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DC breaking injection

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abc_de

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DC breaking injection for 3 phase induction motor

Hello
I am working on 3 phase AC induction motor control.
Presently I am trying to implement DC break Injection.
I did an experiment I had apply 24 v DC to induction motor without apply 3 phase then shaft of motor become jam(difficult to rotate with hand)
But I don't know how I can implement like maximum DC voltage ,ampere, maximum time etc. Without damage motor.
Thanks
 
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KlausST

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Hi,

No schematic, hard to help.

We don't know how your motor control works. Maybe pwm from high voltage.
To break you could use a low duty cycle pwm on one phase, while ( at least) one other is 0% duty cycle (always low).
There are many other possible solutions.

Klaus
 
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abc_de

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I am using pic18f4431 microcontroller,IR2110 as gate driver, FGA25N120 IGBT
ACIM motor is control by 3 half bridge of IGBT.
I got your point by low pwm duty cycle of high side igbt and another leg permanent turn on lower IGBT will give DC voltage according to the duty cycle of pwm.
But want to know to break 1 HP ACIM how much DC we can apply and how long we have to apply
 
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KlausST

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Hi,

But want to know to break 1 HP ACIM how much DC we can apply and how long we have to apply
Max duty cycle.
Max current (given for the motor) x R_dc givs max_voltage.

Duty cycle = max_voltage / rail_voltage (half bridge supply voltage)

*****
How long: as long as motor moves. Try it, maybe add a second or two.

Klaus
 

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Why don't you review the user manuals of industrial VFD inverters about the implementation details of DC breaking?

Some questions have to be answered by yourself. "How long" refers to the moment of inertia present in your system. We can't know it. Applying up to twofold rated current for a number of seconds won't damage the motor.
 
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