Braking Resistor

I

itrade

Joined
Jul 3, 2002
Messages
645
OK I have a permanent magnet DC motor and a DC controller. I didn't pay the bucks for one with a brake. I figured I can wait for it to slow.

Thinking again I thought it would be easy to have a switch that disconnected the motor from the line and connected it to a resistor so slow it down. No big deal. It's covered in the connection manual as a possible setup.

However I don't know the amount of resistance to use.

Here's what I do know:

90vdc
14amps
3600rpm

Looks to me like I need about a 1500 watt resistor. But how many ohms?

Anybody have a similar sized DC controller with a brake? Can you look to see the size of the resistor (if that's what it uses).

Steve
 
Are you talking about slowing it down with electrical resistance and actually grinding that way?


EDIT: If you want to get the RPM down to about half I may be able to help you with a value but you will have to determine the resistance of the motor winding first.

Roger
 
Steve, not really sure what you are trying to accomplish, but I have used stove elements as braking resistors for AC Varible Speed Drives many times.Much cheaper,but have not tried it on a DC unit.Braking resistors can get a little pricey and need some sort of ventilated enclosure.Dave:)
 
Thanks Guys,

Dave: stove element is a great idea. The braking resistor idea is just to help the slowdown/stop process when the controller is turned off.

I surfed around and found a controller site with a 'rule of thumb' table. Looks like a 40 ohm/50 watt resistor will do just fine.

I also found an easy forward/stop/reverse diagram using a 3 poll/3 throw switch.

Thanks again for the help!

Steve
 
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