Multiple machines on VFD

[chris kenney]

OK--I have a Oliver 159A and Powermatic Model 10 mortiser, both 3 phase machines, wired up to Lenze SMV VFD'S in my shop. The VFD'S are hard wired into the breaker box. The VFD'S are also then wired to a wall plug. Both of my machines have the appropriate plug and are plugged into the wall mount plug. The machines run great. The VFD'S are sized appropriately re: horsepower. My question is this. I just acquired a MAX spindle sander for restoration. It has a Baldor 3 phase 1 HP motor (220). Not sure what the former configuration was but all it has now is wiring into an off/on control box. Can I just have the motor wired up with plug and "share" the plug for the Powermatic machine? Would seem more economical than buying another VFD and installing new wiring to box and new wall plug. PS--I have not gotten around to programming the particular VFD to each machine--I could see where this could be an issue trying to run 2 machines off I plug--or would it?







Thx
Chris

Atlanta, GA

[Allan Speers]

You could try it, but I wouldn't.

VFD manufacturers say to use one VFD per machine. I think they sense amperage,or something, so there's an important feedback loop going on. Even without vari-speed, they act as a sort of heater, protecting the motor if it overheats.

You could try calling FactoryMation. They have very good tech support.

[David Kumm]

Would you only keep one machine plugged into the vfd at a time? If the motors are similar in size and amperage and only one runs, there is no terrible downside. If the parameters of the motors are different it will be a pain to reprogram each time but if they are similar, you are OK. I keep a couple vfds on a board with a french cleat and use them as auxiliary units for machines that are seldom used. Dave

[Malcolm McLeod]

Would you only keep one machine plugged into the vfd at a time? If the motors are similar in size and amperage and only one runs, there is no terrible downside. If the parameters of the motors are different it will be a pain to reprogram each time but if they are similar, you are OK. I keep a couple vfds on a board with a french cleat and use them as auxiliary units for machines that are seldom used. Dave

Specs on the motors are the key. As David says, if any 2 motors are (virtually) identical in horsepower and amperage, then you could connect them to the same VFD. If they are different, then something has to compromise. You could set the VFD for the higher amp motor, but then the 'smaller' amp motor has somewhat less protection - or you need to change the current limit parameters to match the motor every time. (Chris, you'll have to decide on your risk tolerance.)

As many have alluded to in other threads, most VFD's have amazingly complex configurations and operating possibilities. In the context of this forum 90% of the parameters are nearly useless, but they are still there. I've always used dedicated VFDs - so never tried this, but some VFDs could probably be set to use 2 or more motor configurations - selected by a switched input to the VFD. If so, you could use a compound plug/receptacle to connect a given machine to the VFD. The connection could transfer power, connect the machines start/stop switches, and 'tell' the VFD which operating parameters to use. (I know this is getting pretty sophisticated for the average woodworker, but if you like to reach it might be intriguing?)

Only other caution is NEVER unplug one motor and plug in the other with the VFD powered up - even if it is stopped. And like other threads have emphasized, remove the start/stop switches and/or mag starters from between the VFD<>motor. Always kill the input power to the VFD before disconnecting any motor.

For the Rube Goldbergs out there, you can simultaneously operate multiple motors off the same properly sized VFD. Each motor will run at the same speed, and each needs its own specific overload protection, and if one trips, it must shut down all the others. But other than these small inconveniences, nearly anything is possible...:cool:

[Matt Day]

I have a VFD I wired up to use with multiple machines. I have one plug for the remote switch (standard 120 plug), and one plug for power (220 plug so they can’t be mixed up). I usually have my buffer/grinder hooked up to it, but can also use my spindle sander, and hopefully a disc sander when I find one.

Change a couple plugs and the machine is ready to go. Of course it might not be the most convenient but it works and is a lot cheaper than a vfd per machine.

For the Table Saw and planer and bandsaw, I use them enough to warrant a VFD per machine.

[Terry Therneau]

I also have a VFD wired for two machines, and use 2 plugs in the same way as Matt. The setup of the VFD is for the 1.5 HP shaper, but I don't use the shaper that often. Most of the time the VFD is plugged into my 6" jointer (Yates, direct drive, 1920s vintage, .5 HP). It is true that I get no motor protection on the jointer, but an overload is not an issue there. The edge sander and tablesaw are on their own VFDs, since I go back and forth to these all the time.

Terry

[Chris Hachet]

I am setting up something similar using two contactors with auxiliary contacts for a friend. that way each machine can have an off/on start stop switch and I can make sure the other machine will not be energized. Using a selector switch to make sure only one contactor is energized at a time.

[Bill Dufour]

All power switching needs to be done with the vfd not at the machine. Different machines may want some different parameters such as reverse lock out and acceleration/deceleration times. If machine shave same horsepower and times can be the same it will work fine. But where will the low voltage switches be so it is convenient to all machines?

[Bill Space]

Can’t help but think as soon as you forget and make some simple error that causes one of your VFDs to fail, you will regret not buying a third VFD to begin with.

Thay are not that expensive.

This comment is based on knowing what I am capable of, and I assume we are at least equals! :D

[Matt Day]

My switches have their own plug, so the on/off switch goes with the machine.