Shell Type Transformer Not Performing as Expected on Low Power Input

How did you come to know the type, size and number of windings to use?

Why do you think it should be more powerful?

i have use this ratio to help me in the process. ie. V1/V2=N1/N2=i2/i1 it is powerful cause at full working input voltage 240 or 230 or 220 volt i get a max 7 volt drop on the secondary.

What is 190 squared divided by 240 squared, multiplied by 10000 watts, Mildred?

" an auto transformer would not work, the up and down power pulled from it would burn it up"

Actually rewinding your unit you have noe wot work as a auto transformer would work just fine. Your cheap one like burned out because it was way too small. Also working in an autotransformer configuration it would only have to handle around half the wattage instead oteh full wattage which would free up a considerable amount of reserve power.

If you would go that route I would recommend making the taps on the primary end of the windings and give yourself something like 10 volt input steps from as low as 160 volts on up while placing your 120 volt tap closer to 125 or 130 at no load.

Replying to Comment by tcmtech"If you would go that route I would recommend making the taps on the primary end of the windings and give yourself something like 10 volt input steps from as low as 160 volts on up while placing your 120 volt tap closer to 125 or 130 at no load."

"so what you are saying is that i would get a better performance stepping up the input voltage"

How much reluctance is in this core? How much eddy current losses do you have? At what magnetic flux density (B or H) will this core saturate? Is this an air gap in this core? (Sorry, I already asked that.) Have you reviewed the basics of magnetic theory for a transformer before lumping iron sheet metal and varnish coated wire together?

you need this first

If the power isn't there you can't create it.

I've had fuses (fencing wire) glowing red hot when connected to a low peak power rural reticulation network with my AVR faithfully giving steady output and the insulation dripping off the supply cables....ATS eventually turns on the generator once the retic network says "piss off I'm rooted".

A broad input range VFD may be better suited for your application. (refer to my first sentence, there are limits)

Or, go wild and use a portable genset.

As someone suggest i should have step up the primary on my transformer. If all hell fails am getting me a portable genset

You'll find a new genset, complete with manufacturer's warranty, is the best way to go, Mildred.

Voltage drop/regulation, as others have pointed out, is the problem. The two main ways of improving them is unfortunately costly, mainly increasing the core size and/or the winding wire size.

Thicker winding wire on both primary and secondary reduces the voltage drop, as does making the laminations thinner, insulating them, and making sure they are tightly stacked with no gaps or burrs. Also check your connections at the tappings, they should be soldered if possible, then the leads connected with a nut, bolt, 2 washers and a split lockwasher under the nut.

As Tcmtech has already said, the taps would have been better on the primary rather than the secondary.

If the voltage drop under load is on the incoming feed then you are basically screwed as increasing the voltage taps will simply try to draw more current from a mains that is obviously already at its limit. Maybe you need to invest in a genset to overcome your problem

You may cheaply, temporarily add a properly rated or sized ( proper power handling capacity) VARIAC as the input source for your system when in the field where power line supply is way below the ratings of your present system..

A VARIAC (a trademark) is a continuously variable auto-transformer that resembles a big potentiometer. In the old days, this device were used as powerful light dimmers, before power semiconductors, thermistors were developed... Good luck and be safe!

This is an exact type of core that i use, someone had one and they overload it. so i made use of it

That certainly is a three phase transformer.

The open question here is it this transformer or the grid powering this transformer that is causing the limitation in your available power? I tend to believe that it is the grid and not the transformer because this transformer works well at some locations. The key thing you should test when your power is limited is what happens to the primary voltage when power is limited. If it proportionally sags the same amount as your secondary voltage then the grid and not your transformer is the problem. If the primary voltage remains constant then somewhere this transformer core is saturating.

Yes it was a three phase transformer that i got from a friend cause one of its phase was ruin. I use the core and turn it to a shell type transformer as u can see below in the next picture. Yes both side is affected when on load. the primary voltage is not constant.

I agree with Redfred based on the picture it is a three phase Transformer...

Depending on the ampere-turns, how the 3 separate (legs) windings, and the number of available taps for each of the three legs, the transformer can be operated as a single multi-tap auto-transformer, or an induction type. The available output voltages will be dependent on how the windings will be inter-connected. They can be configured as either series aiding, series opposing. Assuming the legs have balance windings, parallel connection will also be possible to increase its power capacity! An schematic diagram can make things easier to understand and follow!

Give us a drawing of what you did. Are you using a star and neutral 3 phase supply to drive it at the away locations or do you drive this from a single phase circiut?

OK, Romeo,

Having thought more about your problem, it seems to me your transfo ought to have much better regulation than you are getting. On a resistive load a transfo of this size would commonly have only 1% voltage drop from no-load to rated load (but maybe 4% on a pure inductive load). That would help your problem a lot.

The simple view, without any more information, is that you have windings which have too much resistance. Your lower photograph suggests you took the windings off the outer limbs of the transfo (but we can only see one in the picture). It is not clear if you kept all or part of original 240V winding or did a complete re-wind.

An original 3 phase transfo would have had to be 30 kVA rating to have a 240V winding with wire thick enough for 10 kVA/KW single phase rating.

Could you tell us please:-

1/ number of turns and wire size between each winding terminal, starting from live.

2/ Winding overall inner and outer diameters and length.

3/ Iron core cross section size X x Y. Also overall iron dimensions and "winding window" dimensions, if possible.

4/ Measured primary current and voltage, with no secondary load.

5/ measured primary and secondary currents & voltages at your rated load [8 kW].

If you do not have a shunt, then note that 5 metres of 4 square millimetre copper wire will drop 1 volt at about 45 amps at 20 Celsius copper temperature - I assume you have a Digital voltmeter with a 200 mV minimum AC range. If you turn on and measure within 10 seconds from cold, we can assume the copper is at room temperature. Laboratory accuracy is not needed.

For 115 V you would need 10 sq.mm copper, possible current about 80 amp.

I suggest you connect voltmeter to "shunt wire" after turning power on because inrush currents can be considerable & over-range meters.

Regards,

67model

If you are using 3 phase to drive a transformer, the supply must be in phase, most instalations the phases are mixed up as at most instalations when running a motor and it run in the wrong direction the quick way out is to just swap the phases at the Trip in the DB nothing to take appart. You need a phase meter to test the phase at your own instalation and make sure it is correct, if not fix your instalation wirring and then fix the Transformer input to still work as now. Going to a away place, use your meter to check their phasing, for your transformer to always perform at peak, phasing must be correct.

Rome0, now that you are aware of phasing, just a reminder that sound quality is also dependend on phasing and that every speaker in your system must be tested with a 1.5v D size battery, + to + and - to - and the speaker should move out. If all speakers are correctly wired, and you may be surprised to find how many are not then you only need to make sure that all feeds from the amp is in Phase, + to + and - to -.

rome0, a 10 000 Watt transformer need a 45A supply socket at 240V on Single phase and a 16Amp supply per phase on a 5 pin 3 Phase socket. For this type of Current supply at a single phase instalation you will have to wire directly into the mains supply in the DB or use the Isolator at the stove instalation.

Thanks alot guys for all your help. As many of you said. If the power is not there you cannot create it. if the power from the grid is low (190 volts) say if tested is 15 amp, its is impossible to pull 30 amps out of that main! I did some test on the transformer and found input current as low as 210 and 115 output i only get 7 volt drop when on load. Well i have invest on a 15 kv generator set and have already tested it and guess what. I don't have to worry on low power anymore. Thanks alot guys.

15 kVA not 15kv....

Thanks for the correction. Yes 15 kva...I was using my phone to reply to the discussion thats why i miss the "a" in kva.. my pc freeze everytime i use it to come on to the forum thread