Control Transformer

[Richard3009]

Looking for a 240v /110v control transformer, all in needs to do is drive 10 relay coils, typically what size would be specified for a panel to be built

 

[Besoeker]

We normally use 500VA units as a minimum.
But then the control circuit is a fairly insignificant part of the total power consumption for us.

BWS is a good source.
But I'll be looking for my commission...........

01527 833033

 

[Knobhead]

Not enough information. 500VA is liable to be way over sized, you need to calculate the loading.

 

[Besoeker]

Not enough information. 500VA is liable to be way over sized....

But in the context of a 3MW variable speed drive......

 

[Bobster]

But in the context of a 3MW variable speed drive......

Then I'd say you've probably undersized it.

 

[Besoeker]

Then I'd say you've probably undersized it.

On what basis?

 

[Bobster]

The amount of cooling fans, etc... would quite quickly eat that up.

The last 2MW VSD install I designed used a 1500va 110tx and a 5A 24VDC PSU.

 

[Knobhead]

RoB’s seen pictures of a furnace I redesigned, the control transformer was 5KVA.

You can’t just come out with a glib statement of 500VA will suffice.

 

[Besoeker]

You can’t just come out with a glib statement of 500VA will suffice.

Nor would I.

 

[Deleted member 72666]

As Tony as pointed out you need to know what the inrush currents these relays take, add them together then choose the nearest size up from that, don't forget to allow for future expansion.

 

[Besoeker]

The amount of cooling fans, etc... would quite quickly eat that up.

The last 2MW VSD install I designed used a 1500va 110tx and a 5A 24VDC PSU.

Depends on what you use the 110V for.
Regardless of actual drive voltage, we'd normally have a 400V three phase four wire auxiliary supply.
We need that for the electronics anyway.
Items like fans and anti-condensation heaters derive their power from that. The 110V is used primarily for control relays.

I'm not suggesting for a moment that we always use a 500VA transformer. Just that we don't normally use anything smaller.

 

[Bobster]

As for the OP, 250va will do.

 

[Knobhead]

OK we don’t know what the OP is proposing to use. If they are octal base relays a 500VA transformer will dwarf the rest of the gear and cost many times more.

 

[Besoeker]

OK we don’t know what the OP is proposing to use.

Nail on head.

 

[Knobhead]

So why even mention 500VA?

 

[Besoeker]

So why even mention 500VA?

Because that is generally the minimum size we use.
And that's what I posted.
Not an assertion that it was the right size. For anything.
Scroll back sunshine.

 

[Knobhead]

1. I’m anything but sunshine.
2. If you noticed I told the OP to calculate the loading.
3. I don’t post spam, re post #2.
4. Unlike you I didn’t give totally irrelevant information. What you stock in your stores is up to you, it has no bearing on the OP’s question. I would add I could go in to our stores and come out with a transformer anywhere between 10VA and 2MVA.
5. Unlike you I’m not a salesman. I note you didn’t give any real figures when asked about payback periods for energy saving.

 

[Besoeker]

I’m anything but sunshine.

No dispute with that.


​

If you noticed I told the OP to calculate the loading.

Good advice. No dispute with that either.

Unlike you I didn’t give totally irrelevant information.

It was a passing comment on what we do and the information wasn't, as you suggest, totally irrelevant. I gave contact details for a UK supplier of good repute.

What you stock in your stores is up to you, it has no bearing on the OP’s question.

And I made no comment about what we stock so your comment is an irrelevance.

Unlike you I’m not a salesman.

Unlike you, I make no presumption about your occupation.
And, just for the record, your presumption about me is incorrect.

I note you didn’t give any real figures when asked about payback periods for energy saving.

Interesting comment.
Much of my professional life has been in the power electronics industry and mostly variable speed drives.
Energy saving is a major driving force, particularly for fans an pumps. I'm sure you understand the cube law relationship between speed and power.

Often, when we bid a job, we are required to provide guaranteed efficiency figures at the bid stage. Usually NNT.
Make it safe and too low and lose the job. Make it too high and fail to meet the claim, even by half a percent, and get walloped with crippling financial penalties. You know this going in. Getting the numbers wrong isn't an option.

Because of such requirements, I have put a lot of effort into mathematically modelling variable speed drives - the supply transformer, the power electronics, and the motor. Serious number crunching. Some bits of programming I've written.And sometimes a but of humour injected.

Sub Plonker()
Title = "Not a valid entry !"
Msg = "Number of poles must be an even integer e.g. 2, 4, 6 etc. Try again."
Style = vbCritical + vbDefaultButton2
R = MsgBox(Msg, Style, Title, Help, Ctxt)
End Sub.

 

[Darkwood]

Absolutely no disrespect Besoeker but one key factor any green company always fail to inject into their calcs is technology becoming mainstream in a sense that when mass production follows the prices crash as in other threads even before your membership I have over and over again pulled the verbial rug from under such claims ....yes at the time of writing a saving is as good as the ink its printed in but factor in depreciation of material costs over the years then all of a sudden you find if companies delay the expense of switching to the green/energy saving option until the market has settled they actually gain more in savings ... this model is classic and repeats generation after generation but except those designing the set-up all employees and customers are easily misled... all new technology regarding energy efficiency is usually over costed to start by a large margin until market trends bring it down.

Now if your offering a patented product that is unique and cannot be legally copied and gives large savings then I'll listen but this is not the usual model most green companies are just becoming the 'middle man' for as long as they can while the industry gets used to a new product, thowing calculations and percentages means nothing to the customer if he has to run for 5yrs to get a return because by then the prices of the energy saving goods falls to a point where waiting is the best option to save money but only as long as they still make the move eventually.

The trend of Energy efficient materials actually goes against the grain of inflation and average rise and fall of goods in that the initial competition is fierce and this ensures a fast price fall over several yrs.

So the question is do you factor this in and can you give an example that reflects the real depreciation of the product over the money saving term?

 

[Besoeker]

Now if your offering a patented product that is unique and cannot be legally copied and gives large savings then I'll listen

Then perhaps I have something for you to listen to.
Unique certainly. We are not making widgets. Power electronic equipment, mainly variable speed drives. Some quite big ones by most standards. Upwards of 1MW and typically 3.3 kV or 11kV. And we make these from component level. We are not "middle men".

Not your average variable speed drive. Either in terms of ratings or configuration.
They are designed to give very high efficiency and much lower harmonics than other variable speed drives,

Large savings? Well, that would depend on how you quantify large. On one site, the difference between in fixed speed (built in facility for that) and in variable speed for one of the drives is about £40,000 a month. For others it's more, or considerably more. We have some in a petrochem facility. Non-operation of these, even for a few days, affects GDP.
Mass produced? Not hardly.

The trend of Energy efficient materials actually goes against the grain of inflation and average rise and fall of goods in that the initial competition is fierce and this ensures a fast price fall over several yrs.

The energy efficiency I mentioned is not about the materials used. It's in the design and operation of the system. As I said in an earlier post, we have to provide guaranteed overall efficiency at the bid stage. Getting it wrong isn't an option. We're talking big numbers both in terms of energy losses and financial pain. Mostly, the drives have efficiencies above 99% and the overall system including both the motor and drive is better than 95%.

That said, the majority of the materials can be recycled. Steel, copper, aluminium.

Hey ho.....
How did we get here from control transformers..........