This post is about a RCP that uses a 7.5HP idler and drives a 5HP lathe motor. All motors are wired for 230V.
I used the FitchW method to balance phases and got these results which are textbook perfect according to the method:
Idler only:
Vab = 243
Vac = 262
Vbc = 262
My lathe came equipped with a Furnas reversing contactor setup and solid state overload relay (Furnas 48ASF3M20).
The problem is that the overload trips during lathe motor startup. The lathe (Monarch 16CY) has a clutch so the motor starts unloaded other than spinning up its own mass and the belt drive system. It only trips on the 2nd and subsequent starts. If it rests a few minutes, it will start without tripping. It also trips if all capacitors are removed but it will start 3-4 times in succession before tripping. Once started, the clutch can be disengaged and the motor has no problem driving the lathe. The overloads have never tripped during operation once the motor made it past startup.
Can one reliably go by the nameplate data and overload relay setpoint when using a RCP? Is if normal for a motor to operate above its FLA when running on a RCP? Any other troubleshooting suggestions?
EDIT:
When the 5HP is running with the clutch engaged (lathe is not turning):
Vab = 242 V
Vac = 238 V
Vbc = 236 V
Ia = 6.3 A
Ib = 6.7 A
Ic = 4.2 A
With the lathe spinning at 600RPM:
Vab = 242 V
Vac = 226 V
Vbc = 239 V
Ia = 8.3 A
Ib = 10.2 A
Ic = 4.7 A
My meter doesn't have a max-hold feature but I saw current as high as 92 Amps during startup of the 5HP motor during startup.
I used the FitchW method to balance phases and got these results which are textbook perfect according to the method:
Idler only:
Vab = 243
Vac = 262
Vbc = 262
My lathe came equipped with a Furnas reversing contactor setup and solid state overload relay (Furnas 48ASF3M20).
The problem is that the overload trips during lathe motor startup. The lathe (Monarch 16CY) has a clutch so the motor starts unloaded other than spinning up its own mass and the belt drive system. It only trips on the 2nd and subsequent starts. If it rests a few minutes, it will start without tripping. It also trips if all capacitors are removed but it will start 3-4 times in succession before tripping. Once started, the clutch can be disengaged and the motor has no problem driving the lathe. The overloads have never tripped during operation once the motor made it past startup.
Can one reliably go by the nameplate data and overload relay setpoint when using a RCP? Is if normal for a motor to operate above its FLA when running on a RCP? Any other troubleshooting suggestions?
EDIT:
When the 5HP is running with the clutch engaged (lathe is not turning):
Vab = 242 V
Vac = 238 V
Vbc = 236 V
Ia = 6.3 A
Ib = 6.7 A
Ic = 4.2 A
With the lathe spinning at 600RPM:
Vab = 242 V
Vac = 226 V
Vbc = 239 V
Ia = 8.3 A
Ib = 10.2 A
Ic = 4.7 A
My meter doesn't have a max-hold feature but I saw current as high as 92 Amps during startup of the 5HP motor during startup.