3ph and VFD's

[DaveTTC]

I have a number of 3ph machines but have moved to where 3ph is not available.

My understanding is a 1ph to 3 ph vfd is some kind of motor that has to be switched with your old motor?

I have about 12 machines running (if they were set up) on 3ph. The biggest motor is likely the 24" planer / thicknesser.

What are my options baring in mind finances are rather tight.

Dave TTC
Turning Wood Into Art

[NCArcher]

Not quite Dave. A VFD is connected in between your power supply and your existing motor. The single phase to three phase VFDs are fairly economical up to about 5 kW but you need one for each motor. They range from around $180 to $700 depending on the size of the motor and what it is doing. You also need to ensure that you have all 6 wires at the motor terminal box(delta connected) to connect the VFD to. If you only have 3 wires at the motor terminal box (star connected) you will need to have the motor modified by a motor rewinder before you can run it from single phase via the VFD. (You can run it while it is still star connected but you will be limited to approx half the rated HP of the motor)
Someone linked some good explanations of VFDs recently but I can't remember which thread it was in.

[DaveTTC]

Is it possible to wire a vfd to all the motors and just have a switch for which one you want to use?

Dave TTC
Turning Wood Into Art

[BobL]

I have a number of 3ph machines but have moved to where 3ph is not available.

DANG!

My understanding is a 1ph to 3 ph vfd is some kind of motor that has to be switched with your old motor?

You are thinking of an RPC (Rotary Phase converter)

A VFD is a box of rapid electronic switches about the size of half an upright loaf of bread that makes 3P from single phase.
Even a basic VFD does a lot more than make 3 phase - its a programmable box that at a minimum allows for speed control across a limited range.
Usually each machine usually has its own dedicated VFD to suit that motor and cost ~$140 for a basic/basic VFD for a small machines, to $3-500 for bigger machines.

Most users add VFDs for more than just 3P capability so unless you required these other capabilities on the 12 machines the cost will be significant.

Just purchasing a VFD is not the end of the $ trail
The motors have to be be able to run on 240V 3P - not many do that so they many have to be converted and that will cost around $100
In addition it sounds like you are not in the DIY VFD category so you will have to get a sparky to install these.
Unless you get lucky finding a sparky to do this is difficult. Then the sparky may not want to be installing budget/basic VFDs (he/she after all does not want to be called back if they break down) and may only want to install better quality units - for better quality units expect to double the price.

I have about 12 machines running (if they were set up) on 3ph. The biggest motor is likely the 24" planer / thicknesser.

It sounds like an RPC might be your best bet cost wise.
Many RPC setups are DIY but it sounds like you are not in the DIY RPC category so you are best off talking to your sparky.

[BobL]

Is it possible to wire a vfd to all the motors and just have a switch for which one you want to use?

Dave TTC
Turning Wood Into Art

It is but it is not advisable for different sizes/types motors.
VFDs are specifically programmed to suit each motor so unless you are prepared to reprogram the VFD every time you switch the motor it's not worth doing.

Even if the motors are identical it is not always as simple as it sounds like it might be.
I'm going through the throes of setting up identical two grinders to be alternately able to run off one VFD and it has been a RRPITA (Right royal pain in the A) and it is unlikely that I will repeat that exercise in the future.

It will probably bamboozle you but if you are interested have a look at this https://www.woodworkforums.com/f65/gmfs-vfd-196127

[DaveTTC]

Thanks Bob. Now I'll twiddle my thumbs while I await a reply firther reply to that thread

Very interesting thread. Thankyou

Dave TTC
Turning Wood Into Art

[Ed..]

I currently run two different machines off the one VFD, I have a 3phs 3KW wood lathe and a 3 phs 3Kw 14" table saw, The way I did it was make up a small portable switchboard with a isolating main switch, emergency stop button, 10A circuit breaker as well as the VFD and a 5 pin plug to get power from my extension lead, I have another 5 pin plug that goes out of the VFD to connect to either machine, so when ever I want to run the table saw I just unplug the wood lathe and just connect it to the saw. This way I can run either motor and they are protected with a 10A circuit breaker. The extension lead I use to power it all up is protected by a 32A circuit breaker which would not protect the small 3Kw motors and I use it mainly for powering up my big welders, but when needed I just connect the lead to the switchboard and then to either the saw or the wood lathe. The VFD is rated to 4Kw so I could also connect a larger motor as well. The programming of the VFD was definitly the job for my sparky mate. I originally wanted to put in a magnetic contactor to the emergency stop switch but my sparky friend advised against this as hitting the emergency stop switch in the event something went wrong would stop powering the VFD's braking feature, which is what I needed in case I wanted the wood lathe or the saw to stop quickly. Hope this makes sense.

[BobL]

I currently run two different machines off the one VFD, I have a 3phs 3KW wood lathe and a 3 phs 3Kw 14" table saw, The way I did it was make up a small portable switchboard with a isolating main switch, emergency stop button, 10A circuit breaker as well as the VFD and a 5 pin plug to get power from my extension lead, I have another 5 pin plug that goes out of the VFD to connect to either machine, so when ever I want to run the table saw I just unplug the wood lathe and just connect it to the saw. This way I can run either motor and they are protected with a 10A circuit breaker. The extension lead I use to power it all up is protected by a 32A circuit breaker which would not protect the small 3Kw motors and I use it mainly for powering up my big welders, but when needed I just connect the lead to the switchboard and then to either the saw or the wood lathe. .

I would not recommend this method as being reliable enough as it requires an operator to turn off a motor before the plug is removed.
Removing the plug with the motor running risks damage to the VFD.

It's not clear where the 10A breaker is but I hope it's not between the VFD and the motor because this would be the same as pulling the plug with the motor running
Breakers don't usually help with this problem as all the dangers are related to the energy stored inside the VFD whether is power is connected or not

Hence a physical lockout should be used on the plug so it cannot be removed while the motor is on.

If you want to see a fully locked out system that runs two machines off one VFD have a look at this thread. https://www.woodworkforums.com/f65/gmfs-vfd-196127
A setup with a cross over switch is also easier and safer than continually removing an inserting plugs which should be kept to a minimum

My other concern is a table saw and a lathe combination also wont utilise a VFD very efficiently.
The table saw is almost certainly has a 2850 RPM motor while the lathe is probably a 1440 RPM motor.
This means the lathe can easily use frequencies up to 120Hz (hence minimise belt changes) but this should not be done on the table saw if it does have a 2850 RPM motor.

[Ed..]

BobL;

]I would not recommend this method as being reliable enough as it requires an operator to turn off a motor before the plug is removed.
Removing the plug with the motor running risks damage to the VFD.

It's not clear where the 10A breaker is but I hope it's not between the VFD and the motor because this would be the same as pulling the plug with the motor running
Breakers don't usually help with this problem as all the dangers are related to the energy stored inside the VFD whether is power is connected or not

The main isolating switch is first followed by the circuit breaker followed by the VFD and I think that the emergency stop is connected to one of the VFD circuits designed for that purpose.

Hence a physical lockout should be used on the plug so it cannot be removed while the motor is on.

I am the only user of these machines so no one else can pull the plug when the machines are running and it is not something I would even attempt to do when a saw is running.

If you want to see a fully locked out system that runs two machines off one VFD have a look at this thread. https://www.woodworkforums.com/f65/gmfs-vfd-196127
A setup with a cross over switch is also easier and safer than continually removing an inserting plugs which should be kept to a minimum

My other concern is a table saw and a lathe combination also wont utilise a VFD very efficiently.
The table saw is almost certainly has a 2850 RPM motor while the lathe is probably a 1440 RPM motor.

That is correct on the RPMs on the respective machines. The wood lathe has only a double set of belt steps so I can rev it up to over 2000 RPM or else reduce the speed by using the smaller ratio pulley and have about 1200 rpms at low speed and variable within those ranges by the VFD. However I mainly use the lower speeds as that lathe was designed for large logs/bowls, (I can spin a 1m thick log). The Table saw spins at 4060RPM. By using the VFD it gives me the emergency braking and amp overload functions.

This means the lathe can easily use frequencies up to 120Hz (hence minimise belt changes) but this should not be done on the table saw if it does have a 2850 RPM motor.

The VFD is not programmed to use the higher frequency as the 4060RPM no load speed is a tad too fast anyway, one of these days when I have time I will take the pulleys off the table saw and machine them down to give me about 3000RPM and more torque. I have used it to rip 120mm thick lemon scented gum tree slabs for several hours at a time but I did think the motor was getting a bit too warm for my liking after that time, although it was still within the specs for that motor. I kept an eye on the temps with my IR meter to make sure. https://www.youtube.com/watch?v=64e4yb9xEk8

Cheers

Ed.

[BobL]

The main isolating switch is first followed by the circuit breaker followed by the VFD and I think that the emergency stop is connected to one of the VFD circuits designed for that purpose.

I can understand why this was done nut the breaker is a bit redundant as the VFD should be able to act as its own current limiting device.

Hence a physical lockout should be used on the plug so it cannot be removed while the motor is on.
I am the only user of these machines so no one else can pull the plug when the machines are running and it is not something I would even attempt to do when a saw is running.

I'm pleased you can trust yourself, I could not do that - it only takes a moment of inattention or a distraction and I would forget. This usually happens when I'm in a hurry.

My other concern is a table saw and a lathe combination also wont utilise a VFD very efficiently.
The table saw is almost certainly has a 2850 RPM motor while the lathe is probably a 1440 RPM motor.

That is correct on the RPMs on the respective machines. The wood lathe has only a double set of belt steps so I can rev it up to over 2000 RPM or else reduce the speed by using the smaller ratio pulley and have about 1200 rpms at low speed and variable within those ranges by the VFD. However I mainly use the lower speeds as that lathe was designed for large logs/bowls, (I can spin a 1m thick log). The Table saw spins at 4060RPM. By using the VFD it gives me the emergency braking and amp overload functions.

What VFD frequency range are you operating over?

The VFD is not programmed to use the higher frequency as the 4060RPM no load speed is a tad too fast anyway, one of these days when I have time I will take the pulleys off the table saw and machine them down to give me about 3000RPM and more torque.

Do you mean the blade is running at 4060 or the motor is running at 4060 rpm?

If you are cutting 120 mm depths at full speed you obviously have oodles of torque so why not just reduce the frequency of the VFD output? What sort of VFD is it - do you know if it is a vector Drive VFD - if so this could be setup to have close to the same torque even at lower revs which would help with your table saw issue

I have used it to rip 120mm thick lemon scented gum tree slabs for several hours at a time but I did think the motor was getting a bit too warm for my liking after that time, although it was still within the specs for that motor. I kept an eye on the temps with my IR meter to make sure. https://www.youtube.com/watch?v=64e4yb9xEk8

That's good to hear, I include panel meters that show the current draw by the VFD on my heavier draw powered devices this tells me how close I am to tripping so I can ease off things if I need to.

[Ed..]

Hi BobL, the VFD is an EMHeater EM9-G3-004 and I assume that my sparky just set it up to go to 50hz, at least that is what it displays on the keypad. I have added a page scan of the features of it from the manual. I hope it makes more sense to you than me. As far as I can tell it can go up to 600hz.

The motor runs at 2850 RPM and is stepped up via a pulley to the 4060RPM, I would prefer more torque for the lathe as at low speed it looses a lot, I will have to get the sparky back to do it though. The table saw just needs a little bit more for slabbing the Iron Bark that I do occasionally but as I said before I will reduce the size of the pulley to do that.

It is a bit hard to not notice that the saw is running as it howls and the 2HP dust extractor is also right next to it, it is quite hard to pull out a 3 phase plug so can't just do it on the spur of the moment. I originally built the powerboard just for the lathe, but since I have it, I figured why not use it on all the machines for a bit of extra protection, as 3 of my powerpoints are all protected by 32A C/breakers and the last one is a 20A for the metal lathe. When I cut plywood and small timber I do occasionally plug it direct to my lead and mainly use the VFD only when slabbing the 120mm+ thick timber as that is probably where a problem might develop. Having the powerboard with the VFD on it I can just connect it to whichever machine I want.

[BobL]

Hi BobL, the VFD is an EMHeater EM9-G3-004 and I assume that my sparky just set it up to go to 50hz, at least that is what it displays on the keypad. I have added a page scan of the features of it from the manual. I hope it makes more sense to you than me. As far as I can tell it can go up to 600hz.

OK that VFD has sensorless vector control which means it can generate lots more torque at lower speeds than a frequency controlled VFD.
If the sparky has not enabled this feature (Its not usually automatically enabled) I recommend you get it enabled because it increases the available torque down to lower revs. I only have one of these VFDs (one the metal work lathe) and I really like it.

The motor runs at 2850 RPM and is stepped up via a pulley to the 4060RPM, I would prefer more torque for the lathe as at low speed it looses a lot, I will have to get the sparky back to do it though. The table saw just needs a little bit more for slabbing the Iron Bark that I do occasionally but as I said before I will reduce the size of the pulley to do that.

See comment above.

It is a bit hard to not notice that the saw is running as it howls and the 2HP dust extractor is also right next to it, it is quite hard to pull out a 3 phase plug so can't just do it on the spur of the moment. I originally built the powerboard just for the lathe, but since I have it, I figured why not use it on all the machines for a bit of extra protection, as 3 of my powerpoints are all protected by 32A C/breakers and the last one is a 20A for the metal lathe. When I cut plywood and small timber I do occasionally plug it direct to my lead and mainly use the VFD only when slabbing the 120mm+ thick timber as that is probably where a problem might develop. Having the powerboard with the VFD on it I can just connect it to whichever machine I want.

Are you at least able to keep the VFD plugged in and turned on while you switch between machines? If not having to repeatedly power down/up the VFD so it can be moved is not good for the VFD.

I agree about noticing the saw is running - might not be so easy to note the lathe or other machine is running especially if nothing is on the headstock although that would obviously be rare. I'm more concerned about folks not knowing about this potential problems and then turning around and using it in a multi user environment which is when things seem to go wrong more often.

In my shed I have 10 machines and 9 VFDs.
I can fine tune the VFDs specifically for each machine e.g. can the use the full frequency range of the motor/machine. One thing I found out is that different machines handle acceleration and deceleration differently e.g. grinders cannot cope with any rapid deceleration unless you like the idea of a spinning wheel bouncing around the workshop and/or damaging the VFD.
I find swapping one VFD between the 2 grinders OK because there is no plugging and unplugging, just flipping a cross over switch - and because they are identical grinders the VFD parameters suit both machines.

When I'm working I also like to have several machines quickly available at the same time so its not unusual for my metal work lathe, DP, grinders, and compressor to all have their VFDs switched on and ready to run. I would find it very irritating to switch the VFD every time I needed to use a machine as the stop and start up time would drive me nuts.

I also have a 10th VFD. This one is 3P-3P 7.5HP and is like yours in a box with plugs etc. This is my testing VFD for gear at the mens shed and only I get to use it.

[Ed..]

Hi BobL, One day I will get my friend to come over and set it up differently, but at the moment I am not to concerned as I have too many things on the go at the moment, as for the VFD, it is always shut down down before I change it over to the other machine as I don't use either of the machines much at the moment. I have a couple of wood projects in mind before X'mas so trying to get all the machinery organised before I start. I am in the process of welding up a 200l pressure cooker and after that I will go back to building a 60cm drum sander, followed by a radial arm saw/grinder which I started about 18 months ago before I developed health problems. Too many projects and too little time to do them in.

Incidently that drum sander will be bolted to the wood lathe bed and spun by belt off a pulley on the spindle. As the wood lathe weighs about 450Kg it's mass should stop any vibrations, and also save me getting another motor . The low speed of the lathe is more than fast enough for a drum sander. Once I get the drum sander and the radial arm finished, my workshop will be pretty much complete and so I can get stuck into the 3 cubic meters of timber I have taking up space on the garage floor for the last couple of years waiting for it to dry.

I do have a very healthy respect for powered machines so everything gets switched off before any thing is changed especially my metal lathe, I have seen a pic of a guy who got grabbed by a slightly smaller one than mine, that sort of image stays with you forever. You don't get a chance to say Ooops ... shouldn't have done that, by then it's too late!

Anyway that is why I have just the one VFD as it can run several motors and I can only run one machine at the same time, keeps me focused on what I am doing so less chance of having a "senior moment" or a Oooops moment! if you know what I mean. I will put up with the inconvenience!

Cheers

Ed.