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# understand a dynamical braking system

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#### electricboy

##### Newbie level 6
Hi,

I finally found a way to brake dynamically a drill and i found it on a circular saw.
I've drawn the electrical scheme of its brake which work with the drill (both the coils and the rotor are the universal motor).
The problem is that I want to resize the componant to make it brake faster.But I dont fully understand of this brake work.

Can anybody enlight me?

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I am not able to read your diagram very well. To brake a universal motor, there are two ways, one is to inject low voltage DC into the motor*, the other is to put a low value resistor (or a short) across the motor. I think your is the first type.
* typically 230V ac motor has 12V DC braking (same current or you burn out the windings).
Frank

When you close the switch the number 3 and 4 are connected then the current flows in the coil 2 and it works.And when the switch is open again, 3 and 4 disconnected, that cut the current and the 2.2µF capacitor put his current in the motor by the brush 2.

The problem is that I don't understand the midle part of the circuit why is there a Mosfet with the capacitor and a thyristor? And why they made a rectifier (if I not wrong) in both the part of the circuit?

I doubt, that the circuit is correct (respectively complete). The capacitor will prevent an armature DC current, thus I can't see a braking action.

Hi FvM,
And if the polarity of the capacitor is inversed (because i'm not sure of his sens) would you see a braking action?
this diagram is the circuit that I have verify a couple of times so i Think that everythings is there and when
I tried a lot of time there 's really a braking action (instead of 4 or 5 sec the motor takes 1 to 2 sec to brake with it.)
But the assumption with the current flow may be wrong ...

---------- Post added at 11:30 ---------- Previous post was at 10:17 ----------

Sorry I just have found that the capacitor in derivation with the diodes are varistors

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