One VFD for both lathe and mill

martik777

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I never use both at the same time so why bother buying another VFD. What type of switch could I used to switch the 3 wires from the lathe to the mill?
 
I know you've heard all the warnings about that but if you are going to do it, the switch just needs to be rated for the current, and you must not switch it when the vfd is on. also, you may need different settings in the unit for each motor
A three pole double throw drum switch is what you want, a hefty one
 
Certainly the latter and possibly both if the unit can "sense" the absence of a proper impedance on the output
You want to have the vfd located between the two machines to mimimize the length of wiring to each motor.
I'm sure other members will chime in and tell you not to do it, so good luck if you do
(that switch you showed is only 2 pole I believe-- don't buy a switch without seeing the internal diagram)
 
The VFD has a bunch of configurable options for a particular motor. I think it would be fortuitous if your lathe and mill needed exactly the same settings. Perhaps it would not make enough difference to be a big issue, but you’d be on your own to figure that out.
 
Thanks, they are almost identical in HP with a base 60hz speed of ~700RPM which gives me a usable torque range of 200-1200RPM with 18-120hz

I don't use many settings, just fwd/rev and a max frequency threshold
 
I believe that switch is for fwd/off/rev, or high/off/low. You would want a switch with 9 terminals, 3 input, and 3 outputs for each motor.

Keep in mind, you do not want to use the factory on/off switches with a VFD, unless you have them wired to the VFD, to power the VFD. Trying to get all that wired up, and also be able to switch which motor they are using, will be a sanity check. Unless you are going to use the controls on the front of the VFD each time.

I seriously gave the same thing a lot of thought. I have a four head Fosdick drill press. Basically a humungus stand, and four individual identical drill presses. After a lot of thought, I went with 4 VFDs. It would not have been that hard, as all the motors are the same, and the controls at the front, But the switching, and possibility of the switches being turned, made the decision for me. Also, afraid of a accident by turning the VFD on, and it is niot switched to the drill press I am thinking it is.
 
Looks like you want a switch with 12 terminals like one of these:
You would need to add 3 jumper wires, for example 2-3, 6-7, and 10-11 to create the 3 switching poles from the VFD, then motor A would connect to 1, 5, and 9 and motor B would connect to 4, 8, and 12
rotarysw12tblu.jpg
rotarysw12term.jpg
 
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