vfd WITH INDUCTION MOTOR AS Dyno

[Far12312]

Hey, I am making my own dynamometer setup, and I bought a 3-phase VFD (2.2 kW) for a 3-phase 2.2 kW induction motor. I will use a torque transducer between the induction motor (load) and the test motor (DC motor, 2 kW). I set the VFD to torque control mode with minimum and maximum values, and I will use a braking resistor as well. Can anybody give me any suggestions on whether I should set the minimum value to 0 or 50% of the motor-rated torque, or any ideas on how I should control the torque?

 

[LionelHutz]

I'd control the torque by measuring it and then using a PID to change the frequency to get the torque you want. The trick is getting the VFD initially operating at the speed you want it to. It'd probably require 2 measurements, speed and torque and use both to set the operating frequency.

 

[waross]

What is driving the motor?
Will the driving speed be steady or variable?
What information do you want at the end of the day?

 

[Far12312]

so the driving motor is permanent magnet dc motor havng 1500 rpm 2 kw and i want to run it on full load which is 3.54 nm for 30 mins but the speed would be 1500 rpm maxmum and the induction motor which i will try to use as load has maximum speed 2875 and my only query is when i set vfd on torque control mode setting the toque max 100% and torque minimum 0% and when i try toset only torque the speed of the induction motor alose increase where as it should be run by only driving motor what do you suggest should i give torque min 3.54 and the drive that with my driving motor?

 

[waross]

maximum speed 2875

Maximum speed or full load speed.
It will probably run very close to 3000RPM at no load.
If the same frame is used on 60 Hz the no load speed will approach 3600 RPM.

 

[Far12312]

1500 rm is no load speed since its pm dc motor with full load the value goues to 1448 or 1450

 

[LionelHutz]

What'd you set the speed to? You need the VFD to be trying to run at a lower set speed but torque limiting so it lets the motor run over speed. Then, as you increase the torque limit the VFD will try harder to pull the motor down to the set speed.

 

[Far12312]

Thank you for your I was thinking the same I even ordered a seprate braking resistor but intially i will try this on lower speed..