Supply required to power Digital Phase Convertor

[O'Chippy]

Hello all,
I'm a carpenter by training but having recently purchased a victorian house in need of significant refurbishment I have decided to assemble a workshop so I can produced millwork and joinery "in-house".
The 5m x 5m garage/shed that I will be setting up the workshop is located at the end of my garden and this garage may in time be demolished as part of the overall project.
Therefore the current power supply to the building (detailed and illustrated below) will not be upgraded.

I value old cast iron machinery and there being much greater choice of these machines in the 3 phase variety I'm considering if I could used a Digital Phase Convertor to provide 3 phase supply within the workshop.
I understand that the limiting factor will be my existing supply and was hoping someone may be able to comment on the suitable of my existing supply to power a DPC?

I will only need to power a single machine at a time and I am willing to forgo dust extraction (and it's power requirement) in this temporary workshop.
Power requirement wise, I'd like to have sufficient juice to power a Wadkin EQ 511 and associated power feed, similar to this machine
If the existing supply is not sufficient I will just have to settle for hobbyist grade machinery for the time being.


1: Sub fused board from incoming supply to supply cable to garage

2: ~70metre run of 20mm OD supply cable to garage:

3: Garage sub fuse board, currently 1no fuse for 13amp sockets and 1no fuse for a light

 

[Sideways]

You have 30A available from the incoming supply so you can get a sparky to add a 20 or 30A breaker and circuit in your garage. That's enough to drive a usefully sized DPC.
Very very crudely, if the DPC was about 50% efficient, you would be able to drive about 4kW max load across all motors. I would be investigating 3 and 4kW DPC's.

At first glance, the wadkin EQ looks to be a 5HP machine and marginal / too big for your supply when you add a power feed on top. How about a 1980's SCM T100 ?

 

[ChaiLatte]

It might be wise to unabbreviate your thread title. DPC is not a common term for the device of which you speak.

I clicked on the thread wondering why someone would want an electric damp proof course and am now thoroughly disappointed.

 

[RogerS]

You have 30A available from the incoming supply so you can get a sparky to add a 20 or 30A breaker and circuit in your garage. That's enough to drive a usefully sized DPC.
Very very crudely, if the DPC was about 50% efficient, you would be able to drive about 4kW max load across all motors. I would be investigating 3 and 4kW DPC's.

At first glance, the wadkin EQ looks to be a 5HP machine and marginal / too big for your supply when you add a power feed on top. How about a 1980's SCM T100 ?

Supply might be OK if the power feed is turned on after the Wadkin due to the startup surge on the Wadkin, surely ?

 

[O'Chippy]

Thanks @Sideways. This is what confuses me, if we expect 50% efficiency from the DPC and require 4Kw output do we then need a 8Kw "labelled" DPC: in my builder calculations (8Kw DPC x 50% efficeney outputs 4Kw).

 

[Spectric]

Digital phase convertors do not suffer the drawbacks of the digital invertors, you do not get variable speed but can have three phase distribution with multiple outlets . With an invertor is has to be oversized for a given load by at least 1.75 x and due to EMC is restricted on available power, with the convertor your only limit is on available power and there are no restrictions on output power so larger motors can be used. The biggest difference is that the convertor provides a 400 volt supply unlike the invertor that is 230 volts three phase and restricts your choice of motor, so with the convertor there are no modifications needed on the machine and any DC brakes work.

Being a digital device they can deliver 90 plus percent efficiency, get your installation inspected as that Wylex board looks very old, that switch below looks like it is from the seventies and determine the cable size to work out exactly what it can deliver in terms of power. You have shown one end of the supply but where is it derived from ?

On a 40 amp supply you can run Digital Phase Converter 7.5Kw/10Hp 240V in 400V Out - JFK Electrical

 

[RogerS]

.....You have shown one end of the supply but where is it derived from ? .......

Not a problem

 

[Spectric]

Yes exactly, you would not believe some people think using wire rated at 30 amps will just give then 30 amps even if connected with matchsticks to a socket.

 

[O'Chippy]

@Spectric from reading very informative previous post from yourself and others I'm satisfied that the VFD/invertor route is not for me. Too techy, Its DPC or I'll work with the existing 240v supply.

You are spot on regarding the Wylex board, although its probably one of the more modern components of the electrical installation.
The house will be getting an entire rewire, even the cutout/head/meter is getting pulled out and renewed and relocated. However there are no plans to upgrade the supply to the garage, it may be demolished in a year or so.

See below expanded photo of the cutout arrangement. There are even more ancient components outside of the frame which give it a certain Battersea Power station-esque vibe.
I cant inform you further on the cable other than its 20mm in diameter and ~70 metre long. There is no specification printed on the cable.

 

[O'Chippy]

Not a problem

View attachment 165056

That's just plain disrespectful. I'm a carpenter, not a shuttering carpenter.

 

[Spectric]

Just remembered something to be aware of, a lot of these convertors only give the three lines with no star point, I recall a pillar drill where it had a 230 volt lamp which was wired from line to neutral and could not be used with the convertor. Use a rechargable magnetic base LED lamp instead.

 

[Spectric]

although its probably one of the more modern components of the electrical installation

That is what we call add ons connected to add ons, looking at the age and incoming DNO cable it could be a 60 amp supply, these days we have 100 amp supplies.

If we assume that cable is three core and about 20mm OD then it could be 16mm, this gives a volt drop of 2.5mv per metre per amp so for every amp drawn over 70 metres it will lose about 0.35 volts. Remember the lose is in both the live and neutral . This would mean a tiotal load of 30 amps is pushing the limit and that 70 metres is why.

 

[Sideways]

Thanks @Sideways. This is what confuses me, if we expect 50% efficiency from the DPC and require 4Kw output do we then need a 8Kw "labelled" DPC: in my builder calculations (8Kw DPC x 50% efficeney outputs 4Kw).

Hi,
It's the internet. I can't give you detailed advice because there are a whole lot of "it depends" questions in the way.
Things are never quite as good as you would like them to be.
The DPC has efficiency losses.
Motors have efficiency losses.
Motors have power factors that mean you have to supply them with more current than you would expect from a simple Power = Amps x Volts that would be true for a simple electric heater but isn't when it comes to motors.
All these losses multiply up hence the crude advice to "halve it".

Also, a VFD supplying a single motor can soft start the motor and very effectively limit the startup surge so that it never needs to exceed the full load current if you want it that way.
A DPC feeding multiple motors can't do that and they are specified typically so that the largest single motor is about 2/3 the power of the DPC total rating.

You need a sparky to install the new breaker in your garage consumer unit, get one who does industrial work (not a domestic installer) and have them look at the specs of DPCs for you. There is no harm in putting a bigger one in - it means the components will be running a bit below their limit and will run cooler and last longer. In fact with the Chinese DPC's I recommend going at least 1 size up, but that doesn't mean you get to use that extra. Your supply is the limiting factor. Like the road and 70mph speed limit are even if you have a 2 litre car good for 130mph.

 

[O'Chippy]

@Sideways & @Spectric many thanks for your comments, really helped me decide what route to go.

I think for now I should stick with assembling 240 volt machines, maybe get a 16amp circuit installed but forget about having 3 phase in the garage.
There are too many variables with the existing installation and its not a field I'm very inclined to study, besides the exsisting installation itself will be striped out and upgraded and even the garage may be gone in a year or two.

I think I should instead focus on 240 volt machinery and scrap the idea of a getting a spindle moulder at this time. I have a trend router table and good 1/2" matkita router, which will suffice moulding requirements, grant it at a lower production speed.
Planer thicknesser purchase similarly will go on hold replaced by a 6" Jet/Axi 240volt jointer and a separate benchtop thicknesser both which are plentiful on the used market.

 

[HOJ]

the cutout/head/meter is getting pulled out and renewed and relocated

If you move it try and keep it as a 3 phase head, my biggest fopar was to let mine go when I moved ours, I was quoted nearly £4k to to put a replacement 3 phase service in.

 

[Ttrees]

Can you not de-rate motors with a digital phase converter, like you can with a VFD...
(one which has this feature, that is)
For the spindle moulder, or other machine which has only one motor,
whilst taking lighter cuts obviously, with say a hand cranked powerfeed?

Cheers folks
Tom

 

[O'Chippy]

If you move it try and keep it as a 3 phase head, my biggest fopar was to let mine go when I moved ours, I was quoted nearly £4k to to put a replacement 3 phase service in.

There is a 3 phase head but there is not a 3 phase supply.
I'm actually going to get back in contact with the ukpn engineer (who did previously did a site visit) and request a quotation to install a 3 phase supply when the cutout is moved to its new location.

 

[HOJ]

There is a 3 phase head but there is not a 3 phase supply.

Is it a 4 core cable though, may not be live, but still wired back to a link box in the street.

 

[O'Chippy]

Is it a 4 core cable though, may not be live, but still wired back to a link box in the street.

IIRC the UKPN engineer said it was a three phase head but the cable is not 3 phase.
I know you can see a "4 head"? but I think that was just used regardless of the cable.
I'll have to confirm with the engineer

 

[HOJ]

Worth checking, the DNO wouldn't normally put a head in that isn't cable connected.