imported_brian_m
Cast Iron
- Joined
- Jun 25, 2006
- Location
- Oregon
I've reached the stage of building the RPC for my lathe renovation. I ran a hacked together version of the basic RPC today and obtained a strange current reading for the generated phase of only 1.2 amps (measured with a Fluke clamp-meter).
First the system. I have left out several items that will be in the completed system. The 220V supply is from a 200 amp main panel. The RPC idler is an older Dayton 1700 rpm 15HP industrial motor. The machine motor is a new Marathon 1700 rpm 10HP motor. The idler motor starts easily from a 1 HP pony motor (this is a temporary arrangement). The idler motor runs smoothly and surprisingly quietly. Each supply leg from the main panel connects to a terminal block with several outlet ports. The idler motor feed is also connected to this block as is the output leg for that phase. To be clear, the input, the output to the 3-phase contactor and the supply to the idler motor share the same terminal block. This applies to both of the supply legs. The generated phase of the idler joins the two basic phases at another terminal block and the three legs are fed to the output contactor. When the output contactor is closed the machine motor starts with no hesitation at the idler motor then it continues to run smoothly.
These are the supply leg currents. (all readings with the machine motor running but no belt on the motor).
Line 1 41.2 amps. Line 2 41.6 amps.
Output current to the machine motor.
T1 16.4 amps. T2 1.2 amps. T3 16.1 amps.
Output volts to the machine motor.
T1 to T3 238.3 volts. T1 to T2 214.4 volts. T2 to T3 207 volts.
Do I have a fault on the system, is my wiring method wrong or is this just a matter of balancing?
Strangely the whole system works very smoothly. The idler supply does not even notice the machine motor being connected and the machine motor starts and runs very well.
Should I panic or just proceed with the project?
Thanks, Brian
First the system. I have left out several items that will be in the completed system. The 220V supply is from a 200 amp main panel. The RPC idler is an older Dayton 1700 rpm 15HP industrial motor. The machine motor is a new Marathon 1700 rpm 10HP motor. The idler motor starts easily from a 1 HP pony motor (this is a temporary arrangement). The idler motor runs smoothly and surprisingly quietly. Each supply leg from the main panel connects to a terminal block with several outlet ports. The idler motor feed is also connected to this block as is the output leg for that phase. To be clear, the input, the output to the 3-phase contactor and the supply to the idler motor share the same terminal block. This applies to both of the supply legs. The generated phase of the idler joins the two basic phases at another terminal block and the three legs are fed to the output contactor. When the output contactor is closed the machine motor starts with no hesitation at the idler motor then it continues to run smoothly.
These are the supply leg currents. (all readings with the machine motor running but no belt on the motor).
Line 1 41.2 amps. Line 2 41.6 amps.
Output current to the machine motor.
T1 16.4 amps. T2 1.2 amps. T3 16.1 amps.
Output volts to the machine motor.
T1 to T3 238.3 volts. T1 to T2 214.4 volts. T2 to T3 207 volts.
Do I have a fault on the system, is my wiring method wrong or is this just a matter of balancing?
Strangely the whole system works very smoothly. The idler supply does not even notice the machine motor being connected and the machine motor starts and runs very well.
Should I panic or just proceed with the project?
Thanks, Brian