate a D.C shunt wound machine as a shunt wound motor
for recording the load characteristics
2. Draw the load characteristic curve from the values obtained by measurement
and by calculations
3. Deduce from the load characteristics that the motor is most efficient at its
nominal speed and check the deduction by calculations
4. Describe the response of the shunt wound motor under various load
conditions
Circuit Diagram
L+
A
A
A1
E1
E2
V
M
A2
LPE
Fig 2.3
5
Instrument/Components
1 D.C shunt wound machine
1 Magnetic powder brake
1 Control unit for brake
2 Rubber coupling sleeves
2 Coupling guard
1 Shaft end guard
1 Starter for D.C motors
1 Field regulator for D.C generators
1 Load resistance
2 Multimeter
1 Set of connection cables
Exercise
1. Connect the circuit diagram shown in Fig 2.3
2. Set the control unit as follows:
a) Speed
b) Torque
c) Operating mode
n
M
M
= 3000 rpm
= 1Nm
= constant
Range on multimeters
a) Voltage
b) Armature current, IA
c) Exciter current, IE
= 300 V
=1A
= 0.3 A
3. Operate the generator. Set the D.C power supply to 220V
4. Set the control unit to the torque values given in the table, commencing at 0.3
Nm. Measure the speed, armature current and the exciter current. Enter the
values into table 2.2 below
5. Calculate the consumed electrical power
P1 = UA x Itot
Itot = IA + IE
6. Calculate the delivered mechanical power
P2 = 2πMN/60 this simplify to P2 = M.N/9.55
7. Calculate the efficiency of the motor, η = P2 / P1
Enter the calculated values into the table 2.2
6
8. From the results, measured and calculated, plot the graph of the load
characteristics.
a) N (rpm) vs M (Nm)
b) IA (A) vs M (Nm)
c) P2 (W) vs M (Nm)
d) ŋ vs M (Nm)
220
U (V)
M (Nm)
0.3
0.5
0.7
0.8
0.9
1.0
1.1
1.2
1.3
N (rpm)
IA (A)
IE (A)
Itot (A)
P1 (W)
P2 (W)
ŋ
Table 2.2
Question
1. From the characteristics result, describe the response of the speed of the
motor under load condition.
2. State the best efficiency with the corresponding values of torque and speed
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