Wire a drum switch to a Teco FM50?

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architard

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This questions is mostly aimed at Ken. I was going to ask it in the thread I had started about my Clausing 4914 but I figured it would be easier for other people to find info specifically about this topic in the appropriate forum.

Like many others I am also electrically challenged. I've now read almost everything on this site about VFDs and still have questions. I came across a thread that had some information about wiring the drum switch on his 4900 to his Teco FM50. However I don't really understand it.

I understand that there will be three wires that I need to hook up to the VFD to get the drum switch to work but where do those wires go to since there are 6 terminals? Are there any wires that need to go from one terminal to another terminal within the drum switch to get that to work?

I have some solid Cat5 cable from work that was being thrown out . Will this work for the low voltage signal wiring? Or should I get something more robust and shielded?

I figured I'd ask Ken since his drum switch will be identical to mine.

Of course this might all be easier with the actual machine and VFD in front of me. I'll have the lathe and VFD in my shop by Sunday. I'm chomping at the bit to get this thing home!
 
Kent, I'm puzzled by the question, a little. If you want the drum switch to handle the reversing, then you shouldn't need it at all. The VFD controls all the motor functions, including direction of rotation.

In general, CAT 5 cable will handle signal level current just fine, and the shielding requirement depends on the sensitivity of the application. I always use shielded when I can though, just because I can. One thing to keep in mind about bulk CAT cabling is that solid is not intended to flex in use. That's why you will see patch cables for computers made from stranded, not solid. Copper work hardens easily, and will break inside the jacket.
 
Kent, Read this thread, I posted pics in there: http://www.hobby-machinist.com/showthread.php/3210-Wiring-reverse-off-forward-switch-to-vfd

Re-cap:
1) Strip high voltage wiring from switch (the VFD is wired directly to the motor)
2) Number all the contacts
3) Using a ohm-meter, map out the switch. Wire down which contact are OPEN or CLOSED at the three different switch positions.
4) Wire low voltage cabling from VFD to appropriate contacts, CAT5 wire is fine but since its has solid conductors it may be prone to breaking from the vibration. But since you have it use it.

Clears as mud? :lmao:
 
Tony Wells said:
Kent, I'm puzzled by the question, a little. If you want the drum switch to handle the reversing, then you shouldn't need it at all. The VFD controls all the motor functions, including direction of rotation.
Click to expand...
He wants to re-wire the drum switch to low voltage to control the VFD remotely.
 
Gotcha. I just see it as dangerous (to the VFD) to put it between the VFD and the motor. No problem doing the f/r wiring to control the VFD.
 
Tony Wells said:
Gotcha. I just see it as dangerous (to the VFD) to put it between the VFD and the motor. No problem doing the f/r wiring to control the VFD.
Click to expand...

that is indeed dangerous to put it between VFD and motor, but what Kenny is suggesting is to connecct the drum switch to the FWD/OFF/REV terminals on the VFD using low-voltage circuit - this is not connected to the motor (motor is connected separately and directly to VFD on the LINE high voltage circuit) so this is quite safe, and in fact what the VFD is designed to do

I can probably draw a diagram of this if necessary. although I'm sure Kenny had it covered in the other thread.
 
Sharon,
I have no problem with doing that. I do wonder though, about the long term effects of using NC contacts in place of momentary contact switches, which is what I have seen on all the VFDs I have used. Never any small ones, just a few between 30 and 200 HP. The controls were all membrane pushbuttons that were momentary contact.
 
Tony Wells said:
Sharon,
I have no problem with doing that. I do wonder though, about the long term effects of using NC contacts in place of momentary contact switches, which is what I have seen on all the VFDs I have used. Never any small ones, just a few between 30 and 200 HP. The controls were all membrane pushbuttons that were momentary contact.
Click to expand...


Tony, I reckon this might be VFD model specific terminal specifications. on the FM50, there are 3 terminal that require a NO/C contacts for the FWD/OFF/REV control of the motor. the VFD relies on these contacts to stay closed for the entire time the motor is supplied with power as opposed to other VFDs that might only requires a momentary electrical signal to signal the controller to send power to the motor or stop it. with the FM50 the rocker switch matches the controllers specifications and requirements and works really well.
 
I admit not having looked at this specific VFD, but if it has rocker switches, then there's absolutely no reason not to sub in a remote 3 way drum switch. Should work just fine.
 
Ken was picking up what I was putting down ;)

I'm a total electronic dolt, but I've at least figured out from reading that you NEVER put anything between the VFD and the motor.

I think I have a multimeter around here somewhere but the battery may be dead. I watched some YouTube videos on reading resistance on a switch so I think I understand now. I take it since you only need 3 contacts for the remote signal wiring to the VFD you simply aren't using all of the original functioning contacts on the drum switch?

Not sure I completely understand the rocker switch stuff. In the FM50 manual it says depending on your F_11 settings the SW1 switch will change the external signal type to either 0~20mA analog, 4~20mA analog or 0~10VDC analog. Which one do I want to set it to to use a drum switch?

I have dozens of cat5 patch cables here at work so I should be able to snag one of them. The solid wire stuff was already in the trash and being a pack rat I fished it out. I'll probably use cat5 just to get things up and running but I'll eventually replace it with something a bit more robust.

I tend to follow the motto of Hunter S. Thompson, "if there is anything worth doing, its worth doing right." Although more often than not he was referring to drug fueled benders, not machinery wiring. :lmao:

That's all the dumb questions I'll ask until I actually get it home. :))
 
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