Making 400V 3-phase 50Hz in USA

[megloff11x]

We're looking to sell in Europe and need to set up testing for 400V 3-phase at 50Hz for up to 250A. Back when my work was lab instruments at another job, we paid a new car price for a device that generated 80-264V, 40-80Hz, and I think up to 20A, for testing out small instruments (wall outlet power). It was the size of a computer tower.

We had enough problems with the 50Hz issue - brownout detect circuits tripping because 50Hz allowed more sag, loss of compliance Voltage over the extra 16% time between peaks - the canned calculations for capacitor size didn't allow enough margin. Problems in Japan (100V nominal and serious power quality issues), small transformers rated for 50Hz that really wouldn't work at that frequency and would just draw >10x their 60Hz rated current until the fuse blew or they melted, etc. We thought it prudent to test under as close to actual conditions as we could make. We had these and enough other unexpected problems that we bought the device and learned not to flaunt Murphy's laws. And we learned a lot of interesting little things we never expected would happen.

For huge scale industrial machinery, what's the way? The easiest may be a 208 or 480V to 400V transformer, but you are still at 60Hz. If you think frequency won't cause problems, that may be the least expensive.

The only other way I can think of that would be cost effective at these high current loads is to use a generator and run it slower to make 50Hz power. I would think that a PWM system might have too many noise issues and cost too much, but the prices & power quality may have improved.

Has anyone set something up like this at an industrial machine manufacturer, and can you elaborate?

 

[wirestripper]

"The only other way I can think of that would be cost effective at these high current loads is to use a generator and run it slower to make 50Hz power. I would think that a PWM system might have too many noise issues and cost too much, but the prices & power quality may have improved."

I think you answered your own question. On a small scale, you can do this electronically, but to run anything over 10 or 15 A, you need to use a tricked out generator and will be changing all sorts of things from the governor to the power regulators and the like.

Good luck!


PS, I worked for years with German equipment that was marketed in the U.S. and in Europe. They were electric tower cranes.

I would consult with a German firm on this, and perhaps one of their brilliant engineers could help you. But they like to be paid. They shipped a protype portable crane to us once that required only to set up a autotransformer and adjust the output until we were in the ball park. It worked just fine, and frequency affected only the motor speeds which were adjustable via motor controllers and the like. Everything else worked just fine. Just refrain from sychronous cooling fans, or build in plenty of overkill.

 

[winnie]

I've worked with PWM at these power levels, and with somewhat smaller motors. But I've never had to operate a generator at 200kW and get the output 'right'. I've not had to work with the sort of conversion that you are describing, and might be missing something obvious.

I'd first suggest that you consider 'renting', eg. working in a facility such as http://eecs.oregonstate.edu/msrf/

PWM based systems can certainly reach these power levels; you are basically talking about an inverter capable of running a 250-300hp motor. But the output won't be particularly clean; these inverter based drives operate at a switching frequency of a couple of kHz at most, and if you use them to supply something other than a very large inductive load (motor) then you would get a rather ugly mess.

My best guess is that you would be best served using a motor generator set. Systems that simply convert 60Hz to 50Hz are common enough that companies advertise these systems on the web, eg http://www.hzfrequencyconverter.com/60Hzto50Hz.html or http://www.50hz.com/Rotary/rotary.htm I used the search phrase "50Hz 60Hz motor generator set" in google.

You might consider using a system with a VSD inverter on the drive motor of a motor-generator set, with manual control of the output voltage. Rather than nice pure 50Hz, you would then be able to synthesize 50Hz +- some variation in voltage and frequency.

I'd love to hear of what sort of system that you eventually install.

-Jon

 

[ramsy]

In Febuary, while working the NAAM music trade show in Anaheim, CA, I installed a 120v 60Hz primary to 230v 50Hz sencondary boost transformer for a European sound & music equipment booth, from England. This shobox size xfmr was spec.'d by the equipment Mfg., and provided by the client at the booth. However, since, it was fed from a 20A ckt, it couldn't have provided much amps.

There were other booths using larger boost xfmrs., especially at the next show, were I saw large MRI scanners & other medical instruments from German Mfg's., but there were others. If larger 50Hz boost xfmrs are not available domestically, perhaps you can find them internationally on line?

 

[c-h]

One question is if you need to test deviations from the nominal voltage. It is probably easier to design a power source that gives only 50 Hz, 230V +/- 0% than to find something that can adjust the voltage +/-10%.

Winnie's idea is interesting: Maybe you can user a motor generator set and drive the motor from a variable frequency drive (inverter) configured for 50 Hz output. (With 60 Hz input, of course) That gives it a common shaft (no gears) and should filter out the high frequency noise from the inverter.

Maybe the following product is something like that:

http://www.pscpower.com/pages/rotary_frequency_converter.htm

 

[barclayd]

Contact Piller Power Systems http://www.piller.com/
They make various sizes and configurations of Frequency Converters.
They will give you 'orders of magnitude' better service than anything you could possibly cobble together.