Demand metering is typically only allowed for the commercial rate tariffs. I'm also about 1 mile from a regulator bank. The utility here is pretty good actually, one day those regulators went out of whack and gave me 136/272V. I called the utility and got a call back from a tech in the area within 10 min, and in another 10 min he was parked in my driveway and on the radio to another tech heading to the regulators. Problem resolved in less than 30 min from my call.
Not impossible but you would have to know a lot about the detail design of the drive and be prepared for a lot of messing about with the printed circuit board.
The output stage should be OK but,in addition providing the correct supply voltages to the control and drive circuits, you would also need to modify the output voltage regulator system and protection circuits to enable them to make them compatible with the lower output voltage.
An interesting project for the hardened experimenter with adequate experience and test equipment but not a job to be undertaken lightly!
Jim
The hardest part is to get a copy of the schematic of the drive so you dont have to guess what is going on in it.
The phase rotation sensor and phase loss sensors would have to be bypassed if you are running on single phase.
The current sensors would probably be ok since the high power electronics ratings are already matched for the current setting of the sensor. The voltage sensors would have to be modified for the lower voltage on the DC buss.
The control circuits power supply would have to be modified to take the lower ac input voltage unless is was a switching supply with a wide range of input voltages.
the final thing is that higher powered drives are expensive, even the
480 volt ones since there is a continous demand for them. A new 40 hp drive gets up in price.John
Most modern VFDs use a little inverter off the main DC supply, not a separate 60 Hz transformer. They also might have an indervoltage sensor. I cannot think
Yes, they most certainly do, and will shut down below some particular voltage.
Well, the little inverter could be rewound, or replaced with a
60 Hz transformer, once you figure out the several DC voltages it supplies to the works. Then, you could track down the resistor voltage divider for the voltage sensing and change that. You would have to convert various things when programming the drive, because it still thinks it is producing 480 output. All the current logic should work fine without any changes or conversions, and Hz is still Hz. If you could find a 5 Hp 480 V VFD, that would make a dandy 1 Hp 240 V VFD, if the above conversions weren't too hard to accomplish. If you found a pallet of 480 V VFDs of the same make and model, this could be a very profitable exercise. I'm not sure it would be such a great deal to have to trace all this out on a one-by-one basis.Jon
It would say something like "UV" in the display, and refuse to do anything.
Jon
The smaller drives, ie. 1 - 15 Hp, in the US at least, never seem to have PFC. This may be totally different in Europe. Many of the bigger drives have an inrush surge limiting circuit that may not switch over properly at half voltage - but they may just be a timer circuit off the control power.
They derive all this off the control power, so it should be fine, once you get the control power supply working right.
Jon
Yikes! 40 PLUS Hp? Even derating it to 20 Hp, assuming no losses, and just steady state running, would draw 15 KW, and 62 A at 240 V. If the starting surge was only 100%, that would take it up to 124 A. You won't need much else on in your entire house to trip the service entry breaker.
Jon
There is no "output voltage regulator". The CPU measures DC bus voltage and calculates the correct pulse width to get the desired voltage. If you hack the resistor voltage divider so the CPU reads the expected voltage when it is really half of that, it will calculate the right pulse width. You still tell it it is running a 480 V motor, and it dutifully puts out 240 V due to the two changes (reduced DC voltage, incresed sense voltage) cancelling out.
Iggy is INDEED a hardened experimenter, who hacked a DC TIG welder into a square wave AC TIG machine. So, I think he COULD do this. I don't know if it makes any sense to do just one unit, but if you had a bunch of the same model, it could be quite a successful project.
Jon
I can't imagine any reason a VFD would have a phase sequence sensor, as it just gets rectified to DC anyway. Some drives do, and some don't have a phase loss sensor. But, since Iggy was talking about 40+ Hp drives, then they often do have that.
That's only one resistor, but you have to know enough to find it.
It is customarily a switching supply off the main DC bus on most modern drives. And, they usually are not very wide range.
Jon
My TIG welder (I think Iggy's as well) will happily suck down 100A at
240V, and for longer than that motors startup too. I haven't had any problems yet.
Mine draws about 60 amps.
i
Derate it to 20 HP due to voltage, then derate it to about 66% of that due to single phase, you get just 12-13 HP. I routinely start a 10 HP motor at home (in my phase converter) and that is never a problem (60 A circuit).
I read all your posts in this thread with huge interest. I will keep trying to get a cheap 480v drive to play with. I estimate my chances of success at about 20-30%. But I will learn something useful.
i
Look for a transformer while you're at it. They should be readily available, my own inventory has a number from 1KVA to 15KVA. They typically have dual pri and sec windings so 240/480:120/240 however you care to connect them.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.