Gerling Laboratories Repair Facility for Motor Controllers

The line power comes into the DC rectifier. The positive output of the rectifier goes through terminal 2 to the positive terminal of the motor. The voltage passes through the motor and is returned to terminal 1. From terminal 1 it is directed to two power mosfet switches. When the switches are turned on, power returns to the negative terminal of the rectifier and power is delivered to the motor. When they are turned off, no current flows and no power is delivered to the motor. The switches are controlled by a pulse width generator. The wider the pulse, the longer the switches are on and more power is delivered to the motor. The width of the pulse is set by the power adjust potentiometer which can vary it from zero to full. Within this part of the system are feedback circuits that stabilize performance with current and voltage sensing.

Fault Detection:  The current overload system  senses the current through the motor and shuts down the controller if the current exceeds a preset level.  The shutdown causes relays which deliver power to the bridge rectifier to open.

On-board Adjustments:  There are 5 on-board adjustments.  Two of them relate to the current overload interlock system.  One controls the set point and the other sets the motor current level that will activate the system.  The other three relate the speed selection and stabilization.  Two interact with the current level.  One sets the level for the onset of control and the other sets the insertion level.   The third sets the amount of voltage feedback.