Phase converter vs VFD

[Bushmiller]

Sorry to bore you blokes with yet another discussion on the perennial question of how to get three phase power from single phase.

I have recently become aware of phase changers which appear to be a viable alternative to hooking up three phase instead of going down the VFD (VSD) track. Have any of you had experience with these?

As far as I can see there are advantages and disadvantages for both:

VFD Advantages:

Cheap (particularly with the imported versions)
Provides a soft start with reduced current draw.
Offers variable speed capability which is particularly attractive for machines such as lathes.

VFD Disadvantages:

The cheaper versions may not be as robust as they could be negating some of the cost advantage.
Some difficulties in wiring depending on the configuration of the 3ph motor.
Each machine has to have it's own unit
Limited in size to you largest GPO (which for most will be 10 amp or 15amp) which will normally be around 3HP.

Phase Changer Advantages

Unit is (I think) relatively robust.
Capacity to plug many different machines into the unit just with the plug. Of course this is only up to the capacity of the unit, but it is easy to swap machines over.
Hard wired versions can be installed up to the limit of the single phase wiring (7.5KW or even 10KW). Up to 4KW versions can be plugged in to a GPO (assuming you have the correct sized GPO, which would be 20amp for a 4KW unit)

Phase Changer Disadvantages

High initial cost (but cheaper than installing 3ph)
Will require extra wiring for larger units.
Not an option if the property is rented.

I know plenty of people using VFDs very successfully, but have not encountered any use or reference to Phase Converters. We have one at work, which is a very small unit powering our sliding security gate.

I did ask a question about start up currents and apparently the units are configured to cope with this. In my case I could plug a phase changer directly into one of my 20amp outlets, but needless to say I am greedy and want more :- .

Faced with the potential to go big I really want to captilise on the potential say up to 6KW. The maximum size is, as you probably realise, limited by the size of your incoming line to your property from the grid.

It seems to me that the phase changer option becomes more attractive as the number of 3ph machines increases and providing you don't mind having to plug them in each time you use them.

Any experience of these machines or thoughts or points I have missed would be appreciated.

Regards
Paul

[BobL]

Each machine has to have it's own unit


This is not necessarily the case - it would be possible to wire up a shed with one BIG VSD provided some additional wiring was used for safety switches and some interlocks required so that machines could not be disconnected while running. One problem with doing this would be to take full advantage of the programability of a VSD it would have to be reprogrammed every time it was switched to a different machine that had different parameters.

Even if I had a phase converter I would still install a VSD on just about every 3 phase machine for the control features which makes the converter a bit redundant. So far I have 3 VSD, MW and WW lathes and I just put one on my DP and I am loving it more and more. The belt sander I am making is getting one as will my WW bandsaw. I am also looking at making a variable speed gemstone grinder for SWMBO using a small 3-phase motor and a VSD.

The real icing with VSDs is the programability which I don't think we have really begun to use anywhere near to their abilities.

[Bushmiller]

This is not necessarily the case - it would be possible to wire up a shed with one BIG VSD provided some additional wiring was used for safety switches and some interlocks required so that machines could not be disconnected while running. One problem with doing this would be to take full advantage of the programability of a VSD it would have to be reprogrammed every time it was switched to a different machine that had different parameters.



Bob

I agree that it is possible. Not really in practical terms however, both from the different power and end use characteristics as much as the exponential cost once you get into the industrial (larger) range of VFDs.

In practical terms few of us are keen on swapping machines around any more than neccessary.

At this early stage of investigation there are two big issues.

Cost is the first. I can buy probably five VFDs averaging around $200 for about a grand. A single Phase Converter is around three times the cost for a 4KW system and four times the cost for a 6KW system.

The second issue I have alluded to above in that the size is more restrictive with the VFDs.

Having said that, if I hard wired a VFD, I might be able to run larger motors, but that also restricts me to having the machines in a relatively fixed position.

I have a number of three phase machines I cannot use in my current location (Jointer, table saw, spindle moulder, stroke sander, radial arm saw, blade sharpener, bench grinder) so I have the incentive to go down this track.

Regards
Paul

[RayG]

Hi Paul,

You seem to have a pretty good handle on the pro's and con's of VFD vs Phase Converter.

There are a couple of additional advantages to a phase converter.

First, and may be significant for some types of machines. You can switch the output of the Phase Converter, so for oddball dual speed and or reversing setup's that can be a deal breaker for VFD's

Second, Sometimes it's not easy to convert the control gear from standard to VFD control.

Third, Motors that can't be easily rewired from 415 3ph to 240V 3 phase, Phase Converter will give you 415.


That said, I have nearly all my machines running off 240V 3ph vfd's and don't own a phase converter..

Horses for courses I guess.


Regards
Ray

[RustyArc]

As mentioned, the ability to have 415v three phase from a 240v single phase supply is one of the major benefits that comes to mind from a phase converter, otherwise you need to make sure each 3ph machine you want to run off a 240v VFD can be rewired from star to delta.

Portability-wise, you can hard wire and mount the VFD to the machine and have it supplied by a plug, it's just that you start to get into the more exotic plugs as you increase current, and obviously you'll need matching sockets.

[Bushmiller]

Thanks Ray

I am aware that not all 3PH motors are easily adaptable to VFDs and that it what particularly phases me (sorry :-).

For example, my jointer has a star/delta starter. I imagine that I would dispense with the star aspect and just use delta with a a soft start programmed into the VFD if I travelled that path. However, I am beginning to get out of my depth with the wiring differences. That is not a huge issue as I work with electrical colleagues who offer advice even if I don't want it :rolleyes: .

Regards
Paul

[Bushmiller]

Thanks RA for your comments too.

As soon as a plug is involved at the 240V supply end I am limited to 20 amps and about 4KW (5HP). That is still not to be sniffed at, but I have caught a whiff of 6KW available which I had never even considered before. I think I have found a few testosterone enhanced blood cells I thought had long since flown the coop!

I had at one time considered connecting 3PH to the property, but quickly realised that even if I didn't drown in the paperwork (the distributor can't just give a ball park figure over the phone) the cost was going to be prohibitive.

As it is, the Phase Converter option will still require me give up a few necessities of life (alcohol and chocolate, not necessarily in that order) and I can see SWMBO's addiction to shoes and clothing taking a king hit. In the food stakes I see sausages taking more prominence.

Regards
Paul

[chambezio]

Paul,
I have been running a 3 Ph Converter now for 18 months. I have it to drive a 12'' Jointer with 3Hp motor, a12" Thicknesser with3 Hp motor and an SCM Panel Saw which has a 5.5 Hp on the main 12" blade and a 1Hp motor on the scriber. The Converter is rated at 5Hp, but it seems pretty happy to run the main blade and scriber OK (6.5 Hp total)
I hunted around the net to find out what I could and ended up with "mind overload". Eurotech in NZ seem to be the most "out there" with components or complete units.
I had to source a 5Hp idler motor (which generates the 3 legs of power) a 5KVA transformer (Off an old welder) to give you 415 Volts, a "black box" from Eurotech which manages the whole unit. Other bits you will need are a 3Ph contactor to turn the 3 legs on a circuit breaker on the 240 Volt side to protect the whole set up.
I have it plugged into a power point on the face of the distribution board and serviced with a 25Amp circuit breaker. The heavy lead going to the Converter is only 3 metres long.
The idler motor was easy and cheap to get but the transformer is a bit harder. A Forumite put it together for me and its been working fine.
When it was finished we measured to voltages across the 3 legs and they were within 15 volts (from memory)
All up I suppose it cost me $750 (I think)
Due to its ruggedness in design I think it could be more reliable than the VSD being printed circuits etc

[Bushmiller]

Thanks Rod

That's very interesting. I have seen that it's possible to put the components together and from your pricing there is clearly a considerable saving. In fact the saving would be a third of the cost of a comparable unit bought whole. This is a link to an Australian manufacturer, who you may notice also advertises on our forums. In fact as I type, I see their advertisement exactly to the right :) .

I now feel obliged to announce I have no business interest in their company, nor do I know them or anybody who works for them. I have spoken to them by telephone and they were most helpful.

Phase Change Converters - converting single phase power into 3 phase (http://www.phasechanger.com/)

Of course, as we do on the forums, I am seeking impartial advice particularly as it is unexplored territory for me. There is a possibility I can catch up with you when I come through Tamworth with a load of timber on 25th of this month. If that eventuates I'd love the opportunity to pick your brains. Whether you will be so comfortable with that arrangement is another matter :D .

Regards
Paul

[chambezio]

Yeh Paul,
I thought when I read your post that it may be beneficial to you to see my set up. From what you have already said I think you are in a worse predicament than I was in ie- you have a string of 3 Ph machines and no juice. I had the 2 planers for more than a year before I got my 3 Ph sorted out. The 12" thicknesser is an old Jeffwood, made in Qld, its got to be 1950s era. you can put a bit of old dry hardwood in and out it comes nicely planes with no complaints. the 240Volt one that it replaced would accept the timber but you had to go to the out feed side and pull. Not very satisfactory at all
I will give you a PM of my details and who knows you may have a little time up your sleeve.

[RustyArc]

The plusses of phase converters aside, it's worth considering the benefits of a VFD, which have, admittedly, been mentioned above - the ability to adjust the ramp-up and ramp-down time gives you a soft-start that you can tweak to suit the momentum of the machine, and there isn't the dimming of lights from the 6x startup current of a DOL motor.

Also you do away with contactors, so no clunk when you start (or series of clunks if you have a delta-star start), and you can program protection for over-current and under-voltage events, you can over-clock the motor for more RPM, and you can use the inputs and outputs to do useful things like automate the operation of a vacuum unit when the machine is up to speed.

As for plug-in connections, if the circuits have the capacity, I believe you can get single-phase plugs up to 32A.

[Stustoys]

Hi Paul,
I dont understand your comment "Limited in size to you largest GPO (which for most will be 10 amp or 15amp) which will normally be around 3HP."
You can buy 240V single phase to 415V 3 phase up to at least 25hp (of course they arent what you would call cheap)
Its your 240V supply that will be your limit and I'd think a vsd would do move with limited amps than a phase changer.

This one 25 HP 220V to 415V 3 PHASE DIGITAL INVERTER CONVERTER LATHE MILLING MACHINE SAW | eBay (http://www.ebay.co.uk/itm/151004497128) can also what he calls "plug and play" which means you can plug your 415V machine into it and use all the controls as if it was real 3 phase(though I guess you lose much if not all of the speed control)

Stuart