Single Phase motor starter w OL protection?

I am installing a single phase, 1/20 hp gearmotor into an existing machine, and I am searching for a motor starter with thermal protection. Panel space is tight, as always. Just wondering if those of you who do this often could reccommend a brand for this?

The motor is a Bison 016-562-0084.

Thanks in advance.

PLCRookie said:

I am installing a single phase, 1/20 hp gearmotor into an existing machine, and I am searching for a motor starter with thermal protection. Panel space is tight, as always. Just wondering if those of you who do this often could reccommend a brand for this?

The motor is a Bison 016-562-0084. Thanks in advance.

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Generally on small motors like this a "regular" motor starter ie overloads etc is not used. I am not sure you can get them this small. A quick n dirty check may be your friendly Grainger catalog.

You can protect the motor with slow blow fuse rated for 110 to 125% of full load amp. You can pick FLA off nameplate or run it under normal operate condions and measure amps then size fuse off that.

Dan Bentler

Dan,

Thanks Dan.
That is what I am finding also. Could not see a 45mm size for this. I do not do this type of thing regularly, so I was unsure. I knew I could use a relay with a fuse, but just thought maybe there was someone out there I was not familiar with.

Thanks Again

I have never seen a conventional starter on a fractional HP motor,,they don't draw enough current or use enough power to "need" a starter, which is basically a large electromechancal relay. Just hook it up direct with the correct fuse in series.

PLCRookie said:

Dan,

Thanks Dan.
That is what I am finding also. Could not see a 45mm size for this. I do not do this type of thing regularly, so I was unsure. I knew I could use a relay with a fuse, but just thought maybe there was someone out there I was not familiar with. Thanks Again

Click to expand...

Another thought: IF you are controlling this motor from a PLC output you may want and probably should use a relay whose output will handle the motor current - this will prevent blowing or prematurely burning out the PLC output.


Dan Bentler

The purpose of a thermal overload is mainly to save an expensive, high horsepower motor. A typical failure would be a bearing. A motor will start drawing more current with a bad bearing. With fuses or a breaker, there's a good chance the bearing would go to total failure, tearing up the shaft, housing, or even burning up the motor before the breaker trips. A thermal overload is much more sensitive, tripping as soon as current draw goes up just a few percentage points.
For pumps, the thermal overload minimizes damage possibly allowing a rebuild.
With a cheap motor, we don't care. If a bearing fails, we're going to throw it away anyway. Also, with something this small, a fuse or breaker most likely will trip before total failure. Fused at 1 amp, it would probably draw 2 Amps or more with a bad bearing.
A 50 HP motor might be fused at 80 Amps, draw about 60 Amps full load, and maybe 65 amps with a bad bearing.