Q: I'm using an AR98AK-N25-3 package model which includes the AR series geared stepper motor and a dedicated pulse input type driver. I noticed that the RGB100 regeneration unit is only offered for the AC input systems; not for DC-input systems like mine. Why is this? I also need to know the exact conditions inwhich I should use a regeneration unit. Do you have any more specific information?
A: When a conductor is moved through lines of magnetic flux, current is induced onto the conductor thus generating current. When a motor is back-driven by external power, this theory applies, and the motor actually becomes a power generator. If enough regenerative power is generated and it exceeds the rated value of the driver's components, damage may occur.
Since the AR series motors are much more power efficient than other motors, it actually generates more regenerative power. There is nothing to worry about since the AR series driver will generate an overvoltage alarm if it senses an increase in back EMF from the motor, and it will stop operation to prevent damage to the driver's components.
A regeneration unit such as the RGB100 (50W, 150 ohms) or RGB200 (200W, 50 ohms) is recommended when you are:
-direct-driving a load in the vertical direction,
-driving a large inertial load, or
-starting or stopping the motor abruptly.
These are the instances where regenerative power could be generated by the motor, and it needs to be dissipated with the regeneration unit. It also does depends on other factors such as inertia mismatch ratio (between load inertia to rotor inertia) and speed. AR motors using a linear actuator most likely won't need a regen unit even if it's vertical.
Please refer to the following chart for reference only:
As long as you have a 1.5:1 safety factor for required torque on your motor, stay within the top speeds, and also stay within the inertia ratio for your particular AR model, you most likely do not need a regen unit.
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