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How to brake a three phase brushless DC motor?

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Hello! I'm trying to smoothly brake a three phase brushless DC motor by short circuiting the phases. At this moment an overvoltage occurs damaging the power circuit. Is this the right way to do it? Thanks
 

you do not want to short circuit the phases as you (should have) learned when you damaged the power circuits

three phase uses 6 switches
you turn them on and off in a specific pattern to operate the motor

to brake the motor, you need to change the phase pattern so that the motor acts like a generator
and send current back through the 6 switches to the source

it is akin to wiring a 3 phase motor ACB instead of ABC - it rotates backward instead of forward

please provide the schematic, including the switches, motor and control circuits
and you may get a more detailed answer
 

At this moment an overvoltage occurs damaging the power circuit.
Click to expand...

This is expected.

Plugging is considered an emergency method to stop the motor; first you disconnect the power (so that the motor runs on its own inertia) and then it acts like a generator. At that moment you short the motor terminals.

The stored energy of the motor is now dissipated into the shorted load (So you should short the motor terminals via a power resistor). Depending on the motor power (stored energy) it comes to a stop.

Regenerative braking is simpler and preferred.

You send the stored energy back to the power supply (stored in capacitors). But this may be slower.

Smooth braking may be done by reducing the speed close to zero but that may take the longest time.
 

Hi,

You say "smoothly break" .. but the you say "short circuit".
But "short circuit" is "hard breaking", not smooth breaking...

Instead of hard short circuit, you could use PWM.
Depending on your circuit this could be:
* PWM = 0: all switches are OPEN
* PWM = 1: all lower switches are ON

Then smoothly increase the duty cycle until the motor stops.

Mind: the rotating energy is pushed back as electrical energy to the bus voltage capacitors.
This means the voltage will increase! You should include some overvoltage protection.

Klaus
 

KlausST said:
Hi,

You say "smoothly break" .. but the you say "short circuit".
But "short circuit" is "hard breaking", not smooth breaking...

Instead of hard short circuit, you could use PWM.
Depending on your circuit this could be:
* PWM = 0: all switches are OPEN
* PWM = 1: all lower switches are ON

Then smoothly increase the duty cycle until the motor stops.

Mind: the rotating energy is pushed back as electrical energy to the bus voltage capacitors.
This means the voltage will increase! You should include some overvoltage protection.

Klaus
Click to expand...

I implemented the pwm and now I can smoothly break or even make a hard brake without damaging the circuit. I used the scope to monitor the voltage e adjust the pwm limits. But I just tested without load attached to the motor.
Thanks for your tips.
 

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