The BEMF on a DC motor is what restricts the speed for a given input voltage. IOW, if you you apply a certain voltage to the motor, the motor will increase speed until the BEMF voltage is equal (or slightly less) than the applied voltage.
If you are using a 160 v motor, then if this motor were to be rotated at its rated rpm, the output would be 160vdc.
If you are using it in an application where the speed is not being controlled, i.e. no feedback, then the amount of BEMF is unpredictable, and will depend on what effect the back feeding will have on the rpm.
A couple of options is either to use a controller that takes tach feed back, (requires a tach on the motor).
Use dynamic braking, this is usually a braking resistor switched in by a HexFet or similar device, when the detected voltage reaches a certain point.
Another method is to reduce the voltage to the motor when descending, or simply switch a resistor in parallel to the motor when descending also.
The value may have to be arrived at by trial and error.
Al.
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CNC, Mechatronics Integration and Machine Design.
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E. |