The efficient Dyno

[BrianHG]

A large 24V alternator with modified control will do the trick. Given the not terrific efficiency a 1KW output alternator will be fine as it will be at least 1.5KW in mechanical power and the input to the motor controller is at most 1.2KW and then you have the looses in the controller and the motor.

Yes, that should work.  Remember car alternators are specified at engine RPM, not their RPM.  The engine has a larger pulley than the alternators gearing up the alternators RPM compared to the engine value.

Stripping out the alternators internal electronics, or at least taping the 3 phase coils directly might help in your situation.
Modern alternators already use switching supplies to downconvert to 12v.
A 24v regulated output truck alternator, with 'self internal excitation circuitry' may be perfect for you off the shelf, no mods at all.  Just a GND and +24v output on the thing.


Something like this: https://www.amazon.com/ALTERNATOR-DELCO-ENERGIZING-HOOKUP-SE24Vv/dp/B004SOZK86/ref=pd_cp_263_1?_encoding=UTF8&pd_rd_i=B004SOZK86&pd_rd_r=JHQKM0427T3RZEWME0V5&pd_rd_w=VZSs7&pd_rd_wg=Zi6LM&psc=1&refRID=JHQKM0427T3RZEWME0V5

[Simon]

A large 24V alternator with modified control will do the trick. Given the not terrific efficiency a 1KW output alternator will be fine as it will be at least 1.5KW in mechanical power and the input to the motor controller is at most 1.2KW and then you have the looses in the controller and the motor.

Yes, that should work.  Remember car alternators are specified at engine RPM, not their RPM.  The engine has a larger pulley than the alternators gearing up the alternators RPM compared to the engine value.

The motors run up to 12'000 rpm

[joeqsmith]

Not sure I can be of much help but I did design a little toy dyno some time back to sort out the controls for a larger one.   I started out with a brush DC motor for an absorber.   I was using some old VCR recorder and a few toy hobby motors that a friend of mine had given me to simulate the DUT.   These would run over 12,000 RPM.   

The system can run constant torque while sweeping the RPM or constant RPM while sweeping the torque.   We never supported all these features with the actual dyno.  The large one is water cooled.   

Just to be clear, I don't own and have never owned any toys that use these motors.  This was just a proof of concept was all.   

Link showing the build. 
https://www.msuk-forum.co.uk/forums/topic/81512-self-built-rc-dyno/?page=6