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Thread: Magnetic Starter
11-18-2006, 01:50 AM #1
Hello, I recently developed a problem with one of the South Bends in my high school metal shop. Over the summer it decided to stop starting. The magnetic starter seems to be the problem. Is there a magic bullet? I haven't been to South Bend to get the history on this particular machine. I do have the serial number thanks to reading numerous posts on this site. I have some pictures. I sent pics over to the local motor shop about a month ago. He indicated he really needed to see in person what I have. That hasn't happened yet, since he won't return my calls anymore, I think that trail has dried up. I have three totally different machines in the shop. They all have apparently been there since 1967 or before. The previous instuctor stopped by.
11-18-2006, 08:21 AM #2
Most magnetic starters are not too hard to troubleshoot. Yours should have devices called heaters inside. They are sort of like fuses and if melted, stop the flow of electricity to the circuit. There should be a coil inside the starter which provides the magnetic attraction inside the starter to close the contacts. If the coil is bad not much will happen with the starter. You can check it with an ohm meter if you have one. It's possible the contact assembly is burned to the point that even though everything else is working the electricity can't make it through the contact assembly and the motor won't start. If this information doesn't work I'd advise you to get a licensed electrician to look at the starter.
11-18-2006, 03:17 PM #3
It seems strange that you are having such a problem getting this serviced. It's the technology downstream from the starter that generally causes the most headaches. Motor starter applications are straightforward, and you should be able to locate a competent technician to troubleshoot/repair/replace the starter quite readily.
Like Bob said, your starter probably has heaters, but they do not function like fuses (though it is possible for them to fail open, like a fuse). They are basically resistance heating elements which trip an overload contact when a given current level is exceeded. The overload contact for each pole is wired in series with the other contacts and the starter coil, so that if any one of them opens, the starter drops out.
You didn't state the motor voltage, or whether it's single or three phase, but if the coil operates at a lower voltage than the motor, the problem may be with the transformer which supplies the coil voltage -- a fairly simple fix.
You say this machine is in a high school shop? Does the school have a maintenance technician, who might at least know of someone that services motor controls? Again, it's kind of surprising that you are having such a hard time getting someone interested. This is a decidedly low-tech electrical issue.