Running a 3-phase 50hz motor on single-phase 60hz power
Running a 3-phase 50hz motor on single-phase 60hz power
(OP)
I'm working on a project where I'm transforming a Honda Civic into a hybrid vehicle (where the generator will run on wood-gas) and I'm having some concerns with the electric motor's power. A Baldor 7.5 hp, 3-phase, 50 hz, 400v motor was donated to my project which I really appreciate, but it's obviously incompatible with the 6500 watt, 110v, 60 hz generator that I got prior to receiving the motor (that I plan on running on wood-gas from a gasifier). The hp is adequate (you need 6 to 8 hp per 1000Lbs of weight) and I've discovered various ways of transforming single phase power to 3-phase power (using another electric motor). I know how to step up the voltage and I read the FAQ about running a 50 hz motor on 60 hz power (FAQ237-1224: Motors: Changing between a 50 and 60Hz supply.). What I would like to know before I go to all this work creating the converter is am I trying to do too much by converting 115v single phase power to 400v 3-phase power while at the same time running it at 60hz? Will this tax the motor or generator too much?
I appreciate any advice or help you can provide.
Thank you!
I appreciate any advice or help you can provide.
Thank you!





RE: Running a 3-phase 50hz motor on single-phase 60hz power
RE: Running a 3-phase 50hz motor on single-phase 60hz power
You have two problems to solve: converting from 115V to 400V, and converting 1 phase to 3 phase.
There is no way around the 115-400V conversion, you are going to have to add a transformer somewhere. That is not only going to be expensive (compared to the donated stuff you have now), but also heavy and for vehicles, weight takes HP.
1 Phase to 3 phase is easier, but if you are already going to have to add a transformer, adding another motor to make a Rotary Phase Converter is going to add even MORE weight. You would be better off using a VFD (Variable Frequency Drive), which is capable of being fed single phase power and putting out 3 phase power. You would need to buy a 15HP VFD however, because the current through the input side of the VFD increases by the sq. rt. of 3 and the components must be capable of that higher current. But the VFD cannot create voltage that is not already there, so you still have the transformer to boost the input to the VFD to 400VAC minimum.
You might want to check on the motor to see if it is capable of being connected at a lower voltage like 230V, many are. That would help with the cost of the VFD. You will still need a transformer though, 115V is just too low to work with for anything that is going to need 3 phase. There are some VFDs you might see advertised that will take 115V input and run 230V 3 phase motors, but what they do is use what is called a "voltage doubler" board on the front-end at the DC conversion side of the VFD. That's fine, but those are limited to 1HP; nobody makes one for anything as big as 7-1/2HP. If you were an electronics wiz (or know one that likes a challenge) you could roll your own, but the parts would be expensive.
I would try for a different generator donation that puts out a higher voltage.
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RE: Running a 3-phase 50hz motor on single-phase 60hz power
Bill
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"Why not the best?"
Jimmy Carter
RE: Running a 3-phase 50hz motor on single-phase 60hz power
RE: Running a 3-phase 50hz motor on single-phase 60hz power
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Running a 3-phase 50hz motor on single-phase 60hz power
In my opinion you are wasting time and money on the project.
RE: Running a 3-phase 50hz motor on single-phase 60hz power
There was a discussion here about a week ago someone wanted to run a VFD on a battery as a backup, If I recall correctly it
would run at full torque up to a limited speed because of the V/F curve
If you were to rectify the 110 Volt would it not run to 110/400 x full speed?
Roy
RE: Running a 3-phase 50hz motor on single-phase 60hz power
1: Your generator is too small, 6500W, propably much less if it is converted to run on wood-gas.
2: Different voltages, can be overcome, but at great cost.
3: Too low power, you must have at least 20 KW.
4: AC motor is not suited to car operation, low starting torque, expensive regulation.