Service of Drives


What is the definition of a “variable frequency drive”?

Service of Drives – A variable frequency drive, or VFD for short, is basically a motor controller. Its job is to vary and change the frequencies and the supply voltage of the related electric motor so that its speed can be kept in check when it is driven. A variable speed drive is known by many other names which include modifiable speed drive, modifiable frequency drive, AC drive, micro-drive and inverter.

Service of Drives – There is a directly proportional relationship between the frequency and the motor speed. Frequency is measured in hertz while motor’s speed is measured as revolutions per minute i.e. RPMs. In simpler words, the more speedy the frequency, the speedier the RPMs will be. If the requirements of the application are such that there is no need of running the motor at full speed, a variable frequency drive comes in handy by turning down the frequency and voltage so that it is all balanced and in accordance with the electric motors load. With time the application’s motor speed requirements can and do vary, and a variable frequency drives ensures that the speed is modified, turned up or down, and all of the requirements are met.

What is the working of a variable frequency drive?

Service of Drives – The converter is the very first part of a variable frequency AC drive i.e. VFD. Six diodes make up the composition of the converter. The working of these diodes is similar to the working of check valves which are part of a plumbing system. A diode restricts the movement or flow of current to only one direction. This direction is specified by an arrow that makes up a diode symbol. In the following example, voltage is the counterpart of pressure in a plumbing system. The example is such that if at a moment the A phase voltage has higher positivity as compared to B or C phase voltages then A phase diode will let the current to flow through it. If after that the B phase’s positivity becomes higher than that of A phase then that diode will open resulting in the closure of A phase diode. There will be the same working for the three diodes that are present on the side of the bus that is negative. After the opening and closing of all the diodes, we are able to get six current pulses. This configuration is known as a “six pulse variable frequency drive”. This is also the standard configuration that is typical for current variable frequency drives.

Benefits of using a VFD

Numerous advantages are provided by a variable frequency drive, which are listed as follows:

  1. The first one is the conservation of energy
  2. No more need of costly machineries for mechanical driving.
  3. Motor’s endurance and life is increased significantly
  4. The power line noises are lessened.
  5. There is also significant reduction in the danger of motor damage that occurs during the starting up and stopping.

Some of these benefits can be compromised as a result of poor practice, but the energy conservation is enough justification on its own.