Electrical Motor Controls & Disconnects

Also known as a motor drives, a motor controller converts power from a power supply to a mechanical system. There are several types available to accommodate the type of motor you are using, including variable speed drives, line starters, and motor starters. Motor controllers regulate motor speed, torque, and position outputs. The four basic motor controller drive types include:

AC

• Modify input power to motors by adjusting frequency of power to the motor
• Regulate output speed and torque

DC

• Modify input power by adjusting constant or alternating current source to pulsed, direct current output of varying pulse duration or frequency

Servomotor

• Modify input power in the same way as DC drives
• May be AC or DC driven
• Controller supplies control signals to the drive

Stepper

• Modify input power by adjusting constant or alternating current source to pulsed or “stepped” current output

They can use either manual or automatic switches, which refers to the motor starting and stopping. With a manual motor controller, if an electrical overload or failure occurs, the device trips, switches off, and stops the motor. Once it switches off, the user must manually turn it back on, making this type best suited for small, simple motors. On the other hand, an automatic controller will start again automatically.

A motor disconnect switches loads on and off with manual operator controls. It can disconnect the motor for service or maintenance.

A pole refers to a magnetic field of force generated by a permanent magnet or current passing through a coil of wire. The voltage requirement determines the number of poles to match the voltage configuration and HP rating. Most industrial requirements use 3 or 6 pole switches. More poles mean the controller can more precisely control stepper motor output.

A breather drain provides ventilation in hazardous locations to allow the air inside an enclosure to breathe with the surrounding atmosphere and allow any moisture to drain. This prevents interior condensation build up in the motor control.

Each type of motor control sees use in various industrial applications. AC motor controllers and drives see use primarily in process applications to control speed of pumps, fans, and blowers. DC controllers see use primarily to control motor speeds and torques for machine tools, electric vehicles, and pumps. Servomotor and stepper controls see use in machine tools, micro positioning, and robotics.