I'm developing a BLDC driver, which will provide up to 200W at a maximum of 7A. Now I'm not sure if i really need a braking chopper included, because the power is actually quite low, but ofc when a large load is spinned up to a large velocity, a big amount of energy will be stored. But when I now power the motor controller the whole time, for example with a velocity controller, the power will be used to reduce the stored energy without the need of a braking chopper, right? So my question is, when (for what application/control mode) is it really necessery to include a braking chopper and when can I just let the controller reverse power the motor to decelerate?
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asked Sep 21, 2018 at 7:16
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\$\begingroup\$ Then the reverse power bridge burns out from twice the surge current from twice to voltage when you include BEMF. Either add mechanical brakes or use an e-brake (with chopper) \$\endgroup\$– D.A.S.Commented Sep 21, 2018 at 7:34
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for example with a velocity controller, the power will be used to reduce the stored energy
No, the power will not be used but rather recuperated. The voltage on DC link caps will rise. As long you can decelerate the load without exceeding the max. voltage of DC link components, then you don't need a chopper.
You can also increase the capacitance, increase the ramp time when decelerating or simply put a bridge in Hi-Z, like disconnecting the motor and free spin the motor until it stops.
answered Sep 21, 2018 at 7:48
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\$\begingroup\$ Ok, so for safty reasons its a good idea then. Can I also just take a high power mosfet and short the DC link at too high voltage without a power resistor, since space is crucial here. This way the energy will be dissipated in the motor windings, right? \$\endgroup\$ Commented Sep 21, 2018 at 8:01
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\$\begingroup\$ @HansPeterLoft Of course, not. This will make a short on a DC link, blowing the MOSFET immediately. \$\endgroup\$ Commented Sep 21, 2018 at 8:20
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\$\begingroup\$ Ye ofc, don't know what I tought here. What makes me suspicious about current choppping at all is, that only a few BLDC motor controller on the market has this method integrated. If you use a battery, then you dont need that, but with a power supply it would destroy most probably the controller, right? \$\endgroup\$ Commented Sep 21, 2018 at 17:10
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\$\begingroup\$ @HansPeterLoft You did not mention about the battery, your application, ...how can we know? \$\endgroup\$ Commented Sep 21, 2018 at 17:56