50hz motor run in 60hz environment
50hz motor run in 60hz environment
(OP)
I have a problem that I hope someone can help me with quickly.
We are using a 100 hp 380v/3ph/50hz motor in a pedestal boom that we produce. We need to test this boom/motor combination in house. How can we test this assembly in house where we have 460/3/60hz supply. We need to simulate end user conditions (380/3/50hz). How can we do this? This is a direct drive situation which is powering the hydraulic circuit of the boom.
Ken
We are using a 100 hp 380v/3ph/50hz motor in a pedestal boom that we produce. We need to test this boom/motor combination in house. How can we test this assembly in house where we have 460/3/60hz supply. We need to simulate end user conditions (380/3/50hz). How can we do this? This is a direct drive situation which is powering the hydraulic circuit of the boom.
Ken





RE: 50hz motor run in 60hz environment
The problem you may have is: can the driven equipment can be safely run at 60HZ speed. You can estimate this load by multiplying measured load current at 460 Volts by 1.25.
You may run at high overload, up to breakdown, for short periods. If you need determine the time period, place a thermocouple on the windings and measure the temperature. To be safe, shut down at 105 degreeC total. If you can't access the winding, place the tc on the iron core and drop the same temp to 95 degreeC.
RE: 50hz motor run in 60hz environment
Mike Bensema
www.dutchmenservices.com
RE: 50hz motor run in 60hz environment
You may consider renting a generator set if you just need a short term test.
I don’t know the area you’re in, but I did a MSN search for:
“caterpillar generator rentals”
and had a list all over the USA.
David
RE: 50hz motor run in 60hz environment
Thanks for your responses.
I will be looking into the potential of purchasing a VFD but with the economy the way it is we will probably rent a generator to help us for now. This situation appears about once every year or two so I don't know if I can justify the purchase of a VFD but I will try.
Thanks again for the responses.
Ken
RE: 50hz motor run in 60hz environment
I really don't know much if anything about VFD's but I am trying to learn as much as I can, as fast as I can.
Thanks
Ken
RE: 50hz motor run in 60hz environment
The other option is a motor/generator set; 460V 60Hz motor, and a 380V 50Hz generator.
RE: 50hz motor run in 60hz environment
For programming of the VFD, you would enter the motor parameters of 380v 50 hz, motor speed, FLC, etc. and then the VFD will adjust the voltage and frequency in the proper ratio. So when running at 50 hz, it will output 380 v. If you had a different motor that runs on a different voltage at that frequency, or another frequency, you can program it to run that way too. The VFD is very flexible that way.
If you ran into problems with your machine and wanted to run the motor slower to test something, you could easily do that with the VFD. Once it's programmed, you could adjust the running speed anywhere from the minimum to maximum speeds the motor or pump could safely run at. The VFD will then adjust the voltage and frequency to maintain the ratio that was programmed in from the nameplate settings.
Feel free to let me know if you have any more questions.
Mike Bensema
www.dutchmenservices.com
RE: 50hz motor run in 60hz environment
"I really don't know much if anything about {...} but I am trying to learn as much as I can, as fast as I can."
Aren't we all? Please be very careful about using the web as a sole resource for one’s understanding.
RE: 50hz motor run in 60hz environment
Just $0.02 worth on the side of caution.
RE: 50hz motor run in 60hz environment
RE: 50hz motor run in 60hz environment
RE: 50hz motor run in 60hz environment
RE: 50hz motor run in 60hz environment
One more question about a VSD.
Assume the VSD is running at 50 hertz and 0 load then you hit it with a D-O-L starter and 100 HP motor connected. Would you expect the inverter to survive this type abuse for very many starts?
I would think the drive would not be very happy in this type operation. Would there be any expected problems doing this?
David
RE: 50hz motor run in 60hz environment
Mike Bensema
www.dutchmenservices.com
RE: 50hz motor run in 60hz environment
I may have read more into the original question than was there. What I see implies that they want to test the electrical and/or possible hydraulic operation of the boom and controls. I would think that this would include a test for a motor starter of some type to operate the 100 HP motor.
Maybe I don’t understand the test, but that is why I was confused about all the VFD answers. It would seem that a gen set is the only real choice.
David
RE: 50hz motor run in 60hz environment
RE: 50hz motor run in 60hz environment
I'm not trying to ask stupid quistions. I just don't know.
Most drives have a reverse on the fly option. Reverse on the fly ramps down then back up.
Does reverse on the fly mean that you can close a D-O-L starter on the output of a not loaded VSD?
David
RE: 50hz motor run in 60hz environment
RE: 50hz motor run in 60hz environment
Once again I apoligize, but I don't understand. Does this mean that some drives can take a D-O-L start on the secondary?
David
RE: 50hz motor run in 60hz environment
I have not come across any drives that can reliably run a motor starter on the output, but there certainly could be some if one was willing to pay the premium. I had a paper on the problems associated with that and can't find it now, but the reason for not using a starter on the output is the sudden current inrush to the motor overloads the IGBTs and they fry. If you specified components that could handle the inrush, then it should be possible to do as jbartos mentioned, but for people with budgets lower then the Navy, it's probably not practical and why you don't see them.
Mike Bensema
www.dutchmenservices.com
RE: 50hz motor run in 60hz environment
What about all those motors that are of a plugging type? These would not be suitable for VFDs or a special VFD would have to be developed.
RE: 50hz motor run in 60hz environment
http://www.control.com/1026161072/index_html
for more info.
The VFD can have current regulators on its output that prevent the switching devices from being damaged.
RE: 50hz motor run in 60hz environment
Maybe I am missing something, but it works for us.
RE: 50hz motor run in 60hz environment
#1 - Will the mechanical load work properly at higher speed.
#2 - Is there a speed-dependent resonance at the lower speed which doesn't show up testing at higher speed? How do we know that equipment will meet vib limits at the lower speed if we haven't tested it?
RE: 50hz motor run in 60hz environment
The VFD & generator ideas both sound good to me. Another idea: motor-generator set or other power converter.
My understanding is VFD's generally work as current sources, so they should generally never have their output open-circuited. I could be wrong, but I'd definitely check with the manufacturer before you tried to put a downstream starter. I've seen various installations where downstream safety switches are interlocked with the VFD to prevent open circuiting.
Whatever solution you come up with, be aware that you need to account not only for full-load current, but also starting current of your motor. This can imply substandtial derating of your generator/VFD/converter/etc; that is, you might need a 200hp/kW/kVA-rated source (or bigger) to properly start your motor.
RE: 50hz motor run in 60hz environment
Bottom line is that it will function flawlessly at 460 in your application.
RE: 50hz motor run in 60hz environment
If he drives his hydraulics at 60Hz, the bhp will increase, possibly to the point of overloading the motor. Yes, if the motor works at 60Hz, it should work at 50Hz. But this could be overconservative: the motor could fail at 60Hz but still work at 50Hz.
Am I missing something here?
RE: 50hz motor run in 60hz environment
Running hydraulics or an oil pump at a higher speed will pump more through the system. Take an oil pumping unit supplying oil to the machines bearings. At 60 hz you are pumping 20% more and can easily hide an overheating bearing or a design problem that does not supply enough oil at the rated speed. It's cheaper to find a problem on the test stand then it is at the customers site.
Mike Bensema
www.dutchmenservices.com
RE: 50hz motor run in 60hz environment