Avr Vs Step Up Transformer

[gouda]

hi

went looking for a 2kw automatic voltage regulator (voltage drops to 170V) for the 18000BTU a/c a few days ago. The local electrical shop showed us the step up transformer which had 60A marked on the front and cost about 9000Baht, suitable for the whole house supply i presume

Said they didnt stock the AVRs as they dont last as long as these.

Anyone know what the pro's and cons of each are.. and how would you hook up a step up transformer as its not automatic i presume

TIA

[tjo o tjim]

Step-up transformer is best if the voltage is always low at the same level. If the voltage fluctuates up and down then you need an AVR.

[Crossy]

Care is required, if you try to boost your 170V to a full 220V what happens should the reason for your low voltage be fixed? 284V is what!! Bye-bye technology, light bulbs etc etc

A fixed transformer that boosts by about 10% may be a solution (170V in to 187V out), you'll likely still need an AVR for sensitive equipment but at least you'll not fry anything if the input achieves 220V (244V out).

Don't forget, you never get something for nothing, so a 10% increase in voltage on the output side will mean a 10% increase in current drawn from the input side.

Any indication of the ratio of this transformer in your local shop?

[gouda]

thanks for your replies

i went back to the shop to get a better description of the thing.

actually the unit is a step up/down transformer with a big knob on the front with steps 0 to 8 or so and a analogue dial on the front showing the voltage output.

you turn the knob until the output reaches the desired voltage. if the output voltage goes over 220 it will beep continuously until you turn the knob down

have many models with diff current ratings 15,20,30,60A

sounds quite convenient if a single unit can be used for an entire house.. as opposed to separate AVRs for each equipement

although dont want to risk damaging A/Cs and other electronics...

am at the end of a power line with regular brownouts to 170V , if the voltage goes back up will it jump straight to 220V and fry my equipement or slowly to give me a channce of stepping down the transformer?

[tjo o tjim]

Automatic is much better, but typically under-voltage is worse for motors and over-voltage can become more dangerous for people and can damage some electronics.

On the islands, the manual voltage regulators are common, and work well if a big part of your load is incandescent lighting and not supported by the voltage regulator. For low-voltage, the bulbs will just not be as bright, but you still get some useful light out of them. They are considered a "linear" load-- voltage goes down, current goes down, power goes down.

Today, most of your loads are either inverse characteristics (lower voltage = higher current, like a TV or PC), or voltage critical like a motor. This makes a whole-house voltage regulator kind of a "race to the bottom" where you just make the problem worse for your neighbors by increasing your current demand. Increased current = increased voltage drop on the power lines = lower input voltage for everyone.

But... there isn't much else you can do if the voltage fluctuations are causing you to burn out bulbs, motors, and electronics.

Since voltage usually recovers in the early morning, not getting up early to adjust the manual voltage regulator could cause problems. You should be able to find an AVR big enough to supply the whole house; it is basically the same as the manual unit with a few extra controls.

[lopburi3]

The Thai made transformers used to be way over rated and suspect they still are. I would buy on basis of half the faceplate rating. That said they do work well if you are always low. You might also consider buying - or better yet buying with others - a new transformer to feed your home. That 18k air conditioner is not upcountry electric friendly.

[elkangorito]

Care is required, if you try to boost your 170V to a full 220V what happens should the reason for your low voltage be fixed? 284V is what!! Bye-bye technology, light bulbs etc etc

A fixed transformer that boosts by about 10% may be a solution (170V in to 187V out), you'll likely still need an AVR for sensitive equipment but at least you'll not fry anything if the input achieves 220V (244V out).

Don't forget, you never get something for nothing, so a 10% increase in voltage on the output side will mean a 10% increase in current drawn from the input side.

Any indication of the ratio of this transformer in your local shop?

I totally agree with Crossy (see bolded & underlined above).

In the case of motors, a decrease in voltage will mean an increase in current. If your supply is the problem (not enough "amps" availability), AVR's are no good as they will use more current as the voltage decreases.

At the end of the day, you need to know why your voltage is fluctuating. Is it because of transformer load? Is it because you have undersized "mains"? Is it because the PEA/MEA has not upgraded their high voltage supplies to transformers?

There are many possibilities & until you know the reason for your problem, any money spent could simply be a waste.

[gouda]

Care is required, if you try to boost your 170V to a full 220V what happens should the reason for your low voltage be fixed? 284V is what!! Bye-bye technology, light bulbs etc etc

A fixed transformer that boosts by about 10% may be a solution (170V in to 187V out), you'll likely still need an AVR for sensitive equipment but at least you'll not fry anything if the input achieves 220V (244V out).

Don't forget, you never get something for nothing, so a 10% increase in voltage on the output side will mean a 10% increase in current drawn from the input side.

Any indication of the ratio of this transformer in your local shop?

I totally agree with Crossy (see bolded & underlined above).

In the case of motors, a decrease in voltage will mean an increase in current. If your supply is the problem (not enough "amps" availability), AVR's are no good as they will use more current as the voltage decreases.

At the end of the day, you need to know why your voltage is fluctuating. Is it because of transformer load? Is it because you have undersized "mains"? Is it because the PEA/MEA has not upgraded their high voltage supplies to transformers?

There are many possibilities & until you know the reason for your problem, any money spent could simply be a waste.

I don't know the technical reason why, I thought it was just due to attenuation as apparently we're at the end of the power line. When getting our meter we were told by the PEA that this could be a problem.

Actually haven't measured the voltage drop personally but the air con installer said it dropped to 170V when one of the 3 18BTU a/c's is switched on. The A/C is not cold even set at 19C and the UPS starts beeping . Also when other high current items are in use e.g ARC welder the UPS beeps and lights flicker.

I was hoping the AVR would be a solution as have installed A/Cs at only use them at night when it seems there is no problem i.e. UPS doesn't beep

I thought these low voltages at end of power lines were quite common and an AVR would fix it, otherwise would be rather disappointed in having spent 84K on installing 3 a/c's

does any of the above info suggest an AVR would work?

[elkangorito]

A voltage drop when extra load is applied can mean;

1] Your Consumer Mains cable is too small.

2] There is a resistive problem somewhere in your electrical installation (although I think this is not the case here).

3] Your supply transformer is loaded to the max (highly likely).

Points 1 & 2 can be solved by you.

Point 3 is the responsibility of your electricity provider.

If point 3 is your problem, an AVR will not help you. Why? As the voltage falls, it uses more current to make up for the lost voltage. If extra current is not available, it will not be able to boost the voltage.

[elkangorito]

A voltage drop when extra load is applied can mean;

1] Your Consumer Mains cable is too small.

2] There is a resistive problem somewhere in your electrical installation (although I think this is not the case here).

3] Your supply transformer is loaded to the max (highly likely).

Points 1 & 2 can be solved by you.

Point 3 is the responsibility of your electricity provider.

If point 3 is your problem, an AVR will not help you. Why? As the voltage falls, the AVR uses more current to make up for the lost voltage. If extra current is not available, it will not be able to boost the voltage.

Edited August 18, 2009 by elkangorito

[technocracy]

Had exactly the same problem here in Vientiane. We were end of line and even though we had 3 phase meter none of the phases had sufficient juice to fire up our main 24k btu aircons compressors. Sure they run the fan but the compressor needs a large amount of ampage to start it up.

I guess the power will fluctuate depending on the time of day? Our power varied between 170 and 220 depending on the time of the day however even when at 220 there just wasn't the available ampage to fire up the compressor. I highly expect that the transformer for your village is way over subscribed.

Our solution . . . 50kva transformer link directly to the high lines and everything is perfect!

Edited August 20, 2009 by technocracy

[elkangorito]

I highly expect that the transformer for your village is way over subscribed.

Our solution . . . 50kva transformer link directly to the high lines and everything is perfect!

Did you pay for the txer?

I don't know the situation in Laos but the MEA/PEA in Thailand are supposed to pay for any problems in the system. There appears to have been far too many foreigners who have been conned by the electrical authorities, when clearly the authorities should have paid.

In the case of the OP & if his problem is that of an overloaded supply transformer, the PEA MUST pay.

There are few exceptions to this.

[gdhm]

I highly expect that the transformer for your village is way over subscribed.

Our solution . . . 50kva transformer link directly to the high lines and everything is perfect!

Did you pay for the txer?

I don't know the situation in Laos but the MEA/PEA in Thailand are supposed to pay for any problems in the system. There appears to have been far too many foreigners who have been conned by the electrical authorities, when clearly the authorities should have paid.

In the case of the OP & if his problem is that of an overloaded supply transformer, the PEA MUST pay.

There are few exceptions to this.

You are correct BUT the reality is that (as with us who have been pushing for 10 months) is evasion, obstruction in seeing senior officials, lies unfortunately, always being offered the "if you want it done quickly you can pay", if you want us to do it then you must wait for the budget to be approved and the queue ahead of you to be dealt with first of course.

When we say we will not pay we are entitled to an adequate supply and so is everybody else on our line (184V down to 175V at night, oscillating by the second at times during the day and occasionally 219V around 10am is not acceptable be any standards. and yet they continue to bring new houses on line and have been aware of the problems BEFORE we raised the issue last November. Budget and queue is the favourite (possibly truthful excuse) and hard to fight as it is impossible to know the validity of the argument. We live in Khon Kane City so hardly out in the sticks.

Of course if they keep queue jumping with privately paid jobs from frustrated clients (fed up or unable to wait longer)then the queue will never reduce and only increase.

Dave

[gouda]

well i went to zeer rangsit a few days ago as mentioned in another thread on AVRs . Could only find 1 shop which stocked these, called NPE or something like that and sells lots of electrical components.

They had 2 brands one called Silicon and another which i've forgotten but didnt look as good.

They had a 500VA @ 2500B, 2000VA @3800B, 3000VA@4500B, 5000VA@7300B, 8000VA@12700B, 10000VA@16000B

would have got one to try but don't think I'll bother now given the info above...

Have already been to the PEA and guess will have to wait for them to install another transformer closer to us..... will have to put up with the heat in the meantime!!!

[technocracy]

I highly expect that the transformer for your village is way over subscribed.

Our solution . . . 50kva transformer link directly to the high lines and everything is perfect!

Did you pay for the txer?

I don't know the situation in Laos but the MEA/PEA in Thailand are supposed to pay for any problems in the system. There appears to have been far too many foreigners who have been conned by the electrical authorities, when clearly the authorities should have paid.

In the case of the OP & if his problem is that of an overloaded supply transformer, the PEA MUST pay.

There are few exceptions to this.

Yes I paid - that's the way it's done over here, basically if you want a decent power supply you pay for a transformer. 3 years later and nothing has changed on the village transformer, this I know from the wifes friends who are connected to the normal supply.

In the end it was a pretty expensive outlay but it's worked out far better than relying on the village one, since we obviously don't get effected when ever that transformer has problems. So sometimes we're the only house in the village with power.

From reading the figures quoted on here for them in Thailand it was was positively cheap incomparison - all in a working around 150k baht ~ $4500 (if I remember rightly) that is a 3 phase 50kva transformer as well - not single. I think I've seen figures around 325k for similar in Thailand?

[tjo o tjim]

Hands down, if you have the means, it is best to pay for an upgrade to the transformer. Communally, upgrading a village transformer is the best use of resources (given minimum transformer sizes), but doesn't guarantee you long-term problem resolution. Resource constraints for PEA/MEA are one thing... but if you have the means, help fix the problems.

[technocracy]

Hands down, if you have the means, it is best to pay for an upgrade to the transformer. Communally, upgrading a village transformer is the best use of resources (given minimum transformer sizes), but doesn't guarantee you long-term problem resolution. Resource constraints for PEA/MEA are one thing... but if you have the means, help fix the problems.

Have you seen the prices of 150Kva and larger Transformers?!?!

Also if you are already at the end of the line you still be getting the dregs and if any more houses are built in between you and the transformer you could be back to square one even after shelling out cool 1/2 or 1 million baht or so for the priviledge!

It might seem selfish but hey if you have the means just get the transformer you need to run your house and let the rest squabble over whenever PEA are going to upgrade the other.

One of the major point about having your own transformer is that you can ensure it is professionally install and the has a proper MEN and don't have any possible Somchai butchering something in between you and the transformer. On my local transformer I was seeing 50v on the neutral and at some points over 100v! There must of been some seriously dodgy wiring and equipment some where along the the way before it reached my house. Now I have a correctly installed transformer with 0v on Neutral and a constant 230v to go with my european standard wired house.

[gdhm]

Well our man in the PEA is trying a different approach when we said NO WAY for a transformer they should be sorting out.

"Oh no not a transformer. You are about 200m from a transformer. we will run a line just for your house form that transformer to you house (around 15000 baht).

We are still holding out on a new phasee being added as his boss said no it is OUR (PEA) responsibility and that solution would only help us not the rest of the affected soi(s)

[elkangorito]

Maybe information on this website can help you? Explore all of the menu options.

http://www.pea.co.th/th/eng/

In the meantime, don't pay for anything. As a matter of fact, you may like to try telling them that you will not pay for any electricity that is "unreliable". Mind you, I would reinforce this by saying that "my lawyer will follow up your 'service policy' (see PEA link). Maybe this will work...maybe not.

Getting back to the real issue, your load is obviously too great for your supply.

I therefore suggest that you minimise load at the worst times, although I guess that you have already done this.

In the worst possible scenario, the high voltage supply (22kV+) to your area is inadequate. This could mean a long wait for the PEA to "upgrade" their high voltage lines. If this is the case, any money you spend on trying to obtain a "reliable" supply is wasted money.