Phase Converter VS VFD what are the differences [Archive]

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joez

19th Apr 2018, 10:28 AM

caskwarrior

19th Apr 2018, 11:35 AM

Phase converters are noisy and fairly inefficient, Americans seem to like them but really VFDs are way cheaper and give you variable speed. As well as things like resistive breaking.

Think of rotary converters as a 1 phase motor turning a three phase generator. VFDs are a big box of capacitors and switching to give you an (very good) approximation of three phase power.

For the price of that one phase converter you could buy 5 good vfds

BobL

19th Apr 2018, 12:56 PM

The link to the ad you provided states;
"This product provides more power to the tool motor, and also brings it up to the required speed, much faster."

This is stretching things a bit. The new generation VFDs are very impressive in what they can do in this regard and as caskwarrior says, rotary phase converters are not very efficient to begin. Besides, a motor draws whatever power it needs from the supply (either a rotary phase converter or a VFD) depending on the load. Provided the power supply can exceed the motor power demand it will generate the power. The bit about bringing it up to speed faster is debatable - if there is a difference it will be in the millisecond range.

As for "simplicity and convenience", that depends. One thing that really annoys me and is safety factor is constant reconnecting machinery to mains power and power cords trailing across floors.

At the men's shed, the metal work area has 2, 3P sockets and about a dozen 10A GPOs, and when I used to attend I was sick and tired of constantly plugging and unplugging 3Phase Welders, drill press, drill mill, lathes, bandsaws, grinders and a linisher, with multiple extension cords running across the floor. Apart from the welders, all of the other machines were less than 2HP , I worked out for the cost of purchasing 3P sockets, wiring and breakers for each machine (the shed has its our own in-house sparky) was more that the cost of a basic VFD for each machine. Then all these low powered machines could have sat connected to 10A SP GPOs and be used without cables across the floor and constantly needed to be reconnected.

I know this not quite comparing apples with apples because if we were to factor in the cost of any motor modification etc the VFDs it would have cost more but its a matter of dealing with what one has available. Of course I did not suggest this as muggins here and our resident sparky would be the ones doing it and we have many more urgent things to attend to. Besides, reconnecting machines gives the members something else to while away their time :) Some of these machines were recently replaced by SP machines at considerable expense.

The issue with VFDs is the learning curve and sorting out how the motor and VFD can play nicely, but once you overcome these there are so many advantages to using VFDs that you'll wonder why they are not used more often.

Of course if you don't have the $$, or time or inclination to get up to speed with VFDs then a rotary phase converter may better suit your immediate needs

paul33

19th Apr 2018, 03:23 PM

It depends on the type of mill, your usage and your future plans.
If the mill has multiple motors, eg. for a coolant pump and table feeds, then the rotary
phase converter will do the job out of the box.

VFD's generally are good for direct connection to one motor only.

If you are planning to purchase other old 3 phase machines, a VFD will be required
to be installed/configured for each machine. With a single rotary phase converter it will be easy.
However, rotary phase converters are generally noisy, inefficent, heavy and expensive.

If you are planning to run the mill for a lot of hours a day, it would be worth the time and effort
to install and configure a VFD for it.

OxxAndBert

19th Apr 2018, 05:51 PM

I built my own rotary phase converter and can attest to them being heavy (mine has a 5kW idler and a 5KVA step-up transformer) and probably weighs in excess of 90kg. Cost around $1000 and I burnt a heap of time building it and getting it running OK.
Not sure about the noisy part though as mine just gives a very slight hum when running - I definitely wouldn't consider it noisy.
My lathe has a dual speed motor as well as a foot brake with motor cutout, and also a coolant pump - so not just a simple case of wiring up a VFD for a single motor. That was a major part of my decision to build the converter rather than go the VFD route.
My mill has 2 motors, one for the spindle and one for the table feed. Again - not so easy to run from a VFD - but by that stage I already had the converter so it was just plug and play.

The converter does provide a simple/dumb plug and play 3-phase power source so its easy to plug in other 3 phase machines - I've since acquired a power hacksaw and surface grinder.
Yes, you will be able to just plug in an old mill if you buy one - providing the converter is of sufficient size to run it. Depending on how its rated, a 3KW rotary phase converter will likely not be big enough to run a 3KW motor.

Another downside is that they are very dumb, and you need to have a good circuit to run them off. I was sometimes tripping the breaker on a 15A circuit due to startup current demand on the lathe (geared heads and big chucks have a lot of inertia to overcome), so I've now put in 32A circuit.
I don't have any VFD experience but understand they can be set up to be a lot softer starting and generally more efficient therefore keep the current requirements down. Something to keep in mind if your workshop cabling is a bit on the marginal side.

I can see in the future I'll likely end up setting the hacksaw and surface grinder up in more permanent locations with VFD's just plugged into normal 240v outlets. They're only small motors with simple on/off so should be easy to set up. A VFD for the mill spindle would be nice for speed control.

Just had a look at the link you posted to the digital converter. Looks to me like it could be just a VFD in an expensive box. You'd want to check out whether its going to be happy running a machine with multiple motors and original switching etc if you were considering that option.

Steve

BobL

19th Apr 2018, 06:33 PM

I built my own rotary phase converter and can attest to them being heavy (mine has a 5kW idler and a 5KVA step-up transformer) and probably weighs in excess of 90kg. Cost around $1000 and I burnt a heap of time building it and getting it running OK.
It sounds like you knew what you are doing, but given the cost and time involved (unless it was something like a welder) these days I'd recommend putting time and energy into learning about VFDs.

I don't have any VFD experience but understand they can be set up to be a lot softer starting and generally more efficient therefore keep the current requirements down. Something to keep in mind if your workshop cabling is a bit on the marginal side.
Yep, this is how I started and ran a 4HP, 3P compressor from a 240V 15A GPO on a 20A circuit and breaker. I used a 5HP VFD current limited to 17A and set the motor acceleration time for 10 seconds so it didn't exceed the breaker currents during start up. Normal compressor recharge currents were ~15 A but using a "zero VFD acceleration time" start up currents very briefly exceeded 100A (that's as high as my V/I meter goes on the compressor circuit) and would trip the 20A breaker - even a 25A breaker.

I can see in the future I'll likely end up setting the hacksaw and surface grinder up in more permanent locations with VFD's just plugged into normal 240v outlets. They're only small motors with simple on/off so should be easy to set up. Sounds like the way to go given the price of VFDs and how well they perform these days.

Just had a look at the link you posted to the digital converter. Looks to me like it could be just a VFD in an expensive box.
You are correct, it is a VFD.

However, I don't want to make VFD installation sound too rosy. In the Woodworkers forums Electronics subform there is a detailed thread showing most of my adventures with VFDs. VFD install summaries (http://www.woodworkforums.com/f271/vfd-install-summaries-213878)
In this thread you can read lots of grimy details about VFDs, the pitfalls to watch out for etc. Also a number of other members have posted their VFD experiences as well.

I'm in the middle of converting my 1.5HP DP from a non-vector drive to a sensorless vector drive VFD. These drives which provide more torque at low RPM used to be expensive but are now similar in price to the non-vector drive models providing yet another reason to look more closely at VFDs. At first I thought it was going to be a simple swap but I have decided to go any with a small vented die cast Al enclosure - waaaay more work than I bargained for as I had to change the support brackets etc - it's rarely straight forward.

Vernonv

20th Apr 2018, 03:07 PM

I built a rotary phase converter, but have also used a VFD where I wanted a machine to be stand alone single phase. Here is my take on phase converters:

1. They are quiet - just a the sound of a motor running. I have left mine running on occasion because I forgot (and couldn't hear that) it was on.
2. They are the best way to go for machines that have multiple motors in them.
3. They are the best way to go if you intend on having multiple 3 phase machines in your workshop.
4. They are the best way to go if you intend on having large 3 phase machines in your workshop.

Cost wise RPC's can be very cheap to build if you have a bit of electrical nous (or know someone who does) and do a heap of reading. My RPC cost less than $200 and contains a 5hp motor and a 20KVA transformer. The transformer I got was brand new and cost $100. Old multi voltage welders are a dime a dozen ... I picked one up for around $20.
The time and cost required to build an RPC for the situations I mentioned above, would be easily comparable with buying and installing/setting up multiple VFD's.

YMMV.

OxxAndBert

20th Apr 2018, 04:35 PM

My RPC cost less than $200 and contains a 5hp motor and a 20KVA transformer. The transformer I got was brand new and cost $100. Old multi voltage welders are a dime a dozen ... I picked one up for around $20.

$100 for a 20KVA transformer is damn cheap. IIRC I paid around $600 for my 5KVA one (240-415v single phase), and that seemed to be about the going price of anything new.
Did you just get lucky with an old stock one or is there a alternative style that can be used to do the same job?

I actually had a crack at using an old multi-voltage welding transformer as an auto-transformer before buying a real one. Unfortunately it turned out to be a multi-coil arrangement for the primary instead of a simple multi-tapped one and although I had no trouble wiring it to get the correct voltages it sagged very badly under the starting load on the lathe to the point where the voltage was low enough to cause the main contactor on the lathe to drop out.
It was likely just something simple but it exceeded my knowledge and patience at the time so I coughed up and just bought a proper transformer. A number of issues I'd been working through disappeared instantly :)

Steve

Vernonv

20th Apr 2018, 04:49 PM

Did you just get lucky with an old stock one or is there a alternative style that can be used to do the same job?Yeah it was surplus stock, that they just wanted to get rid of. I couldn't believe my luck.

I built an RPC for a fellow forumite and if I remember correctly the transformer was an old multi-voltage welder. I don't recall that we did anything special with the transformer and he has not reported any startup issues to me.

BobL

21st Apr 2018, 10:38 AM

The relative efficiencies of Rotary, and Digital Phase converters (RPCs, DPCs) and VFDs has already been mentioned in this and other other threads but it's interesting to put some numbers on it.

RPCs can be up to 30% less efficient than DPCs and VFDs and the electrical power costs involved may not make them seems so cheap even if you build them yourself.
This is because RPCs use an additional motor and often the RPC and its associated motor is left on even when the 3P motor on a machine is not and this consumes power. RPCs also have a poor power factor which contributes to these losses.
In addition the converter motor also has to be oversized to provide the start up currents.

A 4kW RPC running with 25% losses for a day consumes an additional 8kWhr or ~$2 more or less whether you're use the output of the RPC or not.
A 3kW VFD costs ~$200 so in ~100 days of operating the RPC you would have paid for the VFD and over couple of years of operation you could have fitted all your workshop machinery with VFDs

I realise this may not be that significant for the occasional/DIY user situation but if you are not then it's something to really think about

DPCs cost a few % more to run than VFDs.
Both of these devices generate generate harmonics which in the case of VFDs cause losses back at the nearest supply transformer so are not charged to you. OTOH DCPs filter out these harmonics internally and thus you are charged with these losses.

Vernonv

23rd Apr 2018, 08:39 AM

RPCs can be up to 30% less efficient than DPCs and VFDs and the electrical power costs involved may not make them seems so cheap even if you build them yourself.I think if you are concerned that your machine is costing you 31 cents an hour to run as opposed to 24 cents and hour, then you probably shouldn't buy machinery. It is my experience that the electrical running costs are the least of the costs involved in running a metalworking machine (machine purchase, tooling, maintenance, etc) and that is no more so than in a hobby situation.

BobL

23rd Apr 2018, 09:48 AM

I think if you are concerned that your machine is costing you 31 cents an hour to run as opposed to 24 cents and hour, then you probably shouldn't buy machinery. It is my experience that the electrical running costs are the least of the costs involved in running a metalworking machine (machine purchase, tooling, maintenance, etc) and that is no more so than in a hobby situation.

I guess it depends on your circumstances and where you'd rather put your money. As a retired bloke with limited funds I've found every cent saved does add up. I scrounged most of my machines for nothing or next to nothing and use second hand parts and scrap materials wherever I can - this is also typical of many hobby operators. This is what enables me to buy the odd bit of tooling, VFDs, and materials I can't scrounge. It's the same reason I spent $100 on LED fluoro tube replacements for the shed, use my seniors card at the supermarket and the (saves me about $2 every time I use it) collect my 4c/L fuel discount (a whole $2 a fortnight on a tank of diesel) and use a bunch of other discount cards. It all adds up.

Vernonv

23rd Apr 2018, 10:12 AM

It all adds up.I agree, but we are predominantly hobby users on here and I would suggest that with the relatively small amount of ACTUAL use these machines get, the ACTUAL difference in electrical running costs are insignificant on balance.

However, if you are an industrial user, or even a small (hobby sized) manufacturer, you would be using proper 3 phase and/or you would be factoring in the electricity costs into the price of your product/service.

Don't get me wrong, it's horses for courses and VFD's are perfect for some situations where RPC's aren't ... but I just don't see the "efficiency" argument being valid in the hobby situation.

Theberylbloke

25th Apr 2018, 09:55 AM

However, if you are an industrial user, or even a small (hobby sized) manufacturer, you would be using proper 3 phase.

The assumption here being that three phase is available to your premises or that you are prepared to pay to have it put on and pay to use it.

If the high voltage three phase ends before the distribution transformer that supplies your property, then you will want a very very good reason to get three phase mains supply due to the installation and operating costs involved. In my situation the three phases ends 8 spans from my transformer. That air gap alone would cost tens of thousands of dollars to bridge. Then a transformer upgrade, overhead mains upgrade, service upgrade, consumer mains and finally the switchboard upgrade. Then running costs. Hmmm....:no:

Better, in my opinion, to use a VFD and step up transformer to synthesize 3 phase and back it up with three phase solar possibly hybrid and small batteries.

Not everyone is in my situation and your mileage may vary.

I am not keen to use a rotary phase converter. Among the pros and cons not mentioned above is that the phases produced by a rotary converter are not 120 degrees apart, nor are the volts balanced across the three phasses when load changes. The result is more heat in the motors and less than rated power from them.

I have had it suggested to me that you could use a 240/415 volt step up transformer to supply 415 volt single phase that you run to each machine where a VFD then produces the three phase for that machine. Not sure I like this idea. What if you need 240 volt single phase at your machine as well? A step down transformer or wire in 240 volt single phase as well?. Multiple circuits, identical looking circuits with different voltages and multiple isolation points, what could possibly go wrong here?

The most important part of creating a 415v 3 phase "grid" from a 240v single phase supply is electrical safety. Specifically the fault loop impedance of the created "grid". If you use a VFD/step up transformer combination where you rely on the VFD overcurrent protection, then every circuit will have to withstand that fault current until the protection operates. One of the reasons why I've included battery backed solar above is to increase the levels of fault current on the created "grid".

I've had some concerns about the fault performance of such systems for awhile.

Recently, I got some photos of what happens when fault current flows in a conductor but circuit breakers/fuses don't operate. The insulation had melted/burnt on several circuits and the repairs to the house wiring took 2 guys a bit over a day to complete. One photo from the ceiling shows burnt wires having scorched the gyprock sheeting. A piece of cardboard that had been lying on top of the cable had caught alight and burnt back and only extinguished when the insulation on top of it had smothered the advancing flame. The fault current had flowed for possibly 10 to 12 hours and yes there had been at least one person asleep in the house during that time. If I can work out how to get the photos off my phone and get permission (there maybe legal issues), I'll post them to a new post.

Cheers

The Beryl Bloke

Vernonv

25th Apr 2018, 06:43 PM

I am not keen to use a rotary phase converter. Among the pros and cons not mentioned above is that the phases produced by a rotary converter are not 120 degrees apart, nor are the volts balanced across the three phasses when load changes. The result is more heat in the motors and less than rated power from them.True in theory, however in practice this doesn't seem to be an issue. I regularly run a panel saw and dust extractor (3 motors in total), a metal lathe (only a single motor) and a milling machine (4 motors in total) and have done so for years without issue.

The other advantage of an RPC over a VFD is that as well as being able to run multiple motors from the one "source", you can also run any 415V control electronics in the machine in question without needing a separate 415V supply.

Pulpo

27th Apr 2018, 08:24 AM

OxxAndBert

27th Apr 2018, 12:34 PM

Interesting topic.
I can think of various ways to convert single to 3 phase:
A few capacitors method: check you tube , not recommended but it works.
Rotary method: most common over the years; most points raised, I’m not a fan.
Have yet to see any video of phase balance from anyone, which always surprises me.
Transformer method: one of the best diy methods, check unique3phase on google.
It surprises me no manufacturer makes them.
VFD: for smaller machines 5kw and under this a great option.
Toying with the idea of a single phase transformer 240 to 400v 20kva a 30kw vfd to run the whole workshop; compressor, lathe a few other bits and pieces.
Finally the best a digital phase converter: see phase perfect. Out of my price range.
Maybe an electrical engineer could make one via arduino route?

My vote vfd

Good luck with your selection

Cheers pulpo

Apologies if its not the case, but from your post I'd say you don't actually have personal experience with any of these methods and what you've posted is just straight from the interweb.

I think if you understood how a RPC works and their limitations I don't think you'd be surprised why nobody posts phase balance videos. Likewise why the "transformer" method isn't something you can buy off the shelf.

Again, if that's not the case I apologise and would love to hear what you're running and how its performed for you.

Steve

Vernonv

27th Apr 2018, 06:25 PM

... a 30kw vfd to run the whole workshop; compressor, lathe a few other bits and pieces.
I've never tried it so I don't know the answer to this, but is it actually possible to run "whole machines" (i.e. motor(s) AND control electricals) from a single VFD?

I've always been under the impression that normally the machine's control systems control the VFD (tell it to run/stop and maybe set direction) and the VFD simply drives a motor based on that control.

Have I been misled?

jhovel

27th Apr 2018, 08:48 PM

I've never tried it so I don't know the answer to this, but is it actually possible to run "whole machines" (i.e. motor(s) AND control electricals) from a single VFD?

I've always been under the impression that normally the machine's control systems control the VFD (tell it to run/stop and maybe set direction) and the VFD simply drives a motor based on that control.

Have I been misled?Two versions nobody has mentioned yet: there are VFDs that connect to single phase 240V and put out 3 phase 415V. See Arc Euro in Britain. They cost around double the price of the cheapest Chinese VFDs. Still lot cheaper than an RPC.
Secondly, there are VFDs which are certified for motor-side switching. Again, about twice as expensive as cheap Chinese ones. Those will easily cope with auxiliary motors being switched on and off at will, though if their frequency is varied to change the speed of the main motor, then the speed of the auxiliary motors will change too. An RPC can't of course change frequency at all.
In the end, it's the buyer's choice. I would - and have - multiple VFDs on the same machine for a lot less money and much greater flexibility than an RPC.

Cheers, Joe

LexD

27th Apr 2018, 11:11 PM

I use one of these to run the 5hp motor in my Colchester lathe - Light Horse Series | Phase Change Converters (http://www.phasechanger.com.au/products/3-phase-converters/light-horse-series.html)
Although it is the 5.5HP converter it did struggle to get the spindle up to speed in the 2 highest speed settings unless I slipped the clutch for a couple of seconds, after that it ran perfectly and there is no problem at other speeds,this characteristic is mentioned in the phase changer literature.
I have now overcome this problem completely by fitting a 5HP 3 phase input-output VFD between the phase changer and the lathe motor with the added advantage of variable speed.

jhovel

28th Apr 2018, 09:49 PM

That would seem to be the most expensive way to achieve VFD control...

Cheers, Joe

BobL

28th Apr 2018, 10:17 PM

That would seem to be the most expensive way to achieve VFD control...Cheers, Joe

Maybe it was a 415V ∆ motor?

kwijibo99

29th Apr 2018, 12:46 AM

VFD's are great but they are not a universal solution to running 3~ motors from a 1~ supply.
My Thiel mill has a Demag brake motor and based on a discussion I had with one of the automation & drives blokes when I worked at Siemens there was some doubt that the 3~ 240VAC output from a VFD could operate the brake clutch correctly, even with the spring backed off so I went with a Phase Changer 4 and have never had any problems.
I've got a spare 3~ 415VAC VFD and have been thinking about setting it up with the mill, based on What Lex has said I might move this up the project list a bit.
Cheers,
Greg,

Pulpo

4th May 2018, 06:27 PM

Apologies if its not the case, but from your post I'd say you don't actually have personal experience with any of these methods and what you've posted is just straight from the interweb.

I think if you understood how a RPC works and their limitations I don't think you'd be surprised why nobody posts phase balance videos. Likewise why the "transformer" method isn't something you can buy off the shelf.

Again, if that's not the case I apologise and would love to hear what you're running and how its performed for you.

Steve

Its interesting how others interpret ones post.

I thought my post actually contributed to the initial enquiry.

Yes a tremendous amount of my knowledge over the last 14 years on this topic has been from the web.

I'm not an electrical engineer.

I first saw a phase converter (rotary) around 20 years ago, home made and always wondered is that "right".

Yes the motor ran no problems but balancing the phases both in voltage and current from single phase is the key.

I bought a CD about 13 years ago from www.unqiue3phase.com Doug Arndt he sold a few into Oz.

I also bought his latest book on three phase converters last year; well worth a read.

Sent a few emails to him, very knowledgeable.

I built one of his transformer phase converters; after a few house and work moves I lost it.

It worked perfectly once running on a dust collector system.

As only one previous post mentioned about the phase balancing and the loss of power.

This matters for motor windings and efficiency.

For a second hand piece of machinery maybe not that critical but I have seen a water pump three phase destroyed from a phase converter.

Also with equipment electronics this could be an issue.

Once I discovered VFD I could not understand why any one would use rotary method.

I love VFD for smaller machines.

They can be a pain to get set up particularly if you buy with poor or no documentations.

However VFD have limitations.

VFD have harmonic distortion (Total harmonic distortion THD) which can be an issue and one should be aware of.

As best I know all VFD will convert single phase to three phase.

Finally a few years ago I discover Phase Perfect (http://www.phaseperfect.com).

I thought it was game over for all other technologies; it is a game changer.

The price would suggest others still will have a big role to play.

So finally I realised that all methods have a place.

And Steve finally I am surprised why no manufacturer of rotary phase converters show on video how the phases are balanced.

Because this is the key to a phase converter, making a motor run from single phase is really only a small part.

They all have great marketing bs on their website telling the world how great the phase balance is but show nothing.

A rotary phase converter has change alot, with way more electronics, PCBs etc to years ago.

I own three 3 phase machines and have nothing running.

Low on my lists of priorities.

Thinking of also buying a 3 phase CNC machine, plasma cutter from China later this year (travel for work).

But am nervous due to electronics particularly THD if using vfd method.

Cheers

Pulpo

Pete O

8th May 2018, 11:21 AM

I'll chime in and share my experience in a home workshop just to illustrate my answer to what the OP was asking.

My first machine was a large (ish) 3-phase lathe. When considering the purchase, a friend gave me a VFD and told me I'd be able to run the lathe off it. I converted all the lathe switching to low-voltage signal for the VFD, this was great- I could vary the spindle speed from the VFD as well as setting the control parameters for soft-start, power braking on the emergency stop, etc. However, I had to set up a different input for the coolant pump, I use a 1ph 240v input and a bank of capacitors, there is a momentary switch that has to be held whilst switching on with another rotary switch. This works ok for a 1/8hp pump motor. Also, I was running a 3hp 3-phase machine off 3-phase 240volt- the VFD did not incorporate a transformer. I could do most of what I wanted to with the lathe but it would not spin the heavy chuck up to speed in top gear and would slow down with a heavy cut.

A couple of years later I bought a milling machine with a 4hp 3-phase motor. I was faced with going through the same process again of acquiring a suitable VFD, re-wiring the machine, having reduced torque capability etc. This did not appeal.

I built a RPC using a circuit diagram designed by a friend who was at that time building them for a living. The step-up transformer was the most expensive component, $450 iirc. 5kw idler motor from eBay for $80 and the friend got me all the switchgear and capacitors plus a cabinet for another $50. I suspect a realistic build cost without 'mates rates' would run close to $1k.

Plugged the mill into the rotary phase converter, solved a minor issue (see below) and started milling. Bought a 3-phase bandsaw, plugged it into the RPC and started cutting. Bought a shaper, plugged it into the RPC and started shaping. Bought a surface grinder, plugged it into the RPC and started grinding.

I found another VFD on eBay at a bargain price as it was 3ph input (those with 1ph in / 3ph out fetch high of bids as hobbyists without RPCs are clamouring after them) and my lathe now runs happily via this VFD downstream from the RPC. Now runs in top gear, also can take heavy cuts without stalling. The other VFD has been used to run a blower for my furnace, the power demand there is low so 240v 3ph works ok although I'll soon be running it off a treadmill motor and the VFD will be enlisted elsewhere.

The initial issue with the mill when I plugged into the VFD was that the contactor would not stay in- it was bouncing and arcing. Called my RPC expert mate and he told me I had the switching on the 'phantom' phase- rotate all the wires one position. I did this and have never looked back. The fact that this happened suggests to me that the 3-phase power produced by the RPC is not quite the same as the stuff the SEC used to make, but my machines do not appear to know the difference.

My RPC is push-button start & stop, with a single, switched 3-phase outlet on the side of the cabinet. I have an outlet on the wall behind my lathe, the plugs for the lathe, shaper and mill hang at that point and are plugged in as required. I ran another cable around the shed to where the bandsaw and surface grinder live. I can only plug one machine in at a time but that is all I need.

The idler motor is very noisy but it is mechanical (not electrical) noise, I guess it has square balls in the bearings and one day I will overhaul it. If it remains noisy I'll build a cabinet around it, or put it outside so the neighbours can listen to it. No reason why the idler motor has to be in the same place as the control panel.

I have a Bridgeport step-pulley J-head that I plan to graft onto my mill when time permits; I'll run this via the spare VFD with 3-phase input from the RPC, only because I happen to have one on hand and it may be a nice addition, speed variability without belt changes etc.

Turbine Builder

13th Jul 2018, 09:58 PM

Can anyone enlighten me, what are the differences between the 2 options?

Obviously, VFD's are cheaper and more flexible.

Am I right in thinking that phase converters are just plug and play? so basically if the load is ok you can just plug your machinery into it like a regular power socket?

If I purchased an old mill can I just take it home and plug it in?

I can pick up a 3kw phase converter locally for $2K, or a digital 2.2KW for $1020 seems like a simple, fast and flexible option for people with multiple machines...

https://www.ebay.com.au/itm/Maximum-3kW-Rotary-phase-converter-240V-Single-Phase-to-Three-Phase-415V/282812107295?epid=682265568&hash=item41d8ea4a1f:g:NyEAAOSwB-1Ywhnv

(https://www.ebay.com.au/itm/Maximum-3kW-Rotary-phase-converter-240V-Single-Phase-to-Three-Phase-415V/282812107295?epid=682265568&hash=item41d8ea4a1f:g:NyEAAOSwB-1Ywhnv)https://www.ebay.com.au/itm/2-2kW-3HP-Single-Phase-240-V-to-3-Phase-0-415V-Digital-Phase-converter-VSD-VFD/273003129090?hash=item3f90412902:g:uocAAOSwmOJaPIdP

G'day Mr Joez,
I decided to get three phase power installed to my shed all up cost was $4,000 you could get it done cheaper than this price if you can get the materials yourself and install the cable yourself but as the sparky told me he can not prescribed Certificate of Electrical Safety only for the work he does, so i had him do the full installation. Now as for RPC i was quoted $4,500 plus i need to have a 30 amp outlet and i only had 20 amp. I can not use VFDs as my lathe has three motors same with the mill. I had the three phase power in for over a year now best thing i ever did.

Cheers,
Mark.

BobL

13th Jul 2018, 10:35 PM

G'day Mr Joez,
I decided to get three phase power installed to my shed all up cost was $4,000 you could get it done cheaper than this price if you can get the materials yourself and install the cable yourself but as the sparky told me he can not prescribed Certificate of Electrical Safety only for the work he does, so i had him do the full installation. Now as for RPC i was quoted $4,500 plus i need to have a 30 amp outlet and i only had 20 amp. I had the three phase power in for over a year now best thing i ever did.

Not saying what you did was not the best option for you, but it's also worth knowing that $4000 buys a lot of VFDs.

I can not use VFDs as my lathe has three motors same with the mill.
Members are increasingly able to easily do exactly this using multiple VFDs
This then not only solves the 3Phase issue but also provides all the other benefits provided by VFDs.
Typically on a mill or lathe only one large and one or two smaller VFDs are required and all 3 can be had for <$500.
I'm talking about rubbish VFDs but fully featured industrial strength type VFDs.
The smaller ones also only take up as much room as an old style contactor switch which are n longer required in VFD implementations.

I just completed a twin small VFDs installation on my small mill and to add another VFD to teh system would not have been a lot more work.
The twin VFDs fit into the same cabinet space under the mill where the old contactors and a 32V transformer was located.
374223

More photos and a bit of a WIP from about this point on in this thread
http://metalworkforums.com/f189/t201814-finally-mill/page-2#post1935493

Like I said, it's not for everyone but it does mean it's not impossible.