Measuring Torque on DC motor

[Fullelove]

How would I measure the maximum Torque available on a skip winder DC motor over its speed range. What characteristics of the motor parameters etc would I need to know and how wold I test the Torque. The is a in service motor and not in a lab. The skip can loaded fairly exactly for purpose of testing if needed. The Drive is thyristor converter type.

Really appreciate this.

 

[cbarn24050]

Hi, its quite easy to measure. On the drive unit you will find a current limit control, make a note of where its set. Load up your hoist with a known load about 25% of what you expect your hoist should lift. Turn the current control to zero, start the hoist, then slowly turn up the current limit untill the hoist just lifts the load. measure the armature current.Switch off reset the control to its normal setting.Read the motor flc from the nameplate. Torque is proportional to current so (measured current/flc) = (test load/max load).

 

[Fullelove]

That would seem to give me starting torque but will this give me maximum torque over the full speed range?

 

[skills]

If current is constant, the torque is constant. A dc motor that is current regulated has torque Tau=KI*I or something like that so the answer given by cbarn seems to be pretty good. I believe that voltage constant and torque constant is also the same for dc machinery. Also, in response to your above question making a distinction between maximum torque and starting torque, I would think them to be the same since that is why they continue to be used in many applications. A dc motor can make full speed torque @ 0 rpm.