AC Drives

AC drives, also known as variable frequency drives (VFDs), are an essential component in modern industrial control systems. These devices control the speed, torque, and direction of AC motors, which are widely used in a variety of applications such as pumps, fans, and conveyors. The use of AC drives results in energy savings, increased productivity, and improved process control. AC drives work by converting the incoming AC power into a controlled DC voltage. This DC voltage is then converted back into a controlled AC voltage to drive the motor. The control of the AC voltage results in the control of the motor speed and torque. The speed of an AC motor can be controlled by adjusting the frequency of the AC voltage supplied to the motor. AC drives use pulse width modulation (PWM) techniques to generate a variable frequency AC waveform. This waveform is then applied to the motor, resulting in the control of motor speed.

Frequently Asked Questions

Always by the Full Load amps of the motor, and the type of application. VFDs have ratings ND or LD (Normal or Light Duty) and HD (Heavy Duty) both of which are key to figuring out sizing. Typically 110-120% overload in a light duty or normal duty, and 150-180% overload in a heavy duty application.

  • Speed Control of an AC synchronous motor, as well as direction control
  • Under speeding or over speeding a motor
  • Running in a current limiting mode to protect a motor
  • In some approved applications, you can use a VFD to take single phase input, and convert it to three phase, all while controlling the voltage and frequency output

Primarily it is a Diode Bridge Rectifier setup to convert the AC coming in to DC, where it stores the DC in Capacitors and pulls from the capacitors through IGBTs (insulated gate bi-polar transistors) converting the DC back to AC in a controlled PWM (pulse width modulated form.)

If you want piece of mind in knowing your motor & system is setup correctly, start-up by a Wistex professional tech is highly recommended. Ensuring the best level of protection, without the nuisance trips, or having a system automatically reset at times are just the few considerations to take in order ensure your soft start & VFD are configured to your systems' needs..

When an authorized company and technician working on your VFD or Motor Control performs the start-up and fills out the appropriate paperwork with the Manufacturer, your warranty is extended. Typically manufacturers of VFDs or Soft starters offer a warranty of 18 months from shipment, or 1 year from date of install, whichever occurs first. If the start-up is certified and warranty paperwork is filed, the date can be extended to 2-3 years overall depending on the manufacturer.