What is VFD and its Working?
Today we will understand what is VFD, how VFD works. How can we adjust the speed of the motor and why do we need VFD. What is VFD and working?
Full-Form of VFD - Variable Frequency Drive
What is the use of VFD? Why do you use VFD?
There are some machines in the company whose speed we have to increase more or less according to the machine operator. At that time we can adjust the speed of the machine by changing the speed of the motor.
Motor speed means to increase or decrease the RPM of the motor.
Full-Form of RPM - Revolutions Per Minute
This means the number of times the rotor of the motor is rotating in a minute is called the RPM of the motor and with the help of VFD, we can easily change the RPM of the motor.
How is the motor speed adjusted?
We have two ways to change the speed of an electrical motor.
1. We can change the RPM of the motor by increasing the number of poles of the motor. The lower the poles of the motor, the higher will be the RPM of the motor. The poles of the motor are at least up to 2. Now as the poles increase, the speed of the motor decreases accordingly.
2. We can increase or decrease the RPM of the motor by adjusting the frequency of the electrical supply going to the motor.
Out of both of the methods, we use the second method more of changing the frequency of the electrical supply.
Because to change the motor RPM in the first method, we have to change the number of poles, which is fixed. Poles are always dependent on the slot of the winding of the motor, we cannot change it once the motor is designed.
So now we are left with only one way, that now we will change the motor speed by changing the frequency of the electrical supply given in the motor.
Gearbox motor controller
Apart from this, we can also adjust the gearbox on the motor to increase the speed of the machine, but adjusting the gearbox is very laborious.
If we adjust the speed with the help of the gearbox, then we will have to stop the machine again and again. But with the help of VFD, the speed can be changed easily.
What is VFD- Variable Frequency drive?
VFD is a motor controller which changes the speed of the motor by changing the voltage and frequency going to the motor.
Why is VFD called a motor controller?
VFD is called motor controller because inside VFD we have to fill in the details of the motor, which means some parameters have to be filled. With the help of which we can easily control the motor.
For example how much voltage should go to the motor if the motor stops after taking how much current. Apart from this, we can control the motor completely with the help of VFD. That's why we call VFD a motor controller.
Working of Variable Frequency Drive
The electrical supply that we were giving on the motor, now we will first give that supply to VFD and we will connect the supply which will come out from VFD to the motor.
Now we can adjust the output supply coming out of the VFD according to our needs and can easily change the RPM of the motor.
The more frequency we supply to the motor, the more the speed of the motor, and the lower the frequency we give, the lower the RPM of the motor.
Also Read - VFD vs Soft Starter for motor | Difference between soft starter and VFD?
How does VFD work?
There are 3 main parts inside the variable frequency drive.
1) Converter Unit of Variable Frequency Drive
2) Filter Unit of Variable Frequency Drive
3) Inverter of Variable Frequency Drive
Now let us assume that we have supplied 3 phase 440 voltage 50 HZ to VFD. Our AC supply will first go to the converter unit of the VFD.
Converter Unit of Variable Frequency Drive
In the converter unit, our AC supply is converted into a DC supply. The converter unit consists of a rectifier circuit, whose function is to convert AC supply into DC supply.
After the DC supply is released from the converter unit, this supply comes to the filter unit.
Filter Unit of Variable Frequency Drive
The work of the Filter Unit which we have got DC supply now. It is not pure DC. Some of the properties of AC supply remain in this. So now the filter unit converts the DC supply received from the converter unit into pure DC supply.
We get a pure DC supply from the filter unit, now the last work is done by the inverter unit.
Inverter of Variable Frequency Drive
The work of the inverter is to change that DC voltage back to AC voltage and give AC supply to the motor.
But, now the inverter which will produce the AC supply, we can adjust it according to our need.
Meaning if we have to run the motor at low speed. So now we will go to the parameter of VFD and reduce the frequency. Due to which the inverter unit of VFD will also supply low frequency to our motor. In this way, we can easily run the motor at more or less RPM and control the speed of the electrical industrial motor.
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