Variable frequency drives

Variable Frequency drive commonly known as VFD is widely used for speed control. VFDs have been an efficient method of controlling the speed of electric motors and hence are also known as variable speed drives. These are required for carrying out VFD automation for various types of electric motors.

How does a Variable Frequency Drive (VFD) work?

In order to understand a VFD, a general understanding of Electric motor is essential. An electric motor rotates its rotor as per the parameters achieved by the voltage and frequency of the electric power supplied to the motor. Internationally there are few different electric system voltage such as 400V (3 Phase), 380 V (3 phase) etc. and 50 or 60 Hertz frequency. By varying the voltage and/or frequency the performance of the motor including the speed varies. It is generally difficult to change the voltage or frequency without ancillary equipment. A variable frequency drive is used to achieve the voltage and frequency variations efficiently. The normal electric power supply is supplied to the VFD and the output of the VFD is fed to the electric motor. There are controls available in the VFD which can be adjusted to control the speed of the motor

Major components of a Variable Frequency Drive (VFD)

The major components for controlling an AC motor are as explained below:

  1. AC to DC converter. The incoming AC is first converted to DC. (This is also known as a rectifier)
  2. DC to AC converter. The DC is converted into AC of another frequency (This is also known as a power inverter)
  3. DC capacitors to absorb frequency variations
  4. Heat sinks to dissipate the heat
  5. Control systems to adjust the output

Our solutions for your requirements of VFD Automation

We carry out supply and installation of Variable Frequency Drives of major manufacturers. VFD Automation consists of the correct VFD and its control systems. We need the details of your motor including, voltage, frequency, capacity (kW), application etc. to decide the required VFD. Accordingly, the selected VFD will be installed by us including electrical cabling to the motor from the power supply through the VFD. Please find an example of Carbon Monoxide (CO) monitoring system with exhaust fans controlled using a VFD.

How to select the right VFD for your motor?

Even though there are numerous manufactures and models of VFDs, the basic selection process is same for all of them. In order to select the right VFD, you’ll need the following details

  1. Electrical parameters such as Voltage, Frequency, current and kW rating
  2. If you require more than one motor to be controlled by one VFD, the ratings of all the motors have to be considered
  3. Torque requirements of the load. The Variable Speed Drives are not ideal for high starting load
  4. Starting torque and regular running torque need to be considered. If you have different loads at different times, please consider maximum and minimum torque requirements.
  5. Additional protection required against over current and short circuit.
  6. Firstly the motor has to be selected based on your application and thereafter variable frequency drive has to be selected to suit the motor.
  7. Type of required VFD automation for automatic control of the motor.