AC Drives

AC Variable Frequency Drives (also known as VFD, or Inverter) control the speed of an AC Induction motor by varying both the voltage and frequency of its output power to the motor. They only work with 3-phase motors, not single-phase motors.   VFD drives coupled with AC motors are quickly replacing DC drives and DC motors as the preferred method of varying the speed of an electric motor due to the much lower cost and maintenance of the AC systems. 

Run 3-Phase Motors on Single Phase Power

VFD drives can run 3-phase motors from single-phase supply.  This is possible on smaller sized motors, usually up to about 5 to 10 HP.  This makes it possible to run 3-phase motors with variable speed from standard home AC power.  Three phase motors have several advantages over single-phase motors including:

  • Lower Cost - 3-phase motors are lower cost than comparable single-phase motors
  • Higher Reliability  3-phase motors do not have capacitors or internal switches
  • More Efficient - 3-phase motors are more energy efficient compared to single phase motors
  • Variable Speed - it is possible to vary the speed of a 3-phase motor, which cannot be done with typical single-phase motors

Power Savings and Efficiency

VFDs also significantly reduce power consumption and inrush current.  They can replace soft starts, and older reduced-voltage starters and auto-transformer systems to provide a slow acceleration on startup.  This greatly reduces inrush current, which not only save money on utility bills, but also reduces wear and tear on the motor and driving equipment.  Additionally, by only running the motor at the speed required for the job at hand, a significant savings in power consumption can be realized.

Remote Control and Network Integration

Most VFDs sold today have options for many types of network control and easily integrate into SCADA systems.  Options include Ethernet, WiFi, Bluetooth, RS-485, RS-232, Modbus, CANopen, DeviceNet, Profibus, and more. And all VFDs have built in ability to connect a remote start, stop, reverse, and speed pot, as well as remote keypads.   Bluetooth and WiFi options allow control directly from a smart-phone.

Caldwell Electric is an Authorized Distributor of Several Brands

Caldwell Electric is an authorized distributor for Lenze / AC Tech, Techtop, Weg, and Worldwide drives. We have been repairing and selling drives, electric motors and motor controls for more than 40 years and can offer expertise in selecting drives for specific applications as well as diagnosing problems with motors and motor control systems.