Variable Frequency Drive for Single-Phase and Three-Phase Motors
Variable frequency drives (VFDs)—also referred to as AC drives, variable speed drives, inverters, and motor drives—regulate the voltage and frequency that a power supply delivers to a connected motor. These controller devices are suitable for use with single-phase and three-phase motors, adjusting their output speed to enhance process operations and energy efficiency.
Due to their critical function in motorized applications, when choosing a variable frequency drive, there are several key factors to keep in mind. The following article provides a high-level overview of VFDs and their selection considerations.
Overview of VFDs
VFDs control the output speed, torque, direction, and horsepower of connected electric motors by varying their energy input—specifically the voltage and frequency. They are available in three main types, each of which is characterized by the technique employed to alter the energy input. The three types are:
- Pulse Width Modulation (PWM), which changes output frequency by changing the width of the output voltage waveform
- Current source inverter, which converts constant input DC current to a variable output AC current
- Voltage source inverter, which converts constant DC voltage to variable AC voltage
Using a VFD on a Single-Phase Motor vs. a Three-Phase Motor
Industry professionals can use VFDs with single-phase or three-phase motors. However, depending on the specifications of the motorized application, it may be better to use one type of motor over the other. For example:
- Single-phase motors are suitable for applications requiring lower power levels
- Three-phase motors are suitable for applications requiring lower RPMs and higher power efficiencies
Although most VFDs available are used with three-phase motors, there are VFDs produced specifically for use with single-phase motors. This disparity in availability is due to the difference in winding configuration between the two types of motors and the resultant price differential—three-phase motors tend to be less expensive than single-phase motors.
Industrial Applications of VFDs
VFDs find use in a wide range of industrial applications regulating the power to connected motors.
Single-phase VFDs are used for low power applications that typically need less than one horsepower. Some of the use cases for single-phase VFDs are:
- Airflow controllers and blowers
- Centrifugal pumps
- Electric shavers
- Non-industrial fans
- Vacuum cleaners
Three-phase VFDs are used for a wide range of high power industrial equipment and systems, including:
- Air compressors
- Centrifugal pumps
- Freezers and refrigerators
- Heating, ventilation and air conditioning (HVAC) systems
- Heavy duty machinery, such as drill presses, crushers, conveyors, grinders, lathes, mixers, sanders, saws, etc.
- Lifting equipment, such as cranes and hoists
How to Choose the Right VFD for Your Motor
Some of the key considerations to keep mind when choosing a VFD for a motor are:
- Number of motors needing control
- Input power in voltage and number of phases (single-phase or three-phase) of each motor
- Horsepower and current rating of each motor at full load
- Operating requirements, such as motor speed or torque required
- Operating environment
- Interface requirements for operator input to the motor drive system
Variable Frequency Drives (VFDs) From Gainesville
Gainesville Industrial Electric (GIE) is the largest independent motor distributor in Georgia. To support our motor products, we also offer a line of VFDs from TECO Westinghouse Motor Company, a highly experienced designer and manufacturer of motors and VFDs.
TECO Westinghouse Low Voltage AC Drives
The low voltage AC drives offered from TECO-Westinghouse range in output power from ¼ HP to 1,000 hp and include:
- L510 micro AC drives: 1/4 hp to 3 hp
- N3 compact drives: 1/2 hp to 75 hp
- E510 NEMA 4/12 AC drives: 1 hp to 25 hp
- F510 fan and pump AC drives: 5 hp to 250 hp
- A510 Heavy duty AC drives: 1 hp to 250 hp
- EQ7 series AC drives: 1 hp to 1,000 hp
TECO Westinghouse Medium Voltage AC Drives
VersaBridge® medium voltage AC drives are suitable for industrial applications that require power output from 1,500 hp to 40,000 hp. They find use in a variety of industries for rugged applications, such as mining, oil and gas, and utility and power generation.