Normal operation for a rotary converter?

[MillWeld]

My 5 HP 3 ph planer's power source is a rotary conveter from WNY (model RK07) with a 7.5 HP 3 ph idler motor. The planer is operating fine but I have questions about the observed phase voltages upon startup. The voltages for L1-L2, L1-L3 and L2-L3, respectively, are:

Upon turning RPC on: 238 248 234
Upon turning planer on: 210 125 140
2 seconds later: 233 220 220

Are the low voltages for the manufactured phases immediately at startup due to undersized components or is this normal? I have asked WNY these questions but have gotten no answer yet.

How much time do I have before the 30 amp breaker powering the whole setup trips?
Bob

 

[LD1]

I am no expert, but I think that is normal. Remember you are "creating" 3PH. So a drop is to be expected when you initally apply the load.

HOW much drop, well, I'd wait or keep trying to get an answer from the MFG.

Motors always have a high start-up current. It is just showing up as a voltage drop.

As to the 30A breaker tripping, well.......I dont know how close you are to tripping. Because JUST knowing voltage ONLY tells us nothing about how many amps it is drawing. And it is amps that trip a breaker, NOT voltage.

So...Put an amp clamp on the 30A breaker and see what it is acutally pulling.

Personally though, I think you are fine. After the 2seconds and the motor is up to speed...your voltages look fine.

Another question on a side note....Is this the only peice of 3PH equipment you have?? And is the PC new and did you buy it just for this??? Because a 5HP 220v SINGLE phase motor would have been the route I'd have taken if this is the only peice of 3PH equip you have.

 

[MillWeld]

The drop on the line voltage looks typical to me but it is the manufactured phases that surprise me. They are ~50% drop. That looks too big to me.

Another question on a side note....Is this the only peice of 3PH equipment you have?? And is the PC new and did you buy it just for this??? Because a 5HP 220v SINGLE phase motor would have been the route I'd have taken if this is the only peice of 3PH equip you have.

It is the only 3 ph I have. The planer came with the 3 ph motor and I bought the idler for $17.50 so it was a "no-brainer" at the time to stick to 3 phase.