Centec feed motor starter switch

I use a static phase inverter to power both motors of my Centec 2b. The motor for the power-driven table is 0.125hp, 1350rpm, FL amps per terminal 0.28A. I believe the existing starter switch for this motor is faulty because after a few minutes use, even with light cutting, the overload protection triggers, though I’m pretty sure the current is not reaching anywhere near full load. Any ideas how I can check this, or what replacement starter I can buy?

Hello Pete,

I am wondering if the trip is caused by overload or a low voltage relay (for protection against restarts after power loss).

If the latter, changing around the phase connections to your motor might just sort your problem.

RAB

Thanks RAB

I eventually measured the currents on each phase and was rather taken aback by how different they were. Benn scratching my head ever since.

I hadn't considered the low voltage relay, and I guess there must be one because the table motor switches off a few seconds after I switch off the main motor. Reminder to myself - stick my head in the casing and sketch out the circuit!

Pete

Might it be the capacitance values in your converter causing the eneven currents?

I'm no expert on anything but that seems, to me, to be a likely area for investigation.

I also think its the capacitor values. Has all been OK up to now ? Can you check the resistance of the motor windings using an Ohmmeter and it insulation resistance using a "Megger " to illuminate the motor .I have wired three ammeters into a converter circuit and like you, was surprised by the differences in line currents and voltages.I then wired a large rotary switch in circuit so that I could adjusted the capacitors, with the motor running, so that the voltages and currents in each line was about the same. I also found that when the motor sounded/hum normal the capacitance was about right. But, all changed when load was applied. I found the values are only correct for one setting, near enough generally. I think modern converters will have some automatic means of adjusting capacitor values.I've never got round to fitting a pilot motor which idles way behind the lathe cabinet equalising the voltages, but apparently they are a good idea. Think of a triangle with each side of the same length, balanced 60 degrees, then another with un equal sides.I'm pleased Inverters came along.John