Dynamic brake system for a BLDC motor

Abstract

The subject of the application is a BLDC motor dynamic braking system used, in the event of a power loss, to limit the falling speed of a rehabilitation robot arm and its method of operation. The BLDC motor dynamic braking system is characterized in that the BLDC drive controller (1) is equipped with a brake control output, which, when not braking, has the potential of the drive's supply voltage. The brake control output (2) is connected to the relay coil of the dynamic braking system (3). During normal drive operation, voltage applied to the relay coil causes the relay contacts to open, disabling braking. If the voltage at the brake control output is switched off, the dynamic braking relay contacts close, shorting the motor windings via the RH resistors. When the dynamic braking is activated, the BLDC motor (4) operates in generator mode; the higher the motor speed, the greater the braking torque generated.Braking power can be modified by using the RH resistors, which limit the short-circuit current. The RH resistors also provide protection against a transient condition following a power outage while the control module's power transistors are still operating.