DC Injection Braking for Industrial AC Motors

Why is DC injection braking so important in industrial applications that use AC motors?  Industrial AC motors run at high speeds so they can power heavy duty equipment and machinery.  Using high power motors is crucial to any operation that requires a reliable motor for speed and quality. AC motors are used in a variety of applications.  They can power fans, planers, conveyors, rolling mills, cut-off saws, wood hogs, rubber mills, presses, rock crushers, shredders, chippers, centrifuges, grinders, and other machines or equipment.

AC motors are often controlled at start-up with soft starters and/or controlled for accurate speed and torque while operating with AC motor drives.  Unfortunately, controlling these aspects of the motor’s operation doesn’t help much when the time comes to actually slow or stop the motor.

Since motors operate at high speeds, the rotor will continue to spin and spin (and spin some more) even after the power has been turned off.  So is waiting for the rotor to stop a problem?  It can be if this causes significant downtime in a plant or facility where efficiency is a priority.  If the AC motor must be stopped and restarted multiple times during the course of a work day, then this can result in a great loss of time overall.  And in any business….Time Equals Money!

DC Injection Brakes Provide a Long-Term Solution

DC injection brakes can be installed to rapidly and safely stop an AC motor.  There are also options for adjustable braking with closed-loop current control.  Unlike mechanical brakes, DC injection brakes do not wear because they are not exposed to friction during the braking process.  Therefore, high levels of torque can be delivered to stop the motor using controlled DC injection in two motor phases.  

How do they work?  These types of brakes inject DC voltage into the AC motor winding after the AC power/voltage has been disconnected.   Doing so provides a braking force to stop the rotor.  DC injection brakes can also be used for emergency braking, when the motor needs to be stopped immediately for whatever reason.  Whatever the purpose, DC injection brakes work well as an alternative to friction brakes because they can be installed away from the rotor along with other drives or motor switchgear.  They can easily be mounted in a convenient, remote location.  Friction brakes, however, must be mounted within the rotor area.  DC injection brakes can be integrated into the motor drive circuitry so it won’t be necessary for a human operator to control the braking unit.

Do you have an application that requires smooth fast braking for AC motors?   Check out our page about OP STOP DC injection brakes…
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