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Motor Starter For A Reversing Motor


ypl4

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I have put together a fairly inexpensive 1/3phase reversing motor controller, but now I have a few code/UL questions:

 

-I have a 40VA class 2 transformer to power a small logic circuit (manual/remote operation, hand controls, time delay, electronic interlock, 2 sets of safety limit switches, etc. etc.) I know I don't have to fuse the secondary because my transformer is inherrently limiting, but do I have to fuse the primary?

 

-If so, what kind of fuse can I use? (ok my question really is can I use one of those midget fuses? or do I have to go with the larger and more expensive CC fuses? Seems a bit of an overkill for a tapped circuit.)

 

-The other question is the interlocking of the forward/reverse contactors. I have the circuit to electronically interlock the drive to the 2 contactors. Do I still need a mechanical interlock on top of that? (UL508A section 33.4.1) Does my PCB now have to be UL qualified?

 

-Please help if you can. Much is appreciated!

 

Once I get these issues resolved, does anyone interested in buying some? My friends here get the friends and family discount :)

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I have put together a fairly inexpensive 1/3phase reversing motor controller, but now I have a few code/UL questions:

Fairly inexpensive is a relative term. Reversing starters in and of themselves are nothing revolutionary. Not sure what you mean by 1/3phase however. Maybe you could elaborate.

 

-I have a 40VA class 2 transformer to power a small logic circuit (manual/remote operation, hand controls, time delay, electronic interlock, 2 sets of safety limit switches, etc. etc.) I know I don't have to fuse the secondary because my transformer is inherently limiting, but do I have to fuse the primary?
Per UL you must fuse one side or the other, but per the NEC both sides will need to be fused by whomever installs it, so the general rule is to just fuse both sides now.

 

-If so, what kind of fuse can I use? (ok my question really is can I use one of those midget fuses? or do I have to go with the larger and more expensive CC fuses? Seems a bit of an overkill for a tapped circuit.)
Don't know what you mean by a "tapped circuit". Fuse class has to do with voltage and interrupting capacity at the available fault current. Your overall starter will need to have an SCCR rating now (since 2005 NEC) and one of the ways to get a higher rating will be to use high interrupting capacity current limiting fuses on the primary side, i.e. Class CC. But you never discussed voltage, so it's impossible to make a determination anyway.

 

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The other question is the interlocking of the forward/reverse contactors. I have the circuit to electronically interlock the drive to the 2 contactors. Do I still need a mechanical interlock on top of that? (UL508A section 33.4.1) Does my PCB now have to be UL qualified?
If you want to UL list your controller, you need to follow all UL requirements. Conventional reversing starters are required to be mechanically interlocked, electrical interlocking is what is optional. Doesn't matter much though, most users will want to see both even if not specifically required. As to the PCB, what PCB? Why do you need a PCB for reversing a motor? It's not that dificult. But if you have a PCB and you want UL on the entire assembly, you will need UL to evaluate all of the components, including any PCB.

 

-Please help if you can. Much is appreciated!
Don't know if that helped much, but it's the truth.

 

Once I get these issues resolved, does anyone interested in buying some? My friends here get the friends and family discount :)

Again, reversing starters are very very common. Besides, discounted from what?

 

"He's not dead, he's just pinin' for the fjords!"
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