Dynamometer in thinking stage- VFD or DC drive

[jschwei314]

We have a motor test stand. It has an Eddy Current brake as the load. This rascal has done great for 15 years. It can test motors up to 150KW, 480volts all day and 500 KW with careful watching. The idea is to replace the brake with a DRIVE to put energy back into the system instead of making hot water.

The question, install inductor motor and regen VFD, are there any good manufactures for this? OR install DC motor and a 4 quadrant DC drive.

This will be an in-house project. The dynamometer is all manual control.

My idea is DC motor and drive for simple and proven technology. The other fella wants AC motor for the simple maintenance on the motor. Looking for VFDs that have very good regenerating capabilities. What is the experience of regen VFDs.

 

[DickDV]

Regen VFD's are not new technology and are very reliable. Pick a brand with good technical support near you and enjoy the benefits of regen AC dynomometering.

As to brands, I can personally attest to the quality of ABB, Siemens, and Allen-Bradley. There are surely several others.

 

[Skogsgurra]

It all depends.
If you are running for a few hours (functional test) then maintenance aspects are not so important. It will take many many years before you need to clean the motor or change brushes.
If you are running continuously (reliability tests) then maintenance may be an important issue.
Cost is usually lower for an induction motor than for a DC motor. On the other hand, a thyristor rectifier is a simple device that can be had for a low price. It is also fairly simple to maintain.
If you need bus communication, you will have it on all VFDs but not necesarily on second hand thyristor rectifiers.
A few points to consider. And there are others.
Re brands, I agree fully with DickDV.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[GregLocock]

In my experience with chassis and engine dynos they are DC machines, but this may be because we are using inertia simulation, which needs rapid speed and torque changes in the motor. I am not aware of any maintenance issues with them.



Cheers

Greg Locock

I rarely exceed 1.79 x 10^12 furlongs per fortnight

 

[ozmosis]

A lot depends on the dynamics of the load test you are looking to perform. The higher the dynamics the more you need to focus on the dyno drive motor and look for lower inertia rotor, then look at the drive unit to match the motor.
Another factor is how much you want to spend.
My previous company (Siemens) manufacture test stands and the equipment to go on it. We worked with a few automotive (F1) companies who were looking for high performance only. They weren't bothered about where the energy went after it had passed through the motor but the solution was found to be an asynchronous servomotor that ran of a VFD with AFE (Active Front End). The drive unit did dump the energy back into the mains via the AFE and added to the performance by maintaining a very solid DC link, even under fast dynamic load.
The motor was then a 1PH7 but I know they now have a new range of motor called 1PH8. These are motors of a similar dimension to DC motors and very low rotor inertia, ideal for fast acel/decel characteristics.
These are motors only suitable for use on Variable Frequency drives as the base frequency is typically set somewhere between 45-80Hz to achieve the optimum performance.

http://www.automation.siemens.com/mc/mc-sol/en/158de36b-5b46-4afe-b678-d7195487a95b/index.aspx

I know ABB also manufacture motors like this too and some Spanish or Portuguese company that has a name that always escapes me.

 

[fangas]

When I was working for a major motor Mfg. I got very involved in setting up an engineering / preproduction motor testing lab.

It had 4 cells. Two were wrapped around a DC based dyno and the others around AC.

The DC's were 1800 RPM machines that utilized field weakening to get to 2-pole AC speeds.

The AC's were 4-pole, with vector drives.

Both had regen.

And both were 3 times over sized their rated test limits. A stand that went to 10Hp had 30 Hp systems. This was a requirement for developing breakdown curves.

I lived with that lab for over a year. I can't put my finger on anything in particular that I liked, or didn't. But, overall, I would have liked all 4 to have been AC based.

BTW. the DC drives were an obsolete brand (The name escapes me). The AC was by Unico.

Ed

 

[DickDV]

Reliance/Baldor also makes a very good Low Rotor Inertia AC induction motor. It is branded as "RPM-AC", I believe.

I've used them more than a few times and always had good experience with them.