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One VFD for more than one machine...

michael.kitko

Cast Iron
Joined
Oct 30, 2012
Location
Pontefract, UK
Long story short, I am moving overseas and taking my equipment with me. I've been using my RPC to power a panel that is wired to all of my equipment. As it turns out, that isn't a viable option due to the starting surge I have when I start it, so I am looking at a short term solution.

So my question, and I can't find any information on it and I'm not experienced in VFDs at all, can you use one VFD to power one machine, unplug it and then plug in another and run that machine off of it also? I would of course use the VFD to start and stop them, but the part I'm confused about is, they say each VFD has to be programmed individually. Also, if I do have to reprogram it each time, do they make a VFD that has a memory built in for each different machine?

Thank you in advance.

P.S. I am going to a 50hz country and all of my machines are 50/60 except my radial arm saw.

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I'm moving to Pontefract UK. We own a house over there and I'm pretty sure it's an old 50amp service to the house. This is just temporary as I am intending on opening a shop over in Castleford area.

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Y'all don't do things half-way, do yah?

Besides.. anything as don't run proper-like will probably get nicked, sooner, if not later...

:)

I had to laugh at the nicked comment. I've actually said that as a comment to my wife when we talked about going versus not going.

What do you mean by doing things halfway? You referring to Canadians?

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Short answer to the original question, for the most part a VFD is not a plug and play power source that can be used for different machines. In some cases, if the VFD is sufficiently oversized, it might be able to be used in this application but will not play nice with transformers and electronics, as it is PWM three phase and not true 3 phase. In most cases they are directly wired to the motor, no contactors, overload relays, etc. between the VFD output and the motor. They require low level programmed inputs to carry out their run functions, these and the motor specs. will vary between machines. So not plug and play. It is true that some VFD's have may have 2 sets of motor parameters, but the cost of the switch gear/wiring between machines and the proper inter-locks and different controls make it impractical vs. the cost of individual VFD's for smaller motor applications. Other option would be a Phase Perfect which does generate pretty close to sinusoidal output of an additional phase for 3 phase and can power multiple machines at once or individual within its rated load rating. There have been a number of threads as to use them in the UK, since it only generates a single phase. Best to speak to them if it is something you want to pursue and it fits your budget.
Using a US manufactured digital phase conveter in the UK | Physics Forums
Phase Perfect
 
There are many folks who actually do that.

It clearly helps if the motors are similar. And if you run in plain V/Hz mode, so no special calculations and measuring of the motor by the VFD is needed.

Unplug one machine, and plug in the next. that's basically what they do.

It may not be perfect, or ideal, but it does work....
 
^^^ What JST says for the cheapest solution. Don't bother buying the VFD until you get over here, they are readily available. If shipping cost isn't a problem (I guess not, compared with the cost of shipping the machine tools and houshold goods) then the starting surge of the rotary converter can be vastly reduced by using a pony motor to bring it up to speed before powering it on.

Rotary converters are readily available over here as well.

I currently run my workshop from a 415 TECO VFD that was modified by the supplier so that the internal supply acts as a voltage doubler and allows it to produce 415V three phase from our 240V single phase. The VFD is wired to all of the machines and once it's turned on, I run the machines exactly as if they were fed from the utility's 3 phase supply.

That brings a different question:- Are your machines all 220V three phase? If they are, then an appropriate 240V VFD will be able to produce 220V 60Hz three phase from the 240V 50Hz single phase supply with no modification at all.

Mark
In Rugby, Warwickshire.
 
One of the general rules with VFD's, is no switches or controls between the VFD and motor, is my understanding.
I've used a VFD for more than one machine, but only one at a time, sized for biggest.
It is easy to put some sort of plug and receptacle (socket) in for the 3 phase motor cable, to allow change from machine to machine.
But more difficult for the control wiring. In the past I've wired a simple low voltage receptacle to the VFD control circuit, then ran a lightweight control wire from each machine to this socket, thereby being able to control the VFD from the machine.
Programming has never been an issue for me. The only functions I setup within the VFD are:
- allow external control to switch VFD on/off.
- starting ramp (how quickly motor starts up, maybe important for a flywheel)
- braking resistor operation, to slow machine quickly - lathe spindle for example.
Once set, these parameters don't really need to change machine to machine; just a compromise.
VFD's are great !!!

However, I've just got a heavy Bridgeport style mile (Supermax YC-2VAS) with three 3ph motors on it: 5 hp spindle, 2 hp X/Y feed, 1 hp knee feed.
I'm thinking I need 3 inverters. If someone can convince me I only need one, I'm very interested to learn !

Kinda similar question to OP, so hopefully not a thread hike.
Thanks,
Bob
 
Hey JST. I was looking into the same kinda thing. I understand a bit out vfds and rotary phase converters and such, and the option for use on multiple pieces of equipment was presented to me from a very smart electrician at work. He was mentioning that you run VFD with 230 VAC single phase input and 230 VAC 3 phase out put and then place a 3phase transformer that goes 230 VAC 3ph to 575 VAC 3 phase between the VFD and the motor. VFD still has to be rated for higher HP rating, so perhaps 7.5-10hp rating for a 5hp motor You have a time delay on the VFD for when you turn on the machinery equipment and you are basically just using the VFD as a phase converter set to 60hz, as all the other motors will be 60hz. I might be wrong but he said the smaller VFD's like below 10hp I believe are good for doing this. Then you can have multiple machines hooked up at once (not necessarily running all at the same time however, since the power draw might be too much). This also allows you to use your factory controls on the lathe or whatever that piece of equipment is.

Does this work?
 
............................

Designers expect rude environments. Its a major part of what they paid us for!

At least they SHOULD. Sometimes the bean counters don't agree.

I've designed several VFDs that were INTENDED to have the load simply switched on and off instead of using the VFD slow start.

You know what was different? Nothing, except that the IGBTs had to be able to stand the load motor being switched on at full voltage, which causes a large current surge.

NO special protection for turning the motor off. The IGBTs with built-in diodes already handle the current being shut off tens of thousands of times per second....

That said, some makers actually say not to do it. Since I don't know their reasons, I suggest going with what they say, even though engineering-wise, there are very limited reasons for that restriction.

Some specifically allow it. If you really don't want to modify the machine, you can use theirs. But if you DO want to simply turn the machine on and off while on the VFD, you will need to get a VFD rated to handle the start current surge.

Many VFDs have 150% short term current allowed, some have 200% allowed for maybe 2 seconds, which should start almost any motor that is going to start. You can use that overload capability in sizing the VFD. Just don't cut it too close on ratings, and be aware that ratings may change with temperature (they go DOWN). I like at least 25% "cushion", or margin, over the probable motor current, if possible.
 
My experience, exiting "hollow state" for dawn of the transistor age, onward, it was always the CONTROL circuitry that was uber-fragile.

Confuse the controls the wrong way? They can destroy the pass-elements FOR you!

:(

Early digital logic tribes were horribly susceptible to confusion from any fast-rise transient, and power-handling goods adjacent produced *plenty*, plus carried-in more-yet from line and load as "antenna farms'.

...................

That has not been a problem with newer devices. The early ones barely worked to begin with, using old-style straight bipolar transistors, which had lots of problems when used at the high voltages needed in VFDs.

The issue is, for any decently and competently designed VFD, just the start surge if you intend to run a shop of standard machines and turn on via their switches.

For what the OP is suggesting, there is no issue. He's just going to use different motors with the one VFD. And use it As a VFD, not just a 3 phase converter.

That works.

The one downside is that the VFD has to have the current limits set for the biggest motor, which means the smaller ones are not as well protected. That problem may exist when using "wall power as well.

OK, one other issue is that the machine controls should not be used, because the VFD cannot start the machines at full voltage. So they may need modification.

If you start via the VFD, and can avoid having your muscle memory making you hit the machine switches, it's fine. Otherwise you may find it less trouble to bypass the start stop on the machine.

A rotary converter is a no-modification option, assuming all machines are good with 50 Hz.
 
That brings a different question:- Are your machines all 220V three phase? If they are, then an appropriate 240V VFD will be able to produce 220V 60Hz three phase from the 240V 50Hz single phase supply with no modification at all.

Mark
In Rugby, Warwickshire.

Yes they are, except for the radial arm saw. I specifically went in search of 50/60 hz tooling, because my wife and I knew this day was coming for some time. The only tool I had to let go was a small belt sander and one of my angle grinders.

Thank you for all the advice. I will take everyone's advice and set up an RPC and maybe one VFD for the saw.

I did always wonder about that above, why can't you just set up a VFD to run a big motor and use that as an idler, like an RPC, to allow load switching on and off. I can't imagine it's any more different than using a horizontal mill and letting it get to full load after starting it on a VFD.

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Thank you for all the advice. I will take everyone's advice and set up an RPC and maybe one VFD for the saw.
Blighty actually HAS tools and machinery, Mate. Also realistic freight off the Continent of Europe.

I would not drag ANY of my machines with me. I'd want different ones, anyway.

English. Scottish. Belgian. Nederlands, French, Italian. Czech. Austrian. Swiss. Swedish. Bulgarian. Polish...

German, even? Meahh...

:)

I did always wonder about that above, why can't you just set up a VFD to run a big motor and use that as an idler, like an RPC, to allow load switching on and off.

It can work. But it isn't electrically nor economically efficient for MOST cases. So it isn't that one "cannot". And knowing what I can buy IN Blighty... or near-enough?

I would not.

The reverse, OTOH? I HAVE .. twice - had "Angel Case" crate and ship a substantial collection of high-grade tools and metrology bought IN the UK and Switzerland BACK .. to the USA. I routinely buy from UK suppliers online, yet today.

One needs to scout for value, same as anywhere, and UK and EU costs are tax-ridden high. At least from HERE I am spared the VAT vampire-bite. You'll have to stand THAT bit of economic shock, full-hit once landed.

Rule of thumb is it takes twice the income in GBP to support a comparable lifestyle, mobility, space, and choice of clothing and diet as it takes, US side of the pond, in USD.

Double. In GBP. Not converted.

But you cannot GET it.

So your overall standard of living drops. A lot.

And in one-half to one-third the living space.

Most Septics - or Canadians, even Oz - haven't a klew how relatively well-off we have been for so long on the "materialistic stuff". SPACE ..and affordable autos.. on the list.

Not unless they have lived and worked in UK or EU for at least half a year, not just toured and visited.
 
I did a cost analysis of bringing versus buying "new" and it's actually cheaper to ship mine than buy similar ones over there. I did let some go that the market value is better than over here.

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I'm rather enjoying talking to you sir. Yes, unfortunately I have been stuck in CT for a decade. I'm far from a blue guy though. I grew up in WV and must admit I miss it very much. My wife was born and raised in Pontefract, UK, which is the reason I am moving back there. I guess you could say it is time for a change. We own a house there already and I've been over more than a few times for both visiting family and work related reasons. Now don't get me wrong, there are some tools I would straight up admit are better designed than our American versions. For instance, I sold my table saw here in the US last year because a Wadkin PK is, in my opinion, one of the best ever designed. As far as a Van Norman vs a Dekel or Abene, I'll admit I enjoy running a Van Norman much more, hence, I'm bringing that. Now, welders...I digress.

I have to laugh, at the cost of living, again though, I once made the mistake of going to B&Q to order 2x3s and found out it was not cheap. While unloading, a guy from up the street, came up grabbed them, through them back in the van and said, "Hey Yank, take those back and get on over to a Lumber Merchants." Needless to say, he was right.

P.S. My wife wants me to thank you for buying UK when you can.

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There are commercial VFDs that provide multiple motor profiles to be stored in memory. These can be activated by hardware switching.

Toshiba TOS-VERT is one example.
 
When all this is said and done, you can still consider retaining your rotary converter. If these are started *not* via start capacitors, the inrush is very small.
 








 
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