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New Motor Issues on Mori Seiki Lathe


Oct 27, 2022
I replaced the motor on my Mori Seiki MS-850 lathe that I'm trying to get fired up. I replaced it because it was spooling up very slowly, and I took off the old motor and it was full of what looked like drywall dust and in bad shape. So I replaced it with a brand new WEG that fits the same frame size (IEC 112M).

The issue now is that when I turn it on, the contactor fires rapidly on and off, and then it quickly settles in and the motor runs smoothly. This is with the motor completely without load. The transformer is spitting out 120V to the contactor coil. The old motor turned on fine, but spooled slowly when connected to the lathe, but this issue wasn't present. all three phases have 240V at the motor when it's running. I'm at a complete loss on what the issue might be. I'm wondering if the contactor or thermal relay might be bad and can replace them, but I wanted to ask here before springing for new contactors and a relay. One curious thing is that when the motor is coasting to a stop, but still moving, and I turn it on again, the issue doesn't happen. It makes me think it has something to do with the inrush current, but I don't know where in the system it could be failing other than the contactor or relay, which are both rated for this load. Here is a link to a video of the problem. you can see it happening a few times and then at the end I flip it on while the motor is coasting.

The original motor was rated 3.7kW (5HP) but this frame size now is 4kW (5.5HP). The new motor is a WEG 00418ET3EAL112M-W22. Photo below of the data plate. Most 3 phase motors I've wired have been an internal Wye configuration, but this is wired delta, and the low voltage wiring is a double-delta. I'm not sure if the inrush current on this would be too high to handle...? But it's not even under load yet.

I'm running it with a North American rotary phase converter, Model PL-10, which is rated to start heavy loads at 5HP. That is on a 50A single phase 240V circuit.

I'm very appreciative of any thoughts folks have to help me solve this one


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Are you pulling the transformer wires from the weaker generated leg?

Always run controls from the incoming wires.
Good point, I will check that.
I was just digging into the transformer actually. Here is a photo of how it's currently wired. I saw another post that jumped the high voltage coils like the way that I'm drawing. Should I jump the high voltage coils like this?


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If your source is "220VAC", then that should be the way. If it were 440, then the middle two would be jumpered together.
JST that fixed it! One leg of the transformer was connected to the generated leg. Switched it and it fires up no problem.
Thank you! This thing is almost ready to rip