Tips/Techniques Motor Conversion question

[Dabbler]

Is the drum switch switching the line out from the VFD, or just wired to the VFD's low voltage forward/reverse control?

I hope it is the latter. You should not have any switches wired between the VFD and the motor. Voids Teco's warranty, etc.

 

[thestelster]

@Susquatch @Mcgyver @Dabbler

Hooked up to the VFD low voltage.

 

[Dabbler]

I can see the conveience of just 'flipping the lever' to reverse! well done!

 

[thestelster]

I can see the conveience of just 'flipping the lever' to reverse! well done!

Yeah, the thought of using those tiny run/stop buttons on the VFD was a definite no-go. Even the start/stop on my surface grinder is unnatural to me. A toggle switch or push/pull switch seems more intuitive.

 

[Susquatch]

Yeah, the thought of using those tiny run/stop buttons on the VFD was a definite no-go. Even the start/stop on my surface grinder is unnatural to me. A toggle switch or push/pull switch seems more intuitive.

I never had any intention of doing anything else. My BIG lathe FWD/REV/NEUTRAL handle will be wired to the VFD.

What threw me off was you describing it as a "DRUM" switch.

I suppose it depends on your original wiring. I my case, I got lucky. My FWD/REV lever is already wired to a simple SPDT switch with neutral that can be wired directly to my VFD. I had been worried about that when I first started looking at the wiring cuz there is no way I wanted to lose that lever. I plan to disconnect it from the two contactors and wire it directly into my VFD.

On the other hand, my mill is wired to a small delicate little switch..... THAT I HATE! I'll change it the same day I run across a better switch for it.

Question - why did you leave the existing drum switch there? I would have been inclined to remove it to avoid any chance of someone using it!

 

[thestelster]

Question - why did you leave the existing drum switch there? I would have been inclined to remove it to a

Which switch, the lathe or the mill?

 

[Susquatch]

Even the start/stop on my surface grinder is unnatural to me. A toggle switch or push/pull switch seems more intuitive.

On the flip side, a surface grinder doesn't need a reverse so just about any kind of switch will work. I have a big green recessed button to turn mine on and an even bigger red one to turn it off.

 

[Susquatch]

Which switch, the lathe or the mill?

Looked like it was on your mill.

 

[Susquatch]

I think I see the answer. The wire going to it is the clue. It's a small wire so it isn't carrying motor current. You basically rewired a drum switch to act like a SPDT with neutral.

So there is no risk.

Nice job!

If I didn't swap my motor to a new one, I could have used my old drum switch that way too.

 

[thestelster]

Looked like it was on your mill.

View attachment 38074

Yes, my mill, but it's 73" off the ground and 18" behind the front. So no one will inadvertently switch it on, unless a susquatch is playing tricks on me

On my lathe, I always put the gears into neutral when I'm not actually using it, so even if it's switched on, no harm done.

 

[thestelster]

I think I see the answer. The wire going to it is the clue. It's a small wire so it isn't carrying motor current. You basically rewired a drum switch to act like a SPDT with neutral.

So there is no risk.

Nice job!

If I didn't swap my motor to a new one, I could have used my old drum switch that way too.

Yup.

 

[Susquatch]

Sorry for all the confusion there @Mcgyver.

Hopefully you have your answer though. Unless you get some off brand VFD that doesn't allow it, you can simply flip the VFD direction switch to fwrd or rev at will and Bob is your uncle.

 

[Susquatch]

@Mcgyver - I should also add here that the appropriate braking resistor can significantly reduce the time it takes to change direction if you need that.

I've stayed on the conservative side of this balance because I don't power tap. It's nice to have the option though.

 

[YotaBota]

Here's my VFD test wiring showing the "drum" switch (bottom right) connected to the VFD. You need to meter the switch for ground, fwd and rev then wire to the VFD accordingly. Works perfectly.