Sensitivity to high voltages

GBDamo · Nov 21, 2017

The electronics within our machines are manufactured to be tolerant of 220V +/-10%. many components have a max 250V allowance.

Now we all know that although our domestic supplies are supposed to be 230V they can vary widely, I personally have measured 257V on one supply.

What in your opinion is the most cost effective way of limiting the supply voltage without causing the to trip due to high voltage conditions.

This is to protect a single device (~3-5 Kw) not the entire installation.

Any useful ideas appreciated.

Darkwood · Nov 21, 2017

You equipment should be tolerable of the voltages of the market it sells into, it is common to see voltages 240v - 250v, also the equipment if it is prone to mains transients it should incorporate it's own protective measures.
Are these machines ones you build yourself or just machinery you have on site?

PS if you have measured 257volts on a meter with true rms then you should report the findings to DNO, this indicates there supply in in breach of their own regulations currently 253volts, if you have a cheap meter then be weary of the reading been accurate.

Pete999 · Nov 21, 2017

GBDamo said:
The electronics within our machines are manufactured to be tolerant of 220V +/-10%. many components have a max 250V allowance.

Now we all know that although our domestic supplies are supposed to be 230V they can vary widely, I personally have measured 257V on one supply.

What in your opinion is the most cost effective way of limiting the supply voltage without causing the to trip due to high voltage conditions.

This is to protect a single device (~3-5 Kw) not the entire installation.

Any useful ideas appreciated.

Voltage stabiliser, UPS

GBDamo · Nov 21, 2017

darkwood said:
You equipment should be tolerable of the voltages of the market it sells into, it is common to see voltages 240v - 250v, also the equipment if it is prone to mains transients it should incorporate it's own protective measures.
Are these machines ones you build yourself or just machinery you have on site?

PS if you have measured 257volts on a meter with true rms then you should report the findings to DNO, this indicates there supply in in breach of their own regulations currently 253volts, if you have a cheap meter then be weary of the reading been accurate.

Thanks for the swift response, the equipment is "supposed" to be fit for purpose but we have one machine that is throwing up a protection fault code that indicates it has seen an overvoltage occurrence. This shuts the machine down and requires a manual reset. After multiple resets the fault becomes permanent and requires a replacement pcb.

We have two options in my mind, re-engineer to be more tolerant to overvoltage or install an up front voltage regulator but which product is best???

the Voltage was measured by a true RMS meter but not an expensive one.

GBDamo · Nov 21, 2017

Pete999 said:
Voltage stabiliser, UPS

Do you recommend any particular products??

Darkwood · Nov 21, 2017

With voltages measured that high I would first double check and get onto the DNO, last time I had 255v they were out within 2 hrs and came back next day to alter TX tapping, there is also the issue that this problem may not be a supply problem to your machine, there could be problems within your machinery that are spiking and blowing the PCB - if this is the case replacing the PCB will only possibly subject the new one to the same problems...
Without knowing what the machine is, its rating, how the PCB interacts with the rest of the machine etc it is impossible to advise on a solution as each scenario requires its own solution to suit. I take it your works in in close proximity to the sub station?

GBDamo · Nov 21, 2017

darkwood said:
With voltages measured that high I would first double check and get onto the DNO, last time I had 255v they were out within 2 hrs and came back next day to alter TX tapping,

Like I said, it was an inexpensive meter..

darkwood said:
....there is also the issue that this problem may not be a supply problem to your machine, there could be problems within your machinery that are spiking and blowing the PCB - if this is the case replacing the PCB will only possibly subject the new one to the same problems...

This is not only possible but quite likely, my request here is an attempt at grabbing a "low hanging fruit" solution. It may not be the most likely candidate but it is relatively cheap and easy to test hypothesis. Ruling out supply overvoltage gives a little more weight to to any push back we have with our supplier.

darkwood said:
Without knowing what the machine is, its rating, how the PCB interacts with the rest of the machine etc it is impossible to advise on a solution as each scenario requires its own solution to suit. I take it your works in in close proximity to the sub station?

I can't go into too much detail but essentially the PCB manages/inverts the power to a compressor using a TRIAC array. The manufacturer is adamant that it is only a problem in the UK hence why i'd like to rule out supply voltage.

As for the sub station, of those that have shown this fault many have been very close to pole mounted transformers but not sub stations.

Thanks for your thoughs.

Darkwood · Nov 21, 2017

If it is indeed close to a Pole Tx then it is a likely suspect, l have known close proximity be an issue especially nuisance tripping of earth leakage devices, when you say close proximity are we talking meter or a few hundred. You may be getting unwanted transients so the first thing would be fitting an anti surge unit and also ensuring the voltage is within limits, if your meter is True RMS then it should be fine to rely on assuming you get it calibrated regularly, if unsure use 2 meters and if they agree it tends to mean they are correct.
As you cannot provide info on the machine I cannot offer other solutions but would a small VSD not be an option, these will usually have integral filters, Triac Arrays are fine and a cheap solution but they have their disadvantages but lack info to comment further and appreciate if you cannot disclose.

GBDamo · Nov 21, 2017

darkwood said:
If it is indeed close to a Pole Tx then it is a likely suspect, l have known close proximity be an issue especially nuisance tripping of earth leakage devices, when you say close proximity are we talking meter or a few hundred. You may be getting unwanted transients so the first thing would be fitting an anti surge unit and also ensuring the voltage is within limits, if your meter is True RMS then it should be fine to rely on assuming you get it calibrated regularly, if unsure use 2 meters and if they agree it tends to mean they are correct.
As you cannot provide info on the machine I cannot offer other solutions but would a small VSD not be an option, these will usually have integral filters, Triac Arrays are fine and a cheap solution but they have their disadvantages but lack info to comment further and appreciate if you cannot disclose.

I know more info would make things easier so thanks for persevering.

By VSD do you mean voltage suppression device? and if so can you point me to a product that can handle 32Amp whilst clamping the output to 230/240V without tripping on overvoltage?
My googling has led me to £600-£1000 power conditioners but this seems like a massive sledgehammer for a tiny nut.

Darkwood · Nov 21, 2017

No, you express it runs a compressor so I make the assumption we are talking a motor, a VSD is a variable speed drive but i may be barking up the wrong tree here with the limited info', a drive would have built in filters usually and are more tolerant to input voltage ranges, it of course would mean altering the control of the machine and it would void any warranties and would have to meet machinery code standards.

static zap · Nov 21, 2017

GBDamo said:
..... The manufacturer is adamant that it is only a problem in the UK hence why i'd like to rule out supply voltage.
....
.

Are they comparing us to European 230 ... or usa 120 ?
Better dv/dt specced triacs are more expensive ...
So may be a price point thing ..while watching the pennies !

GBDamo · Nov 21, 2017

darkwood said:
No, you express it runs a compressor so I make the assumption we are talking a motor, a VSD is a variable speed drive but i may be barking up the wrong tree here with the limited info', a drive would have built in filters usually and are more tolerant to input voltage ranges, it of course would mean altering the control of the machine and it would void any warranties and would have to meet machinery code standards.

Yes, replacing integral components is a no go for the reasons you state hence me looking for an upfront device.

GBDamo · Nov 21, 2017

static zap said:
Are they comparing us to European 230 ... or usa 120 ?
Better dv/dt specced triacs are more expensive ...
So may be a price point thing ..while watching the pennies !

EU 230V, as for the components we can only assume you're correct but to be honest we don't even know which exact component on the PCB is failing.
If I can guarantee the incoming voltage is 230+/-10% I can kick the fault back to the manufacturer. If clamping the voltage cures the fault then it's just a matter of retro-fitting a suitable device.

Darkwood · Nov 22, 2017

It depends on the power demands of the machine but I would be looking to getting surge protection either a cheaper option at the machine or more costly one at the origin of your incoming supply. These will not limit voltage level as such but will absorb any spikes coming down the supply.

http://www.hager.co.uk/files/download/0/4540_1/0/Hager Guide to Surge Protection.pdf

dmxtothemax · Nov 22, 2017

Your voltage is supposed to be 230v ?
But is it in reality ? Ours is officially 230v but in reality it is 240v.
But that is still within the official margin of +10%.
most electrical appliances will handle even 257v.
But some sensitive electronics may not.
So if your mains varies that much then don't use sensitive
electronics that cannot handle it.
Apart from using a UPS there is no easy way out !
What are you having a problem with ?

Pete999 · Nov 22, 2017

GBDamo said:
Do you recommend any particular products??

I could if it was 10 years earlier, but years go on and technology changes, maybe if you looked up UPs and VS companies, explain the scenario and conditions they will be able to advise you. That's what I did and got some good kit, it was used overseas in countries where the supplies weren't reliable, and had no trouble, the VS firm could also diagnose over the phone or by email, the UPs was EMERSON but that's all I remember, hope my reply has been useful, one thing the VS kit was dead simple to connect, loan and supply.

One thing I did find with the UPs, if you are using any form of remote controls or sensing equipment, use a screened cable or twisted pairs to try and avoid voltage pick up, I had one install where the UPs was in a small room which needed to be Air Conditioned, ( it was in Asia so very hot) the customer required an emergency stop for the UPs, which involved a control pair, every time the AC started up out would go the UPs, took me a while to suss out that the control pair was picking up volts from the AC starting and tripped the UPs, worth noting, I think my detective work caused the supplier to add the proviso in their install manual. Clever git aint I?

Lucien Nunes · Nov 22, 2017

Stepping the voltage down with a bucking transformer is a simple and cheap solution if the maximum incoming voltage is high but the percentage variation is no more than the board's total tolerance. I.e., you don't need to stabilise, merely adjust your range of incoming voltages to align with the range the board will accept.

Suppose you find your supply only ever varies from 230-260V, while the board wants to see 207-253. You could reduce your midpoint 245V down to their midpoint 230V, making the max voltage 260-15=245V which is 8V within spec for the board, and your min 230-15=215V which is equally in spec. For a 3kVA device your bucking transformer has to knock 15V off the supply while handling 3000/215=14A, so a transformer of 15*14=210VA would do the job. In practice you would want to allow a bit more margin but you can get this for under £30 e.g. | 2 Output Toroidal Transformer, 225VA, 2 x 15V ac | - http://uk.rs-online.com/web/p/toroidal-transformers/6719034/

Primary across the mains, secondaries in parallel, in antiphase series with the load. Note that with a toroidal the secondaries may not be insulated from the exterior for the primary voltage - you might need to use extra insulating washers, or choose an EI-frame transformer instead. A regular autotransformer is ideal, especially if it has suitable taps to give you a bit of leeway, but the bucking method is usually by far the cheapest.

Note also that the board's method of measuring the voltage may not be the same as your true-RMS meter. It might have a basic method of measurement that is misreading high due to waveform distortion, even though your meter is giving a correct measurement.

GBDamo · Nov 22, 2017

Thanks for that. Will look into it and try to get my head round it all. Expect me back asking what it all means.

Marvo · Nov 22, 2017

Before throw large amounts of money at the problem I'd spend some time and effort establishing if there actually is one. I'd put a PQA on the supply and gather a few days or preferrable a week of data to establish the power quality and pinpoint precisely the issues.

Pointing a finger at power quality is a 'get out' that's often tried by suppliers to limit their warranty exposure when they're selling products that have high failure rates due to poor design or build quality. Having solid evidence will put the ball back in their court.