Re: Dc Electric Switch Question

Posted by John T on May 20, 2019 at 07:07:45 from (45.16.200.171):

In Reply to: Dc Electric Switch Question posted by vicinalvictor on May 20, 2019 at 04:50:35:

Yet more information...….

First, a general purpose "switch", say to reverse polarity or whatever, but NOT intended or rated for motor starting, IS NOT NECESSARILY THE SAME THING AND IT MAY NOT BE CAPABLE OF ACCOMPLISHING THE SAME RESULTS AS AN ACTUAL TRUE HP AND VOLTAGE AND CURRENT RATED "MOTOR STARTER"

A 800 watt 36 volt motor draws 800/36 or 22 amps BUT that don't mean a cheap straight "switch" (NOT motor starter rated) even if rated for 30 amps will last very long if used to start n stop a motor. Now if its ONLY used to switch polarity no switched load, no starting or stopping, it can suffice for that purpose. Reason is when a motor starts and when it stops theres a lot more current and/or arcing which is hard on contactors.

An actual motor starter has contacts that are rated for the extra current and arcing when starting and stopping a motor PLUS it has thermal overload protection to shut down in the event of overheating or excess current draw THATS TO PROTECT THE MOTOR

MORAL OF THE STORY A cheap toggle switch rated for say 30 amps and 36 VDC "may" work for a while to start n stop a motor (say its a DPDT Center OFF switch) BUT an actual HP and DC Voltage and Current Rated "motor starter" may be whats needed for the reasons described above. Of course, if there's a heavy duty toggle switch with center off rated for sufficient HP and Current and DC Voltage designed to start n stop a motor GO FOR IT NO PROBLEM. Some motors have their own built in thermal overload protectors. I have seen similar switches used on the small DC motors to say raise n lower an RV travel trailer (they reverse plus start n stop a DC motor!!!) but I have seen them go bad, perhaps they didn't have the necessary ratings ???

DISCLAIMER for those nit pickers or people who love to play "gotcha" NO WARRANTY THIS IS ACCURATE WHATSOEVER. Its been nearly 50 years since I was an Electrical Engineer for the Century Electric Motor Company and my old brain is worn out and I have forgotten things LOL YOU DONT SAY. But hey I try my best to help whenever and the best I can

Best wishes n God Bless Yall

John T

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