Sharing a VFD

[Ramper]

I have 2 3-phase drill presses. I only have one hooked up to the VFD. I would like to make a quick connect that I could use the same VFD with BOTH presses. I am thinking that my options are to just hook both up and only use one at a time (only me in the shop) or a way to disconnect one and plug in the other (might be safer if someone else is in my shop). I plan to set one press to high speed (wood) and one to low speed (metal).

I am thinking something like Anderson power poles, but they need to be 120V

 

[Norcal]

Considering how cheap A/C drives are not really a good idea but if you are insistent a couple 3 phase locking attachment plugs for the drill presses and a matching connector for the drive would work, do not under any circumstances use a single phase plug. VFD’s do not tolerate being disconnected under load between the drive and the motor very well which is why I said it’s not a good idea.

 

[rsanter]

You cannot have both always hooked up. You will be turning it on and off with the VFD so it will try to run both of them.

If it was me I would use a 3ph twist lock plug.
One female on the end of the VFD output, and then have two male plugs for each of the DP motors.
Plug in the one you want to use

 

[slow]

Most vfds will not tolerate an open output, so make sure you power down the drive before swapping motors

 

[DSMR]

I have ran 2 motors on one vfd before. You have to supply both motors with individual external overloads to accomplish this the correct way.

If you are going to run only one vfd at a time I would use a reversing contactor and a selector switch with some logic to only allow it to switch contacts if the motor is stopped.

 

[matt_i]

I would just hardwire them both and just use them one-at-a-time as would happen in a 1 man shop.

A drill press is so lightly loaded it would be nearly impossible to use full HP, the belts will almost always slip first if there's a lockdown overload.

Then you eliminate the possibility of doing something stupid with the plugs while the drive is sending energy.

I think you want 300vac rated components probably, while a VFD can have a 120vac x 1 phase input it will typically have a 240vac x 3 phase output.

The logic sounds good but you'd have to have a bit/contact that changes state when the drive is at zero speed ( could be an open-loop timer). That the Start command = 0 is insufficient in my opinion because there could be DC injection braking during the coast-down that potentially wouldn't play well with a hot-switch.

As for start-stop, I'd use a 3 wire control and place the starts in parallel and the stops in series.

 

[Kev In]

If you have 3 phase motors with the same hp, you can use IP67 Aviation 4 pin connectors. I use them on one KBAC 27D VFD and on two 3 phase 1.5 hp motors.

It makes it easy to move equipment, VFD or to control various motors with the same VFD.

You can buy them on Amazon. Make sure you buy the correct amp rating connector for your motor. Always make sure your VFD has a line switch or unplug it before you disconnect the 4 pin connector.

 

[gtcs]

I have set up a similar contraption using a manual transfer switch. I wired the drive to the load (common). Then each of the identical motors on the 2 line.

 

[ddawg16]

Wow....so much mis-information.

VFD's are used all the time to run 2 or more motors. In your case, I'm assuming you only want to run one at a time.

Open inputs? The VFD could give a ****.....in fact, running the VFD open if part of the typical setup of a VFD.

As for connections. My suggestion.....

Have a 3-ph switch/disconnect at each drill press. GTCS's suggestion of a transfer switch is a very good idea. It means you will be running only one drill press at a time.

The Start/Stop for the VFD can be common to both drill presses. The only one that will run will be the one the transfer switch is connected to.

Start/Stop....two types.

1. Momentary Start with momentary Stop
2. Maintained Start with interlock Stopped.

Allen Bradly and a few others make a Start/Stop switch that is perfect for option 2.

 

[mike93lx]

Wow....so much mis-information.

VFD's are used all the time to run 2 or more motors. In your case, I'm assuming you only want to run one at a time.

Open inputs? The VFD could give a ****.....in fact, running the VFD open if part of the typical setup of a VFD.

As for connections. My suggestion.....

Have a 3-ph switch/disconnect at each drill press. GTCS's suggestion of a transfer switch is a very good idea. It means you will be running only one drill press at a time.

The Start/Stop for the VFD can be common to both drill presses. The only one that will run will be the one the transfer switch is connected to.

Start/Stop....two types.

1. Momentary Start with momentary Stop
2. Maintained Start with interlock Stopped.

Allen Bradly and a few others make a Start/Stop switch that is perfect for option 2.

IMO, getting into transfer switches and non-standard start/stop gear, I would buy a second vfd. Especially if the motors will be run differently

 

[Falcon67]

If the controls are the same on both DPs then should be no problem. If not, your complications will be in the control wiring and not the motor power. VFD supplies power to the motor directly and not like 3 phase utility power, so you could technically run the VFD motor feed to a outlet and just plug in the unit you want to use and turn on the VFD. Control switches wired in parallel should not be an issue if it's the same signalling on both machines - V-stop, run, jog, rotation, etc.

Agree - if the controls are different, just buy two VFDs.

 

[slow]

https://www.schneider-electric.us/en/faqs/FA173243/

For the open VFD output details. Yes, a disconnect is often installed after the drive for serving the motors, but they don't like being opened/closed under motor power

 

[ddawg16]

https://www.schneider-electric.us/en/faqs/FA173243/

For the open VFD output details. Yes, a disconnect is often installed after the drive for serving the motors, but they don't like being opened/closed under motor power

Agree.....it's a 'best practice' to not open and close the output with a switch. It messes with Accel/Decel functions of the VFD. It won't break it....but it's not a 'suggested' practice.

 

[mm08822]

https://www.schneider-electric.us/en/faqs/FA173243/

For the open VFD output details. Yes, a disconnect is often installed after the drive for serving the motors, but they don't like being opened/closed under motor power

The best way to protect a vfd from opening under load, be it a disconnect or plug/receptacle is to have an interlock circuit built in at the disconnecting point.

In a disconnect, having an early break/late make aux contact on the disconnect handle works.

For a receptacle, an early break/late make pair of aux contacts is provided in the recept. The plug contains a jumper to complete the circuit of the aux contacts. Downside of this is a 6 conductor cord is required on the recept side.

In either case, the aux contact kills the drive enable before the output circuit is opened.

 

[mm08822]

• Unless the two motors have the same FLA’s one of the motors will not have the proper values set for o/l in the drive. (And no one will change them.)
• Adding O/L relay hardware is an unneeded complexity and cost.
• Having 2 sets of start/stops hooked between 2 drill presses is unnecessary (PIA) tethering of equipment.
• Adding a plug/receptacle on the vfd output requires it to be hp rated at the proper voltage.
• Opening (or the possibility) of the plug/recept underload is still possible.
• A xfer sw has the same problem.
• Interlock hardware is just more complexity/cost.

Simplest way is to mount a vfd to the side of the dp.

• Provide a corded 240vac plug to it.
• Hard-wire the motor to vfd.
• Set the o/l protection, min/max speeds, ramp rates for the dp.
• Decide if you want to use the vfd start/stop pb’s or put a hardened stop/start station where best suited for user access/safety.
• Use a 3wire control (momentary pb’s) not a 2 wire control for added safety.
• Everything is self-contained on the drill press and straight forward.
• No booby-traps waiting to spring later.

Do the same for dp #2. Can’t be any simpler.

 

[MattT]

• Unless the two motors have the same FLA’s one of the motors will not have the proper values set for o/l in the drive. (And no one will change them.)

• 
  
  Many drives will support two parameter sets. Just put an aux contact/switch on whatever is used to change between motors and the drive will switch parameters automagically. So that part is do-able so long as the motors are fairly close in size.
  
  Though unless the drill presses have fairly large motors the project is more trouble than it's worth.

 

[mm08822]

Many drives will support two parameter sets. Just put an aux contact/switch on whatever is used to change between motors and the drive will switch parameters automagically. So that part is do-able so long as the motors are fairly close in size.

Though unless the drill presses have fairly large motors the project is more trouble than it's worth.

Can't say I've ever seen (nor ever looked) for multiple motor settings wrt o/l protection within . Speed sp's, accels, decels, sure, but o/l, min, max?

But again, another s/s, tethered dp's, etc.............

Who's making a drive with multiple o/l settings or is that what you infer with "close in size"??

 

[ClappedOutBport]

Wow....so much mis-information.

VFD's are used all the time to run 2 or more motors. In your case, I'm assuming you only want to run one at a time.

Open inputs? The VFD could give a ****.....in fact, running the VFD open if part of the typical setup of a VFD.

As for connections. My suggestion.....

Have a 3-ph switch/disconnect at each drill press. GTCS's suggestion of a transfer switch is a very good idea. It means you will be running only one drill press at a time.

The Start/Stop for the VFD can be common to both drill presses. The only one that will run will be the one the transfer switch is connected to.

Start/Stop....two types.

1. Momentary Start with momentary Stop
2. Maintained Start with interlock Stopped.

Allen Bradly and a few others make a Start/Stop switch that is perfect for option 2.

Quoted for truth!

My dad uses a 5hp VFD to run his entire machine shop. That means: starting and stopping machines with drum switches, instant reversing machines, having opens with nothing running, running two or three machines at once, etc, etc. The only time it's every caused a problem was back when he used a 1hp VFD and started a bit too hard starting of a 1hp motor and burnt it up. Now he uses a 5hp. I won't recommend doing things this way, I'd rather have a RPC but you CAN.

So, drum switches, plugs, basically anything but a magnetic starter will work fine. And if you forget to turn one off or unplug it, both will start spinning when the VFD starts. NBD

 

[alfredeneuman]

Quoted for truth! .... So, drum switches, plugs, basically anything but a magnetic starter will work fine.

ANY switch between the VFD and the motor will greatly reduce the life of the VFD.
They do permanent damage the output transistors a little bit every time they're used and over time will cause the VFD to fail

The only switches that should be between the VFD and the motor are emergency stops

 

[DSMR]

I would do it something like this (I apologize for the handwriting):

I would use the reversing contactor as it is cheap and mechanically linked.

Surely your VFD can be programmed to send out a "Motor Stopped" signal. If not, throw it away!

So a relay, a contactor, a selector switch, and you have a very clean "dummy proof" way to control both motors without having to think about much and you can mount the Selector switch (3 Pos would be good, [X00] For DP1, [00X] For DP2, [0X0] For Off) somewhere convenient.

Also, there are many ways to accomplish what you want, this is just the way that I would do it. So food for thought.

 

[laser3kw]

Can't say I've ever seen (nor ever looked) for multiple motor settings wrt o/l protection within . Speed sp's, accels, decels, sure, but o/l, min, max?

We use Yaskawa V1000 and they have that function