Baldor Dynamic Brake - How does it work ?
Table saw came with Baldor Dynamic Brake, model BQ7-030-CP. Haven't hooked it up yet...probably works fine...but in the meantime just curious how it actually works and if anyone has any experience getting manuals for things like this from Baldor ? I probably don't actually need a manual for it, as the wires are all marked nicely from previous disconnection.....but would be nice to have.
(see last two pages)
Found the manual online !
When you try to electrically slow down a motor faster than it would coast down on its own, the motor will basically turn into a generator and pump energy back into the VFD. This will cause the VFD's DC bus voltage to rise, which in turn will cause the VFD to trip out on a High DC Voltage fault. Once that happens the VFD loses control of the motor and it will simply coast to a stop.
Dynamic Braking adds a resistor and transistor (switch) across the DC bus. When the DC bus voltage rises to a certain level (lower than the trip level but higher than the normal level), the switch will close and the excess energy will be routed through the resistor and rejected as heat. Once the voltage drops back down the switch opens again. This cycle is repeated over and over, allowing the VFD to maintain control of the motor in order to decelerate it much faster.