Replacing a 3ph motor with single phase

its

Jogging

short

time

Two easy answers: a. use a cap run motor b. use a current sensing start switch

Also this will almost always be within the start time of the jogger motor.

?-)

ression that starting all the smaller motors first will help prevent the co nverter from being overloaded during start up of the largest machine. "

Maybe I had that bass akwards. If all the motors on the line help the proce ss, it SHOULD better to start all the small ones fisrt.

Somehow, at the time it seemed to make sense the other way. Also, I seem to remember somme designs with somewhat of a flywheel. Only a few.

Thing about starting all the small stuff first though is the whole thing is under a normal load, and then has to take the surge. Also, alot of people who have these things are home shop achinists who might be working alone an d have no reason to have more thatn one machine running at the same time. M any probably only have one three phas machine in the first place.

I just relayed what I was told. If it is wrong I appreciate the correction.

start the last big motor. "

I kinda agree. there is a such thing as power factor, and mayber them suppl ying some current during the startup of big Bertha. Drawing on say five of them, if they help to keep the phase right, maybr it does do something.

However, we are not generally taling one 25 foot horizontal boring mill ver sus the other three phase devices like the IBM Selectrics, the copyting mac hine and, well, the lighting.

If you got three phase lighting and no three phase power there is somethnin g wrong. Usually, there is a eire to run one machine, like a Bridgeport in your basement. According to what I've heard, it is really rare that you use all the current capacity. Nice to have it of course, but you only need it for a split second. The only time running the current goes up is when you b ury an endmill into some tough material. Maybe the OP's associate is the ty pe to do that.

Maybe. On manual machines which is what people use to make homeade guns and shit like that, you never need all that umch power. When you run productio nn is when you pull the juice. Maybe that guy is running production in his basement.

Believe it or not that means "desire".

Rotary converters are more forgiving of start-up currents, electronic ones less so.

If the converter/inverter was unable to supply the full start current, as indeed may well be the case in many instances, it would be wise to start the largest motor first to minimise peak current draw and get any loss of regulation done with quickly, then allow the others to come onstream.

I have had the condition where an electronic inverter wasn't man enough to bring motor up to speed with a light load, a load that I couldn't remove, where it just ended up spinning slowly and getting very hot.

Many electronic inverters have a frequency ramp to help with running up motors!

Your point is valid- I'd be less concerned about the switch than with the start winding itself -second thoughts about "rms HP" The motor would have to be cap start (not necessarily cap run)-yes, there may be a high current at the time that the switch operates Cap run optimises operation near synchronous speed -not at start. How long will the motor run, when jogging? Does it get up tYour point about the

There is another problem- mounting the motor- it will be larger physically than the polyphase motor.

It also comes down the starting torque needed -any idea? Don't rule out DC motors fed from an ordinary diode bridgr-

motors! "

this is what the OP's customer fears. He, well if he took a VFD it would be a DC motore with a three phase genny on it. that's th way I gt it.

How about a hydraulic motor or actuator, accumulator and small pump driven by single phase?

-- Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com

------------------------------------------------------------------ Life is like an analogy.