PWM controlled reversible permenent magnet DC drive

Thread Starter

sean900911

Joined Jan 28, 2013
35
Hi guys ,

Im currently doing my final year project in EE . So, my project is i m going to use PWM to control the dc motor (15V 3A) speed by using 4 quadrant operation. During the regeneration mode, I need to fix the current in 1A and this cause me trouble as well . How i am going to set the current to 1 A ? Can anyone please help me as well?
 

Thread Starter

sean900911

Joined Jan 28, 2013
35
Hi , the schematic is just a 4 quadrant operation where i only need to add an capacitor parallel to the input voltage(dc) to store electrical energy during regeneration operation(2nd quadrant) . Im still have trouble on limit the current to 1A as it store electrical energy to the capacitor as well ... Thank you so much...
 

Thread Starter

sean900911

Joined Jan 28, 2013
35
Hi, and welcome.

Can you post your schematic?
Or are we not that far along yet?


Hi , the schematic is just a 4 quadrant operation where i only need to add an capacitor parallel to the input voltage(dc) to store electrical energy during regeneration operation(2nd quadrant) . Im still have trouble on limit the current to 1A as it store electrical energy to the capacitor as well ... Thank you so much...
 

shortbus

Joined Sep 30, 2009
8,337
If you have a 3 amp motor, why do you want to limit the regen to 1 amp. It would make more sense to take full advantage of the 3 amps(less loses) available.
 

Thread Starter

sean900911

Joined Jan 28, 2013
35
If you have a 3 amp motor, why do you want to limit the regen to 1 amp. It would make more sense to take full advantage of the 3 amps(less loses) available.
Hi , Thanks for the reply...
Actually, during the regeneration operation, the kinetic energy need to charge back to the dc source and perform as generator. So, I need to parallel a capacitor operate as storage energy where it could not exceed 1A during the regeneration operation as well. This is why I face with the trouble...
Thank you very much..
 

Thread Starter

sean900911

Joined Jan 28, 2013
35
Just put a current sense resistor in the regen current path, and limit braking PWM to control the max regen current.

Hi , Thanks for the reply...
erm.. what did u mean by limit braking PWM ... Because my PWM is only using to control the motor speed as well.
 

THE_RB

Joined Feb 11, 2008
5,438
Hi , Thanks for the reply...
erm.. what did u mean by limit braking PWM ... Because my PWM is only using to control the motor speed as well.
The PWM in a h-bridge or half-bridge controls both acceleration and braking.

If the duty cycle is higher than the motor speed the motor will speed up and draw current from the battery.

If the duty cycle is less than the motor speed the motor will slow down and return current to the battery.

In both cases the PWM controls the current. To limit your braking current to 1A you use a current sense resistor in the regen current path and make sure if current is >1A you increase the PWM, this will limit braking current to 1A.
 
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