3 phase dynamic breakibg

That's about what I expected the answer to be.

Many years ago a company I did some work for made up a cheap and dirty DCIB for some 480 volt conveyor motors by connecting two capacitors to two motor legs through a bridge rectifier and connecting the other side of the cap to the 3rd leg. This charged the caps to about 600 volts when the motor ran. A two pole relay in parallel with the bridge connected those two legs when the motor contactor shut off to discharge the caps. It wasn't elegant but it did work.

sound a nice idea. Just not sure how much braking power is obtained by uf lol ..Btw when an AC cap is installed directly parallèle to a motor after a motor contactor it would probably do the same at a certain point...when AC line open, the cap remain charged at it's last waveform state and discharge into the motor under a DC curent form....
I will make a test with a no load motor just for fun if it stop faster connected to a cap or not...
 
I would advise against testing the capacitor system described. A UL listed DC injection brake is your best bet.

It is true that braking heat is directed to the rotor but the motor is spinning for much of its decal time so the cooling fan should be doing its job keeping the rotor temp under control. The fan clearly would be less effective at the lowest speeds but then the braking kw is dropping fast.

In addition to Motortronics, Benshaw and ABB also make stand-alone DC brakes.

The BIG benefit with DC braking is the lack of wear elements compared to a mechanical brake. The BIG disadvantage of DC braking is its inability to hold the load stationary after stopping.
 
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Plugging a motor used to be practical on the old standard efficient motors but don't even think about it on high efficient or premium efficient motors. The inrush currents would be astronomical and a broken shaft is a distinct possibility
 
... In addition to Motortronics, Benshaw and ABB also make stand-alone DC brakes. ...
The ABB one is a brand-labeled Motortronics, but may be more accessible through ABB depending on where you are.

The Benshaw, Solcon and Ambitech brakes are all not CSA or cUL listed, which can become problematic in Canada (and some areas of the US). The Motortronics/ABB is cUL listed, which is acceptable in Canada. It's the only DCIB I am aware of that is listed by anyone for North America.
 

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