Experiment- 01
AIM: Study of three phase VSI (1800 mode) fed three-phase induction motor.
APPARATUS REQUIRED:
SL
NO.
NAME OF
EQUIPMENT
TYPE
RATING
MANUFACTURE’S QUANTITY
NAME
1
1ɸ variac
AC
0-270 V
AE
1
2
Multi-meter
AC/DC 0-600 V, 10 A
fluke
1
3
Ammeter
MC
Supreme
1
4
DSO
Keysight
1
5
Voltage probe
Keysight
1
5/10 A
300 V
6
RATINGS OF MOTOR-GENERATOR SET:
Machine
Induction motor
DC Generator
Type
Power
Voltage
Speed
Current
3-phase
1 hp
200/415V
1440 RPM
1.8 A
-1 hp
220 V
1500 RPM
7A
THEORY:
V/F control algorithm is one of the basic control modes which is widely accepted. V/F is
abbreviated from voltage/frequency. V/F control is an induction motor control method which
ensures the output voltage proportional with the frequency, so it maintains a constant motor flux,
preventing weak magnetic and magnetic saturation phenomenon from happening.
V/f control of induction motor means varying the speed of motor by changing frequency but, at
the same time, keeping the V/f ratio constant. This is important to maintain the same air gap flux
in the motor and hence a constant torque.
Department of Electrical Engineering
Page | 1
CIRCUIT DIAGRAM:
PROCEDURE:
1) Connect the circuit diagram as shown in Fig.1
2) Press the Reset switch if RESET LED glows.
3) Connect the output of inverter to the motor terminal.
4) Switch on the power supply.
5) Apply voltage through Variac.
6) Press switch to increase set speed (V/f ratio), corresponding actual motor is displayed.
7) Note down the reading after each increment.
8) Increase the load and tabulate frequency, modulation index and actual speed.
9) Measure the line voltage or output voltage of inverter.
10) Reset the function by pressing o/c Trip reset.
11) Discharge the capacitance voltage through CDR by breeder resistor.
CALCULATION:
Va0=ma*(Vd/2)* 3/√2
Vd= Voltage across capacitance
ma= Modulation index
Va0= Fundamental line-line peak voltage
f= reference frequency
Find ratio of V/f and calculate error in output voltage.
Department of Electrical Engineering
Page | 2
OBSERVATION TABLE:
Sl.
No.
Load
Reference
Modulation Voltage(V) Speed(rpm) REMARKS
Frequency(Hz)
Index
GRAPHS:
1. Plot V vs f .
2. Plot modulation index vs speed.
Fig. 01. Plot of Voltage versus frequency.
Fig. 02. Plot of modulation index versus speed.
CONCLUSION:
With increase in modulation index, output voltage increases and therefore speed is increasing.
PRECAUTIONS:
1)
2)
3)
4)
5)
6)
Wear shoes that cover the feet.
Don’t wear loose clothes.
Maintain a work space clear of extraneous material such as books, papers, and clothes.
Don’t use broken connecting wires.
Turn off the power switch to equipment before making connections.
The motor input current should not exceed its rated value.
Department of Electrical Engineering
Page | 3
Indian Institute of Technology (ISM), Dhanbad
Dept. of Electrical Engineering
Experiment No. 01
Date:
TITLE:
Name:_______________________________
Sem: _____________
Year: __________
Adm. No. ___________________
CIRCUIT DIAGRAM:
OBSERVATION TABLE:
Sl.
No.
Load
Reference
Frequency(Hz)
Modulation
Index
Voltage(V)
Speed(rpm)
REMARKS
_________________________
(Signature of the teacher)
Department of Electrical Engineering
Page | 4