Testing a VFD and Motor

[Leadfoot]

Take two motors and couple them end to end. Provide the variable voltage to the input of one drive and run that drive at the input voltages you need. Run the other motor in regen. You probably will need the dynamic braking module and some large wattage resistors. Most dynamic braking resistors are for 10% duty and you will be closer to 100% duty.

YES your VFD will allow the one motor to run in regeneration. YOu have to start the drive so it provides the motor with the magnetizing currents. Then spin it backwards. The transistors do not do the work but the flyback diodes around them actually pass the energy to the bus caps. You can actually program the regen torque limits on the drives. Of course you will need to read the programming manual.

You can increase the load on the driving motor by trying to make the load motor try and turn it backwards.

Or you can get a DC regen drive and motor to act as your load and regen to the line. Another way to load a VFD is to have the AC motor run a DC motor as a generator. COnnect the armature to a large resistor bank and control the field to make the "DC generator" load the VFD and Motor to the desired load.

Your sales type that agreed to the testing needs to be instructed to have engineering proof these types of contracts prior to agreeing them.. IMO, The sales type needs to lose their commission for causing an unncessary cost.

 

[10BaseT.]

Join the DC buses together is a nice way of doing it - one drive as a torque master , the other as a follower .

And you are right , sack the salesman .

 

[agarb]

I think I found somebody to do the testing. It is actually a major motor manufacturer that has a plant 20 miles away from me. I visited them this morning. Their lab has 14 dynos ranging from 1/2 HP to 1250 HP. They said as long as I come and program the VFDs that I provide, they are happy to sell a little time in their lab. Now I just have to define a formal procedure that covers the gray areas of the specification and get my customers approval.

Leadfoot, I like your idea, but think what you described is outside my capabilities.

 

[Switchman]

If you find you really still need to dyno and can't talk your way out of it...talk to Koffler here on the left coast http://www.koffler.com/
I use them for all my 100hp and above rewinds, laser aligns, and vac blower rebuilds. They have a dyno. They are honest and fast and pricey but get it done when no one else can. They've dyno tested the dual 300hp motors I use on my ammonia compressor each time I rewind.

 

[Leadfoot]

I think I found somebody to do the testing. It is actually a major motor manufacturer that has a plant 20 miles away from me. I visited them this morning. Their lab has 14 dynos ranging from 1/2 HP to 1250 HP. They said as long as I come and program the VFDs that I provide, they are happy to sell a little time in their lab. Now I just have to define a formal procedure that covers the gray areas of the specification and get my customers approval.

Leadfoot, I like your idea, but think what you described is outside my capabilities.

Glad to see you found a dyno. After you have done the actual testing, you will see what I was describing. The dyno guys will be able to add some details on how things actually work.

Then you will be better qualified to build your own.

10baseT, the common bus won't work as the input voltage must be varied as part of the test and the load drive needs a steady voltage to run with out issues.