What's new
What's new

RPC + 3-phase transformer

specfab

Titanium
Joined
May 28, 2005
Location
AZ
I am using a 10 HP rotary converter that is providing pass-thru voltage of about 240V on two legs, and something on the order of 265V on the generated leg. This is a commercial converter that I acquired along with a Tree J325 CNC knee mill.

The Tree input power spec is 230V +/- 5%, and I have run into a power-up problem (servos won't turn on) on the machine that may have been caused over time by the use of this converter, by previous owner and then me. The Tree employs a shunt-trip input breaker for the 3-phase power, and it now trips immediately upon application of power to the servo cabinet. Not a promising sign, in my estimation. The control unit is powered separately by the two 240V legs, and doesn't show any issues.

I want to get my power situation squared away before I resume troubleshooting the Tree problem. My questions are these:

-- What should I look for in the converter setup to reduce the voltage of the generated leg?
-- OR, will a 3-phase transformer that is fed with unbalanced voltages from the RPC provide any averaging function to help the individual legs get closer to each other?
 
Disconnect ALL the "balance capacitors, and check the voltage. It should now be lower than the input voltage. Add back enough to get to equal or just a bit over the input voltage.

Since your actual source voltage is high, you start out over the "asking" voltage of your machine, well into the tolerance, and you might benefit from a buck transformer on the RPC input. But try the capacitors first.
 
Disconnect ALL the "balance capacitors, and check the voltage. It should now be lower than the input voltage. Add back enough to get to equal or just a bit over the input voltage.

Since your actual source voltage is high, you start out over the "asking" voltage of your machine, well into the tolerance, and you might benefit from a buck transformer on the RPC input. But try the capacitors first.

Thanks for the info. I assume you are saying:
Disconnect capacitors, reconnect where needed to bypass the caps, start converter, then check output voltages with converter in operation(?)
Yes, the voltage from the mains is already in the plus-tolerance band, so care is needed for a solution. Or at least the right hardware.
Any observations on the behavior and output of a 3-phase transformer when input is unbalanced? Are the outputs proportionally unbalanced. or is there some sort of smoothing between phases thst will provide some equalization among the outouts>
 








 
Back
Top