Three Phase Variable Frequency Drive (VFD)
Aim:
To study the operation of Three Phase Variable Frequency Drive (VFD)
Learning Objectives:
-
To study speed variations of a Three phase IM
-
To understand operation of V/F control using three phase Inverter
Apparatus:
-
Experimental kit
-
DSO/CRO (Unearthed)
-
Multimeter
-
Patch cords and DSO probes
Experimental Setup
Experiment Video
Procedure
-
Switch on the power supply
-
Adjust freq. of Drive signals to 30 Hz using pot.
-
Observe Gate Drive signals 1to6 one by one & plot timing diagram.
-
Measure I/P of error amplifier using dc voltmeter. Due to feedback circuit they have almost same values. & o/p of error amplifier almost 0.
-
Measure Ac voltage fed to induction motor between any to phases on terminal strip provided on back side of box. Vary the speed by varying frequency. Calculate V/F ratio. Vary freq 20Hz, 25 Hz, 35 Hz, 40 Hz & repeat step 5. & verify that V/F ratio is constant. You can also measure speed of motor using tachometer for different frequencies.
-
Theoretically , Speed = 120 * FREQ./ P & P=No. of poles= 4
-
Now Switch off the power supply & Change phase sequence of induction motor & Switch on power supply. Motor will rotate in opposite direction.
Observation Table
|
Sr.No. |
Frequency f (Hz) |
Voltage(V) |
V/f Ratio |
Speed N (RPM) |
|
1 |
|
|
|
|
|
2 |
|
|
|
|
|
3 |
|
|
|
|
|
4 |
|
|
|
|
|
5 |
|
|
|
|
Comments
Post a Comment