AC dynanamometer control loop?

[jlcortex]

Hello,

I am planning to build a dynamometer like this one, i have experience with dynamometers, we have make software for engine test dynamomemters with eddy current brakes but never with AC asynchronous motors.

I know i need a vector control VFD, not v-f VFD, but my question is about how to control this dynamometer:

- Do we have to run a PID externaly to VFD unit? and then out controller gives target torque to VFD.
- or Do we have to gives directly target RPM and VFD have an internal speed PID?

Any requirement about control loop speed or any vector VFD would works?

I have very little experience setting VFD.
Any information is welcome, thanks
jlcortex

 

[sreid]

You need to run the VFD in Torque Mode (or Current Mode). The motor torque will be proportional to the VFD current command input.

 

[itsmoked]

I'm not so sure you need vector as you're not trying to hold some position or position relationship.

Notice the heater for dumping the power? If you get a regenerative drive the power can be fed back into the power grid without needing resistor banks or roasting your workspace. It also gives more use for the power connection you need to supply anyway so the drive is awake when it starts getting driven.

I certainly hope you protectively mount the drive on something so it isn't idiotically laying on the floor as depicted above.

You should confirm the drive you contemplate can "catch" a load. That means it is capable of engaging smoothly with an already spinning motor, not all drives can do that.

You'd probably want a drive that offers torque control.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[sreid]

Another simple possibility is DC injection Braking.

http://en.wikipedia.org/wiki/DC_injection_braking