DIY Rotary converter problems
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  1. #1
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    Default DIY Rotary converter problems

    I have an old 5 HP 3 phase motor that I have been using to run my 1940s Sebastian lathe and 1983 Bridgeport Mill. It is the basic old school set up that requires me to use a rope to start it. I have been using this setup for almost 20 years with no issues. Yesterday I went to start it and it took a little more effort to get it started but it started and sounded like it was a full speed but my mill and lathe were way down on power. I am very limited in my electrical knowledge. So is it possible for the motor to run but not supply full power to my machines? Any help is greatly appreciated.

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    Make sure you have 240v at breaker, maybe time to re-inspect all connections, maybe while your in there ohm your windings?

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    Possibly bearings going south?

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    Turn the idler by hand... does it spin freely? If it's binding, then it will drag, and be well below it's proper run speed for 60hz operation, and as a result, your generated leg will be way, way low.

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    The loads (mill and lathe) would still run even if the RPC was off, as long as it got them started. Running single phase, you might not notice a power issue unless you were using max power for a cut.

    Also, if the RPC is not running up to speed, it should be pulling quite a bit of current, and probably would get hotter than usual fairly quickly.

    Do you have any equipment with which to measure voltage and/or current?

    If you do, it would be useful to measure the voltage from the generated leg to the others (the pass-through legs) with no other motors turned on. Also the input current to the RPC could be helpful.

    If those look normal, then the generated leg voltage while the RPC is powering one of the machines would be helpful as well.

    Does the RPC have any of the fancy balancinc capacitors? (I assume not given the rope start basic nature of it).

    The rope start , no frills type RPC is normally very trouble free unless there are bad connections or a problem inside the motor.

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