breaking resistor

[buck33k]

I saw a breaking resistor mounted in an enclosure on the exterior of a motor control center. There are three identical sections to it, each having a wire wound around a ceramic center and each section appears to be wired in series with the other.

What is the purpose of the breaking resistor and is its function applied to all motors in the MCC?

thanks
Buck

 

[rattus]

Re: breaking resistor

Buck, do you mean "braking"? Sounds like dynamic braking which is sometimes used on DC motors or synchronous motors. I must admit though that I am guessing.

 

[buck33k]

Re: breaking resistor

Rattus
Thanks for the responce. I'm not sure of the correct spelling, it could very well be "braking".
It looks like a space heater at first glance with its coils and general appearence. The enclosure is well ventilated allowing a clear view of the wound coils.
Buck

 

[buck33k]

Re: breaking resistor

Rattus
You were right. Now knowing the correct spelling I found my answer. Apparently the braking resistor is used to absorb energy from a freewheeling motor and release it as heat. Many thanks.
Buck

 

[mdshunk]

Re: breaking resistor

Yes, some braking resistor assemblies are so large and generate so much heat that they have cooling fans or chiller lines run through them.

 

[kiloamp7]

Re: breaking resistor

Could they be resistors for closed-transition type wye-delta starters in the MCC?

Or for primary resistor type starters in the MCC?

 

[buck33k]

Re: breaking resistor

There is one variable frequency drive in the MCC. I assume the braking resistor is associated with this.

 

[rattus]

Re: breaking resistor

In ancient times streetcars used dynamic braking to pump energy back into the trolley lines. Nowadays hybrid autos use it to pump energy back into the battery.

 

[petersonra]

Re: breaking resistor

Originally posted by buck33k:
There is one variable frequency drive in the MCC. I assume the braking resistor is associated with this.

sometimes motors experience regeneration - they actually absorb energy from the load and convert it to electricity. this has to go someplace and a brake resistor is a common arrangment for beleeding this energy off.

Examples of these type of systems: loads that have some vertical component (i.e.-are getting "help" from gravity in one direction) or loads that have to decelerate faster than friction can bleed off the kinetic energy stored in the system.