Rotary phase converter question
Hello everyone,
I just bought a Mazak QT8 CNC lathe. It came with an American Rotary AD10 converter and I put it in my residential garage. Everything is wired and operational, and when demand is low (reduced rapids and slower spindle speeds) everything works fine. But when performance is required, I get a X axis servo alarm. I suspect the rotary phase converter is undersized and allowing the voltage to drop.
Here is the question. Can I add a 3 HP 3 phase motor to run with the idler to help prevent the problem? I have the 3 hp motor on the shelf for another project, so it would be easy to try it. I also have a 3 HP knee mill currently wired with a static converter. It would be easy to remove the static and wire it to the rotary, as well.
I seem to recall the loads will add up to help start larger motors, but my research today has failed to turn it up.
Thanks!
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Re: Rotary phase converter question
You alarm is probably an over voltage from the wild leg, a normal problem with RPC's it will kill the servo drive with timeOriginally Posted by Ron Thompson
Adding another motor would only make it worse, running a RPC for any CNC is never a good idea, some CNC machines work ok with a RPC but most will have some kind of problem, Phase Perfect is the only real way to get good reliable 3 Phase power from a Single Phase connection
Mactec54
Re: Rotary phase converter question
The RPC is rated for CNC. I'll check the voltages first chance I get. Thanks!
Re: Rotary phase converter question
OK, I did some checking. Attached is the voltage data under various conditions.
It looks to me like the additional idler affected the balance, as I would expect. (the wild leg voltage actually dropped.) So I assume I could add capacitors to re-balance and bring the voltage up..
I loaded a program and was able to rapid without an alarm, so progress. With the machine just running the spindle,
I was able to get the spindle to about 3500 rpm before it alarmed. The max is 4000. So better, but not quite there, yet.
My conclusion is I could add maybe a 5 hp idler in addition to the existing 10 hp idler and re-balance with additional capacitors.
Any thoughts, anyone? Thanks.
Re: Rotary phase converter question
I don't know Ron, those voltages aren't off by significant amounts. Maybe something other than voltage is going on. Not sure what to suggest.
If it was a voltage balance issue, I would balance with caps rather than go to a 5-10HP idler.
Steve
Re: Rotary phase converter question
I lucked into a WEG brand 3 phase 10 HP motor from an Ingersoll Rand air compressor for $75. I just got it wired to the 10HP rotary phase converter and it works OK, just a little noisy. I may try to reverse it and see if it is any quieter, or it may need some grease.
I have a bunch of run caps I bought off of Amazon.com, but haven't tried to balance it, yet. The voltages are a little lower, indicating the need for balancing.
L1 TO L2 = 245.0
T1 TO T2 = 244.9 (Same as L1 and L2 but past the contactor)
T1 TO T3 = 239.7
T2 TO T3 = 234.0
I am out of time for today, I'll update this when I have more data.
Re: Rotary phase converter question
I bet it gets quieter when you balance with the caps.
Steve
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