DC Motor Test Help

[deadnotem]

Hello friends;
I must prove that our DC motor (1.2kW @ 6000rpm) provides the needed torque depends on the rotational speed. For this reason; a torque should be applied by another DC or AC motor, while measuring the rotational torque.
Firstly, in this application should I use AC or DC motor?
Could I use servo motor+driver? (I think there occurs an error in driver, even so I want to ask...)
Could a brake motor operate while accelerating?

Thanks for replies...

 

[ScottyUK]

You could use either an AC or DC machine to load the motor under test. Either way you need somewhere to dump 1.2kW of regenerated power: with an AC machine that would easiest using a regenerative drive; with a DC machine you could use either a regenerative controller or a resistive load bank.

It would make more economic sense to take your motor to a motor test shop and use their dynamometer.


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If we learn from our mistakes I'm getting a great education!

 

[waross]

Prony brake?

USE AT YOUR OWN RISK!!

http://my.voyager.net/~jrrandall/PronyBrake/PronyBrake.html

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

I've seen something not dissimilar rigged from a truck brake. Air pressure was applied to release it, and the pressure bled down until the desired load was achieved. It ran blistering hot, even when water was dribbled on it. From memory it was good for about 50 HP or so when 'liquid cooled', if that's the correct term. I suspect any British patent was likely held by Messrs Heath and Robinson, although US rights might have been acquired by a Mr. R. Goldberg.




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If we learn from our mistakes I'm getting a great education!

 

[waross]

I believe the European standard for truck brakes is spring applied, air released.
The North American standard is Air applied, spring released.
Scotty's suggestion is valid, but if the brake you find is North American pattern, just go with it.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[deadnotem]

Actually I'd like to try the methods you have mentioned.
But I should measure the torque simultaneously and certificate the results. Could I adjust the load torque for this brake system with 2 or 3Nm precision?
Also I've searched for some dynamometer test stands as ScottyUK told. I've found magtrol dynamometers. It exceeds the load torque need for the system, but motor could handle this torque. So I could prove that motor power is adequate.
Secondly a torque measurement system, and a physical brake system as you mentioned (truck brake etc.) can be considered. But in this case I should convert this system to a close loop system. It will take more and more time. And time is limited.
What do you think, which method is suitable?

 

[DickDV]

Why not use an ordinary three phase AC induction motor and do DC injection braking? Once you calibrate the NM/amp value of the system, you've got a low maintenance, low cost, adjustable system.

 

[ScottyUK]

That's a nice idea Dick. Just need something to calibrate it against!


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If we learn from our mistakes I'm getting a great education!

 

[JohnWaa]

Back in the 80's LoveJoy (the coupling people) branched off into the drive business.

For testing and burning in their drives, they used two AC motors, one 1800 RPM and the other 1200 RPM coupled together to provide a load for the AC drive (the drive was connected to the 1800 RPM motor).

This provided a load for the drive and regenerated some of the otherwise wasted energy back into the system. It worked very well. 6000 RPM might be a bit tricky though...

As for measuring your load, the Autogard folks make a coupling that transmits its torque to a receiver.

http://www.autogard.com/uk/products/tmonitoring/monitorq/page1.htm

Or just buy a small Eddy Current Dynamometer.