Members DrmCa Posted July 15, 2019 Members Report Posted July 15, 2019 (edited) One thing to remember is that if after wiring a 380V motor to run on 220V it runs at lower RPMs, then it could overheat from the lack of air circulation. Edited July 15, 2019 by DrmCa Quote Machines: Mitsubishi DB-130 single needle, Kansai Special RX-9803/UTC coverstitch, Union Special 56300F chainstitch, Pfaff 335-17 cylinder arm walking foot, Bonis Type A fur machine, Huji 43-6 patcher, Singer 99 hand cranked, Juki DDL-553 single needle (for sale)
Members TonyRV2 Posted July 16, 2019 Members Report Posted July 16, 2019 16 hours ago, DrmCa said: One thing to remember is that if after wiring a 380V motor to run on 220V it runs at lower RPMs, then it could overheat from the lack of air circulation. Nah....A.C. motors run at an rpm which is determined by the line frequency, not the voltage. More specifically at the line frequency minus the motor's "slip". Now it is possible that the slip is different between running at 380V or 220V, but this would be a minimal difference as slip is usually less than 10%. Quote Tony VRifle River Leather Ogemaw Knifeworks There are two individuals inside every artisan...the poet and the craftsman. One is born a poet. One becomes a craftsman.
Members DrmCa Posted July 16, 2019 Members Report Posted July 16, 2019 Depends on the voltage drop. I would not write the above if I did not witness it with my own eyes. Quote Machines: Mitsubishi DB-130 single needle, Kansai Special RX-9803/UTC coverstitch, Union Special 56300F chainstitch, Pfaff 335-17 cylinder arm walking foot, Bonis Type A fur machine, Huji 43-6 patcher, Singer 99 hand cranked, Juki DDL-553 single needle (for sale)
Members TonyRV2 Posted July 16, 2019 Members Report Posted July 16, 2019 34 minutes ago, DrmCa said: Depends on the voltage drop. I would not write the above if I did not witness it with my own eyes. Again, an A.C. motors r.p.m is determined by frequency, not voltage. I would not have written the above had I not been an automation engineer and taught electrical engineering for 32 years. If you witnessed that a motor had slowed down under the OP's posted conditions, then it was loaded. However, this would increase the motors slip which then increases the back EMF to the windings which increases the torque which brings the motor back up to speed. However, if the motor is overloaded it cannot recover. This may describe the situation you'd witnessed. Quote Tony VRifle River Leather Ogemaw Knifeworks There are two individuals inside every artisan...the poet and the craftsman. One is born a poet. One becomes a craftsman.
Members dikman Posted July 16, 2019 Members Report Posted July 16, 2019 (edited) If I had a 3-phase motor I wouldn't mess around with rewiring it I'd buy one of those magic boxes that lets you run a 3-phase on single phase and also acts as a speed controller. Perfect solution, in my opinion. Edited July 16, 2019 by dikman Quote Machines wot I have - Singer 51W59; Singer 331K4; Seiko STH-8BLD; Pfaff 335; CB4500. Chinese shoe patcher; Singer 201K (old hand crank)
Members Matt S Posted July 17, 2019 Members Report Posted July 17, 2019 10 hours ago, dikman said: If I had a 3-phase motor I wouldn't mess around with rewiring it I'd buy one of those magic boxes that lets you run a 3-phase on single phase and also acts as a speed controller. Perfect solution, in my opinion. I had the same thought when I bought a 3-phase splitter. Turns out those magic boxes release the magic smoke if any switchgear between the motor and the controller changes state while it's running. They also need to be tuned to the load and aren't really recommended for running multiple motors. My machine has 4 motors, all different RPMs and power requirements. I left the electrogubbins in the control cabinet alone and just built a static converter. Quote
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