digi phase converter for 10 machines…..

[clogsParticipant @clogs]

i cannot get 3phs from the elec supplier at my property….unless I pay £12,000's..

I have 10 x 3 phase machines to wire up in a new workshop….biggest is 4HP……

NOTE :- only using one at a time in this hobby shop…..

Looked at building a rotary unit but too complicated….and prob end up with as much money in it as a digi unit…..plus all the headaches…..?

I would buy a prebuilt rotary if one was available privately tho…..it just has to be plug n play…almost…..not bothered about new……

anyway,

I'd like plug n play so started looking at a Digi unit…….machines wired up via a perm ring main around the workshop….I do not want to plug in and out everytime I need a machine esp off an ext lead………

I have a 45amp x 240v supply at the mo but could be upgraded I guess…….

There's massive overhead wires at the supply pole…..

I'm thinking I need a unit that will handle 20Hp for safety/ overload/ future proofing……

looking on eBay, the cheapest 20 horse unit made in Korea at £600 and a UK made unit at £4,500…..

There's also 15HP unit from China at £1400…….

I know u get what you pay for but the Brit made unit is way overpriced I feel….even if gold plated……..

I'd still go for a 20HP unit even if it was to big, just to save a few bob/squids……

I live abroad and there's no warrenty cover prob on what ever I buy…..

Anyone done this and any recomends…….?

there's no way I'd put VFD's or single phase motors on these machines ….just too much money and too many of them…….

thanks…..hope this makes interesting reading….it cant just be me…..?

[clogsParticipant @clogs]

[noel shelleyParticipant @noelshelley55608]

I live in a village with only 2Ph ! Could you use a 3Ph generator ? If so then it covers all your requirements ! I built one using a peugeot diesel and a 20Kva alternator worked very well. The supply company may not upgrade when they know what you will use it for. As to costs You Only Get What You Pay for. Noel.

[Dave HalfordParticipant @davehalford22513]

Someone once said there was an issue with under-driving a VFD so much. The earth leakage may be huge

If they are all 250v 3ph then a 4hp unit is all you need.

[Robin DuftonParticipant @robindufton85682]

Why would you need a 20hp phase convertor if your largest machine is 4hp? The single phase supply you would need to run 20hp would likely raise more questions from the electricity board than what you would be doing with three phase. We recommend a 40A supply for when we supply machines running 5.5kw VFDs on single phase, and 20hp is pretty much three times that.

I know my house has a 100A supply, but I know new builds are lower, something like 63A rings a bell, so they would probably like to know why you would want a 100A supply. I'd go with the diesel generator suggestion if I needed that much beef and couldn't get three phase.

[EmgeeParticipant @emgee]

Hi Clogs

The rotary units here may be of interest to you, **LINK**

Emgee

[SillyOldDufferModerator @sillyoldduffer]

Clogs has a complicated problem!

Easiest and best answer is to cough up and pay to have a proper three-phase supply installed. Apart from the cost! Quotes vary enormously. I believe it's because the customer is billed for any and all extra infrastructure needed. Lucky folk are connected to a handy pole outside their front door for a few hundreds. Others trigger requirements for lots of new cabling, trenches dug across busy main roads, poles erected, and maybe a few transformers have to be upgraded too.

Big digital converters capable of running a mix of 'n' different machines exist, but not cheap. They're aimed at industrial users not hobbyists. Maybe prices have dropped and someone has experience?

One per machine VFDs are small, simple, cheap, and efficient but fitting 10 of them is a big job. Could be the right answer though.

The obvious answer is a rotary converter big enough to manage the largest machine. Not grossly expensive to buy, but take up a lot of space, and are noisy and inefficient. Drawing big power from a rotary for any length of time soon makes the alternatives look attractive. However rotary inefficiency may not be a problem for occasional hobby use, and they do what they do without fuss.

A big static converter might be OK too. I don't care for them because the phases aren't equally spaced, so some motors won't run, whilst others only perform after the switches are fiddled with. Whether all 10 motors in a workshop will run off a static converter without shenanigans is a risk. They're also inefficient and capacitors don't last forever! Cheap and cheerful: if a static does the job, you've won.

Dave

[Harry WilkesParticipant @harrywilkes58467]

You could contact Transwave for advice link

https://transwave.co.uk/

H

[Robin DuftonParticipant @robindufton85682]

Posted by SillyOldDuffer on 02/10/2023 16:42:26:

One per machine VFDs are small, simple, cheap, and efficient but fitting 10 of them is a big job. Could be the right answer though.

On the low end one 3kw VFD is £300, for a sort of trusted brand, and I buy Eaton ones for ~£500. Eaton 550w VFDs cost me £110 a piece. So across 10 machines of varying power requirements you're well over half way to the British made 20hp phase converter. Add in enclosures, switches, cable and time, you're well down.

In 2019 the cost for three phase for us was £1400. £900 of that was the permits and permissions required to dig up a 300mm square bit of pavement at the edge of the property. I know it is now triple that as more and more people want it for EV charging.

[Clive FosterParticipant @clivefoster55965]

I have 10 machines (I think, haven't counted recently) on a 10 hp Drives Direct boxes, which are modified Teco units, with the smoothing inductor add on on the back to clean up the output. Still going strong after over 10 years. Biggest motor is 3 hp and one is a two speed.

Normally one machine at a time but it comes just fine if the compressor, Hydrovane 502 with 3 hp motor, kicks in mid job.

Doing the maths at todays prices individual brand name VFD boxes would be cheaper if all the machines were modern enough to have dual voltage motors.

If I were to start over today I'd probably use individual brand name VFD boxes from Inverter Drive Supermarket and come out more or less even. Replace the two speed motor with a new 6 pole one and swop the Hydrovane 502 for the tripod mount 504 I just happen to have lying around (!) which will give me enough air running at the 850 or so rpm it could manage on 220 volts. Hydrovanes have 440 volt delta connect motors so no low voltage connections.

I'd be very chary of using an economy range VFD as a direct substitute for a proper mains three phase power switching motors on and off with the box running. Very very hard on the capacitors even when de-rated. There are alternative input rectifier configurations that ought to reduce the capacitor shock loading relative to a standard set-up. I presume the high cost of the Drives Direct boxes is due to installing such plus re-programming the box so it doesn't fall out on seeing only one phase on the input and/or high current demand on the output side when a motor starts.

Clive

[Robert Atkinson 2Participant @robertatkinson2]

Well you can't run a 20HP drive off 45A supply for starters.

The big issue with using a VFD is that they are designed to be permanently and directly connected to a MOTOR. They are not designed to drive control gear lights etc. The control gear almost certainly needs neutral connection which a VFD does not have. A single good quality 5kW VFD could run all your motors individually but you would have to interface the controls of each machine to the VFD. IF all the machines have just a single Start / Stop E-Stop control (and maybe reverse) than perhaps you could wire a single pendant to the VFD and then move it to the machine in use when you plug that machine's MOTOR into the VFD output.

To make it more fool-proof you could have a contactor at each machine that when energised connects that machine's MOTOR to the VFD. On each machine you have a socket for the control pendant to plug into. The paendant is interlocked with the contactors so only the machine that has the pendant plugged in is connected to the VFD.
A more complex variation would be to rewire the controls on each machine to a a set of relays that only connected them to the VFD when that machine was selected. That is a lot of work though.

There are some possible issues with VFD output cable lengths, EMC etc but it is workable. An output reactor may be required.

I'm surprised that you have ten 3 phase machines without a 3 phase supply. If only I had the room…..

Robert.

Edited By Robert Atkinson 2 on 02/10/2023 17:43:20

[Mark RandParticipant @markrand96270]

With 45Amps, you aren't going to get more than about 7hp. Drives Direct are egregiously overpriced, but they do source and modify a suitable device to make it do the job in a plug and play fashion. There aren't at all many 240-415V drives about because it's a tiny market segment. They seem to have almost given up selling off their own web site and do it all via fleabay nowadays.

This is what I've got and it does the job with my workshop. Max individual load for me is 2 1/2hp, but I do end up running a couple out of the five machines 3ph at a time reasonably often.

Edited By Mark Rand on 02/10/2023 17:46:12

[Ed Dinning 1Participant @eddinning1]

Transwave or similar switched capacitor units are probably your best bet. Some of these types work best with a pony motor (runs unloaded)/ balancer in circuit.

Possibly the lowest cost option too.

Note that they will nor run VFD's or any electronic gubbins, great with just a simple motor

Ed

[Clive FosterParticipant @clivefoster55965]

Robert

My Drives Direct box provides me with a neutral line and, with the smoothing inductors, works exactly like proper three phase supply save for the limitation on motor power that can be started. Drives Direct says 5 hp, half the VFD rated load, I reckon 3 hp is more realistic if the motor is connected to any sort of load.

So far as I can see or measure it behaves sufficiently like real three phase for anything I wish to hang on it to be perfectly happy.

Appears to be a little less demanding on the single phase supply than my friends Transwave rotary converter of similar rating.

I can only presume the doubling of price from Drives Direct relative to the standard Teco VFD covers the needed modifications to make everything safe, effective and not send interference back down the lines. I've no intention of opening it up and winding the clock back 40 odd years to when I was supposed to be some sort of electronics engineer to check. Over a decade of successful operation proves that something must be right as all the magic smoke is still successfully contained.

That said I'd not even dream of installing something like that without output smoothing. The radiated interference from driving a naked line doesn't bear thinking about.

I'd prefer a proper mains three phase but given that it seems to be impossible to find someone willing to connect up the three phase income I have the "interim" device has to soldier on. Newt so permanent as a temporary fix.

Clive

[Stuart Smith 5Participant @stuartsmith5]

A 3 phase generator would be my choice (sized to cater for the maximum starting current of your biggest motor). No matter what type of converter or vfd you got, you cannot get more out of your single phase supply than its capacity.

Stuart

[Robert Atkinson 2Participant @robertatkinson2]

Posted by Clive Foster on 02/10/2023 22:42:09:

Robert

My Drives Direct box provides me with a neutral line and, with the smoothing inductors, works exactly like proper three phase supply save for the limitation on motor power that can be started. Drives Direct says 5 hp, half the VFD rated load, I reckon 3 hp is more realistic if the motor is connected to any sort of load.

So far as I can see or measure it behaves sufficiently like real three phase for anything I wish to hang on it to be perfectly happy.

Appears to be a little less demanding on the single phase supply than my friends Transwave rotary converter of similar rating.

I can only presume the doubling of price from Drives Direct relative to the standard Teco VFD covers the needed modifications to make everything safe, effective and not send interference back down the lines. I've no intention of opening it up and winding the clock back 40 odd years to when I was supposed to be some sort of electronics engineer to check. Over a decade of successful operation proves that something must be right as all the magic smoke is still successfully contained.

That said I'd not even dream of installing something like that without output smoothing. The radiated interference from driving a naked line doesn't bear thinking about.

I'd prefer a proper mains three phase but given that it seems to be impossible to find someone willing to connect up the three phase income I have the "interim" device has to soldier on. Newt so permanent as a temporary fix.

Clive

The Drives Driect unit linked to by Mark Rand does not provide a neutral as standard. It requires an optional "neutral generator". Presumably a star transformer of some type and not just a resistor network. It also requires additional filters for some machines. Perhaps the unit you have included these. Unsurprisingly DD do not publish enough information to determine exactly what modifications they have done. Possibly none other than underrating it and setting for no or a very fast turn on frequency / voltage ramp. They certainly know how to charge for them though.
They now seem to sell only throgh ebay (odd for a "direct " company…) and currently don't list the required neutral generator or filters on ebay.

The 3-4 times underrating means that the 71/2 HP £3800 converter is not big enough for the OP task of a 4 HP load. He would need a 12 to 16 HP which may not be available. The 71/2 HP is stated as needing a 40A input supply so the larger one will presumably need a 80A feed, well above the OP's supply capacity.

Robert.

[clogsParticipant @clogs]

Thanks for the reply's…got some reading /studying to do…….

Just to add, at viewing of my new house the agent was asked to get a rough quote over the phone for a 3phs connection as it was the deal breaker…..

a 1000euro's was I thought very fair……see below….

when asked for a written quote once purchased it was 12,000euros…..

now the crazy thing is the supply pole is 10m from the meter and all the wiring is overhead…it has 6 huge wound wires that is the 3phase supply…..

Oh and right now were paying €2,20.per liter for D fuel……and a well used silent genny has just been advertised localy at over €6,000…….so thats a non starter, if you pardon the pun……

agin many thanks……..

[not done it yetParticipant @notdoneityet]

John/Frank,

There seems to be some discrepancies with at the thread on at least one other forum.

Is 5HP or 4HP largest motor? Will only one drive really be used at any one time (not entirely clear on the other one)?

Problem is not really complicated . Buy a 5HP VFD and accept that there will be no programmed protection for smaller motors. That way you have variable speed option for the one single motor in operation, but the VFD would need to be switched off between motor selection?

A non-variable converter should be cheaper than a VFD.

IF all the motors could be changed to delta (from star), thus allowing 230V operation, a cheaper converter could be purchased.

The alternative would be running those motors in star confiuration @ 230V and taking a 1/3 motor power availability hit.

With only needing one large 5HP inverter, if all the smaller motors (down to 1/5HP) could be changed to delta, you could likely buy discrete units, for each and every one, for rather less than a grand and be able to programme each for the safety/overload features? 3 HP VFDs seem to be a popular size, providing the optimum value per HP capacity?

I am running 5 (mostly cheap chinese) inverters in my workshop. Obviously purchased at earlier prices ( but some are likely cheaper now). Largest is/are 2.25kW and smallest is about 250W (I think). Certainly less that £500 outlay 

Edited By not done it yet on 03/10/2023 08:42:50

[Mark RandParticipant @markrand96270]

Posted by Robert Atkinson 2 on 03/10/2023 01:11:30:

 

The Drives Driect unit linked to by Mark Rand does not provide a neutral as standard. It requires an optional "neutral generator". Presumably a star transformer of some type and not just a resistor network. It also requires additional filters for some machines. Perhaps the unit you have included these. Unsurprisingly DD do not publish enough information to determine exactly what modifications they have done. Possibly none other than underrating it and setting for no or a very fast turn on frequency / voltage ramp. They certainly know how to charge for them though.
They now seem to sell only throgh ebay (odd for a "direct " company…) and currently don't list the required neutral generator or filters on ebay.

The 3-4 times underrating means that the 71/2 HP £3800 converter is not big enough for the OP task of a 4 HP load. He would need a 12 to 16 HP which may not be available. The 71/2 HP is stated as needing a 40A input supply so the larger one will presumably need a 80A feed, well above the OP's supply capacity.

Robert.

Where are you getting the 3-4 times unde-rating from??? The Teco VFDs that DD use have a 150% for 1 minute overload rating. DOL Starting a 4hp motor from a 7.5 hp rated VFD is no problem. The 'extra work' that DD do is to modify them to use a voltage doubler rather than a three phase bridge rectifier. I don't know whether they uprate the smoothing capacitors, but they might.

I do use a sine wave filter and delta/star grounded neutral generating transformer with mine, because I was already using them with a second hand Danfoss 23kVA VFD that I had used in the same role. That one was fed from a single phase step up transformer. But, in fact, very few three phase machines need the neutral, just a ground connection.

I have also re-programmed mine slightly and connected a time delay relay to the run signal contacts. This is so that it can live happily in the electronics/computer cupboard in the shed and automatically start when powered up from the switch on the wall. The VFD which gives variable speed for the dust extractor is similarly connected, but with control via a switched potentiometer.

 

I think that Clive and my experience of using the things trumps scare stories made from whole cloth…

 

Edit to add:-
I do wish that I had gone with Western Power Distribution's 2005 quote of £1.400 to replace the house's single phase supply with three phase. Trouble is that building the shed had already put me deeply in debt (it cost more than the bl***y house did!). Had I done that, I could plan for more solar panel/inverter capacity than now and for a fast charger for if we live long enough to get an EV. I did run 3ph cable from the breaker at the supply entrance to the shed, so that bit's done.

I might still do it at some time in the future, but only for the latter needs. The shed doesn't absolutely need it now.

Edited By Mark Rand on 03/10/2023 09:13:13

[Stuart Smith 5Participant @stuartsmith5]

John

From your profile I presume you are in Greece, so the application process / costing for a 3 phase upgrade might well be different from the UK, but here the cost will depend on the work required.

It may be that the original 1000 euro guesstimate was based on a nominal power requirement, while the 12000 euro will presumably be based on you filling an application form in with your requirements. If this is the case, it may be that the price is a lot more because for instance the transformer needs to be changed. If this is the case, it may be worth asking what the maximum power and starting current you could have on the existing. They may have assumed that you want to run all your machines at the same time for instance.

Stuart

[Robert Atkinson 2Participant @robertatkinson2]

Posted by Mark Rand on 03/10/2023 08:57:57:

Posted by Robert Atkinson 2 on 03/10/2023 01:11:30:

The Drives Driect unit linked to by Mark Rand does not provide a neutral as standard. It requires an optional "neutral generator". Presumably a star transformer of some type and not just a resistor network. It also requires additional filters for some machines. Perhaps the unit you have included these. Unsurprisingly DD do not publish enough information to determine exactly what modifications they have done. Possibly none other than underrating it and setting for no or a very fast turn on frequency / voltage ramp. They certainly know how to charge for them though.
They now seem to sell only throgh ebay (odd for a "direct " company…) and currently don't list the required neutral generator or filters on ebay.

The 3-4 times underrating means that the 71/2 HP £3800 converter is not big enough for the OP task of a 4 HP load. He would need a 12 to 16 HP which may not be available. The 71/2 HP is stated as needing a 40A input supply so the larger one will presumably need a 80A feed, well above the OP's supply capacity.

Robert.

Where are you getting the 3-4 times unde-rating from??? The Teco VFDs that DD use have a 150% for 1 minute overload rating. DOL Starting a 4hp motor from a 7.5 hp rated VFD is no problem. The 'extra work' that DD do is to modify them to use a voltage doubler rather than a three phase bridge rectifier. I don't know whether they uprate the smoothing capacitors, but they might.

I do use a sine wave filter and delta/star grounded neutral generating transformer with mine, because I was already using them with a second hand Danfoss 23kVA VFD that I had used in the same role. That one was fed from a single phase step up transformer. But, in fact, very few three phase machines need the neutral, just a ground connection.

I have also re-programmed mine slightly and connected a time delay relay to the run signal contacts. This is so that it can live happily in the electronics/computer cupboard in the shed and automatically start when powered up from the switch on the wall. The VFD which gives variable speed for the dust extractor is similarly connected, but with control via a switched potentiometer.

I think that Clive and my experience of using the things trumps scare stories made from whole cloth…

Edit to add:-
I do wish that I had gone with Western Power Distribution's 2005 quote of £1.400 to replace the house's single phase supply with three phase. Trouble is that building the shed had already put me deeply in debt (it cost more than the bl***y house did!). Had I done that, I could plan for more solar panel/inverter capacity than now and for a fast charger for if we live long enough to get an EV. I did run 3ph cable from the breaker at the supply entrance to the shed, so that bit's done.

I might still do it at some time in the future, but only for the latter needs. The shed doesn't absolutely need it now.

Edited By Mark Rand

The 3-4 times de-rating is wht DD specify when using the unit as a 3 phase converter NOT as VFD. The OPis looking for a converter.
The difference is because there is no "soft-start" ramp up of voltage and frequency.

[Mark RandParticipant @markrand96270]

3 times load with a 50% overload capability gives a 2 times de-rating for the drive, which is what they specified. No one using this sort of drive is going to be driving a Lumsden grinder or similar.

Edited By Mark Rand on 04/10/2023 01:24:06

[Robert Atkinson 2Participant @robertatkinson2]

That is not what DD say. Quote :

"All this range of DIGITAL Plug and Play Converter allow you to take a 150% overload for 30 seconds so the 6HP starting requirement of the 2HP mill can be accommodated by this 7½ HP converter"

So they say to use a 71/2 HP inverter for a 2 HP motor i.e. > 3 times de-rating.

https://www.ebay.co.uk/itm/154157588494

Robert

[Clive SteerParticipant @clivesteer55943]

My take on this thread is that if you want simplicity, in both installation and use, then a passive static converter is a good contender. The main components are just an auto transformer to convert 240V to 440 V which powers 2 of the 3 phase wires and a bank of capacitors to "generate" power on the 3rd phase wire. They are robust although not necessarily efficient but are very easy to fix by oneself or an ordinary electrician.

Their common failure mode is that the capacitors degrade with time but it is relatively cheap to replace a set for £50.

Adding a motor to turn it into a rotary converter improves the phase balance and provides a degree of energy storage beneficial for starting machines with direct on line motors. The downside is that the motor adds a level of noise and inefficiency. Static converters are reasonably tolerant of supply issues that some countries power distribution systems may provide.

Active 3 phase converters can be more efficient and compact but may need to be overrated to allow for DOL motor startup loads.

Converting each machine to be driven by a VFD is the most complex option. For those wishing to benefit from the variable speed they provide this is a price worth paying.

CS

[martin haysomParticipant @martinhaysom48469]

Posted by Clive Steer on 04/10/2023 10:48:18:

Adding a motor to turn it into a rotary converter improves the phase balance and provides a degree of energy storage beneficial for starting machines with direct on line motors. The downside is that the motor adds a level of noise and inefficiency. Static converters are reasonably tolerant of supply issues that some countries power distribution systems may provide.

could this be done by letting a machine not being used run.

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