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Good info, thanks all. Neil

Electricpete I would agree that the the majority of the common mode current entering the motor terms gets to ground in the stator. The larger question remains, how to identify or separate bearing current from the stator ground current. I would expect the signature of the bearing current to be...

Is anyone aware of documented research which relates bearing life to the magnitude of rms or peak(pulsing) current? I can measure and reduce common mode current near the motor terminals and must assume that most of the common mode current in this location particularly the peaks (current...

my understanding is that large wind turbines are expected to develop about 33% of nameplate power on a continuous basis converted to KWH. If that assumption holds true you may be able to deliver 200 watts on average. Neil

Keep us informed of your progress, I'd be intrested to know when it's all done how much it costs to set up a 600w wind supply. Neil

This is a cost/benefit analysis. "Using multipulse rectification is usually the least expensive way to mitigate harmonics". Come on, line reactors are the least expensive way to mitigate harmonics. This analysis can't be made without costs, target THD and realistically you need to know the...

EEPROM, I can't speak to breaker use as we don;t use them in this capacity. We build 508A panels all the time and we have a letter written by a UL Engineer that clarifys our requirement. We use 2 current limiting fuses in series, per phase. Both fuses are class T. The source side fuse is...

Take caution using current limiting fuses. Ul does not recognize the current limiting capability if the fuse is located in a branch. Neil

A 15hp 3 phase VFD can be supplied from a single phase source then provide a 3 phase output to the motor at 7.5hp. This is a fairly common application. Should work well as long as you don;t need to change voltage. Neil

there is another possibility. If this is a 3 phase choke with a 3 leg core, then if the leads are grossly over sized by cross section, you can have a high amount of common mode current. Such a reactor will saturate in the yokes from this condition. Need to reduce the common mode current. This...

I'll qualify my statement by saying that the VFD cable we have test experience with was purchased around 10 years ago and frankly I don't know if it has individually shelded strands. But we did ground the shield and our results were that the overvoltage ringup was not as bad as the armored cable...

I think you will find a properly sized dv/dt filter with armored cable (again properly sized) to be a more cost effective solution. The problem with the VFD cable is that it is basically jus protecting itself. You will still get ring-up at the motor terminals. One of the really big problems I...

These transformer commonly see 250% of rated current for relatively short periods say 1.5 hours, mainly in the morning when everyone wakes up. Then in the afternoon again a high overload maybe 150-200% but lasting a few hours, then 10-20% for about 8 hours,... The oil provides a significant...

It's kinda like putting a 60w light bulb in a socket where previously there had been a 100watt bulb. The new bulb only draws 60watt regardless of the circuit and socket's ability to deliver 100w or more. Neil

With regards to residual flux. This gets to my point about the likelihood of a transformer saturating much more quickly than an inductor. Inductors typically have much lower permeabilit, made so by air gaps. The air gap allows the residual flux to seek a very low level. Unlike transformers...

I believe, UL508A table 28.1 is going to assume the temperature of the air in the enclosure to be 40 to 50C. I've heard arguments both ways but believe it's customary for UL to allow 50C in the ICP enclosure. Neil

Well, like I said, it probably isn't saturating but keep in mind that the inductance changes (drops) as the core nears saturation. This is because the permeability of the steal drops with flux density. So effectively as the inductor reaches saturation, the inductance is falling and the effect is...

It probably would not saturate an inductor, maybe a transformer. But the air gap in the inductor covers a lot of sins. However, even if it had saturated the inductor, that shouldn't prevent the motor from running. When the core saturates, the inductance goes to the air core inductance of the...

jghrist! you've written the magic words, "renewable energy". If it's in the name of renewable energy, they it shall be done and cost will not be an obstacle. Politicians will be falling over themselves to throw money at such a project. Neil

Sorry, I just scanned the thread so excuse if this has been suggested but why not use a 3 phase motor and VFD but supply the VFD with single phase. This is a fairly common solution. Just upsize the VFD 175 to 200%. so a 7.5hp VFD would drive the 4hp 3ph motor. Plenty starting torque and speed...