Author Topic: Forklift battery charger X-former peculiarities  (Read 848 times)

Offline rikkitikkitavi

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Forklift battery charger X-former peculiarities
« on: October 07, 2020, 05:09:34 PM »
I have quite a large xformer pulled from  a forklift battery charger

It consists of an ordinary toroid of about 10+ kgs , and an inductor in series with primary.

What is so peculiar is that applying 230VAC ( it s probably old enough to be rated 220V) it goes into partial saturation, idle current is about 0,4 Amps.
Voltage across inductor is about 15VAC.

I presume it is designed this way to enable the charging of a fully empty battery, which pulls a lot of current, causing quite a voltage drop across the inductor impedance and hence limits current until battery has absorbed enough charge to raise the voltage and charging current decreases?

The charger only contained a thermal switch breaking primary voltage and a couple of beefy electrodes. And some on-lights and an amp meter of course.

Sadly this means that the transformer is useless as connecting it directly to 230VAC will probably saturate it fully or very closely so idle current is in the amps range. It hums and burrs...

I could always add primary turns to it outside the secondary but it is a bit of hassle.

Any other proposals apart from the obvious to use the inductor in series as designed?
A man can not have too many variacs

Online davekni

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Re: Forklift battery charger X-former peculiarities
« Reply #1 on: October 07, 2020, 06:19:32 PM »
Take it to Japan or other place where 200V is common, or to a 60Hz country like here (USA) where it might work at 240V :)
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Offline rikkitikkitavi

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Re: Forklift battery charger X-former peculiarities
« Reply #2 on: October 07, 2020, 06:31:07 PM »
Lol.

Yes 60/50*215 = 258V . Thats even with some margin for voltage surges.

You have 2 phase 240V right (180 degrees out of phase) ? With centertap to gnd?
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Re: Forklift battery charger X-former peculiarities
« Reply #3 on: October 07, 2020, 08:29:26 PM »
Yes.  We typically just call it single-phase, as 180 degrees isn't useful for much.  Most outlets are just 120V, one side or the other of the center-tapped 240V that comes into the breaker panel.  Large power appliances such as the clothes dryer use 240V.  That's the outlet I use for my DRSSTC, 240V at 40A.  3-phase would be wonderful, but is used primarily for commercial buildings here.
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Offline klugesmith

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Re: Forklift battery charger X-former peculiarities
« Reply #4 on: October 07, 2020, 09:40:47 PM »
Split phase comes with a risk of damage when neutral conductor is broken (as from bad weather).  Then the 120 volt branch circuits can divide the 240 volts arbitrarily, depending on what loads are turned on.

The corresponding 3-phase (like in building where I worked before Covid) is 120 V phase to neutral, 208 volts phase to phase.
About 10 years ago the new-ish wiring to some office cubicles developed an open neutral, and in a 5 minute period several PC power supplies lost their smoke. (PS with universal input voltage, not selected by switch, cost more.)

Curiously, the next step up isn't a factor of 2, it's 277 phase to neutral which is 480 phase to phase.
My low pressure sodium vapor luminaires, retired from parking lot service, have ballasts tapped only for 208 and 277.
Presumably at the direction of their maker's marketing department.
« Last Edit: October 07, 2020, 09:55:21 PM by klugesmith »

Offline rikkitikkitavi

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Re: Forklift battery charger X-former peculiarities
« Reply #5 on: October 07, 2020, 10:41:57 PM »
We have three phase here, 400V phase-phase and hence 230V to ground, and most houses have it , but most appliances and media equipment etc is 230V and that is what you find in a typical socket outlet. Some large consumers like water heater, heat pumps, electrical heaters have 400V, and in any decent home workshop you have a 400V outlet socket or two, typically 16A fusing.

I know of a few cases where the substation lost the neutral connection and hece the 230V was all over the place. Usually quite expensive for the electrical company as you might take out a block or two of everything electrical, depends how well they managed to divide loads equal on the three phases.
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Offline rikkitikkitavi

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Re: Forklift battery charger X-former peculiarities
« Reply #6 on: October 08, 2020, 09:37:17 AM »
I think I solved it now after a good nights sleep... (did some crossfit outdoor last evening so it was very good sleep, not so good muscle ache today...)

I have a small EI core with a splitt bobin , at aboutish 80VA or so. I will wind it with a 20Vish primary and a secondary with the same turns ratio roughly.

Both primary and secondary will be series connected. This second transformer then replaced the inductor and I have an ordinary "stiff" transformer with low internal impendance.
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Offline rikkitikkitavi

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Re: Forklift battery charger X-former peculiarities
« Reply #7 on: October 08, 2020, 09:43:20 AM »
Another peculiar xformer.. Or not perhaps.

Just two primaries (grey /blue) but with a lot of possible connections. Took a while to sort them out.

How do you spend your evenings? :)

The insulation is cotton gauze resin bonded. Is this another anchor for my little boat or can it be removed?
100C water  doesn't soften it.

But there is little of the secondaries that is useful
 
I wonder if I ever need a 2500VA toroid apart from the others I have...

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Offline rikkitikkitavi

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Re: Forklift battery charger X-former peculiarities
« Reply #8 on: October 08, 2020, 03:03:36 PM »
I did measure the inductor aswell. See attached picture. It is not small...
It has two windings , that was in series. Now I cut them open. They are each atleast 80-90 turns.

I cant lift the transformer itself in one hand and take a photo with the other regardless of present muscle ache, it is like a medium/small size kettlebell in weight, and ergo, if nothing else I got new use for my Xformers because good kettlebells are quite expensive:)
I could even short the turns, add some extra weight in the shape of induction coils on my legs with a battery pack on the back and increase the load not just by gravity but with electromagnetism, haha.

Current increases with about 3Volts applied on one of the windings, or atleast the current increases AFAIK on the analog meters on my variac. I can not adjust voltage finely enough with my variac. I probably needs to add another step down transformer  to accurately measure current and voltage relation.
Current was about 0,2Amps then, equating about 15 ohms impendance or 50mH inductance (we are at 50Hz here) if I do my math right.

If the toroid has a hidded air gap in the core under all the windings and tape the relation voltage/current should be fairly linear I presume.

Otherwise it is an ordinary transformer that goes into saturation very early for no apparent reason as 90 turns X 2 on a core this size should withstand  higher induced flux (is this the correct term in english? ie volt*seconds) , berhaps a shorted turn somewhere.

Edit: just realised what I can use a transformer that has no use as a transformer as :)
« Last Edit: October 08, 2020, 03:31:45 PM by rikkitikkitavi »
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Offline klugesmith

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Re: Forklift battery charger X-former peculiarities
« Reply #9 on: October 08, 2020, 05:06:39 PM »
Couple posts up, you mentioned putting windings on an 80VA size core.  I think to create a 210:20 transformer, for a low impedance replacement of your voltage_dropping/current_limiting inductor.

That would be called a buck transformer;  the word is often seen as part of "buck boost transformer".
Not to be confused with switch mode buck and boost converters.
Industrial catalogs list buck boost transformers for prices higher than conventional transformers that could be applied the same way.  For safety reasons not immediately obvious to everyone, NEC says "An over-current device shall not be installed in series with the shunt winding between points A and B" in diagram 450-4 (look it up).

Looking for a picture, I found this video with low information content. Except it taught me about boosting (or bucking) three phase delta power using two autotransformers.

/>
Glad to hear you are working out.  Was reminded of why free weights with a short bar in the middle are called dumbbells.  Dumb as in no voice.  Bell as for making noise.  Hundreds of years ago, bell ringers developed strong arms.  Learned to do the developing quietly, using bells without clappers.
« Last Edit: October 08, 2020, 06:03:54 PM by klugesmith »

Offline rikkitikkitavi

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Re: Forklift battery charger X-former peculiarities
« Reply #10 on: October 08, 2020, 08:24:19 PM »
Hmm, not quite what I had thought of but learning the mysteries of X former circuits is always fun

https://sound-au.com/articles/buck-xfmr.htm
(I often turn to Rod Elliot for advice)

My idea was more to use two transformers in series so to speak, because the secondary could be boosted a bit more too. I wanted about 30VAC.
So one 215/26+ one 25/4 V

Dumbells , yes that is a name I heard for free weights, we say "hantel" in Swedish. But "Kettlebell" aswell. And burpees. Lots of burpees.
"Is a single burpees called a burpii? No, you never just do one"..
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Offline rikkitikkitavi

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Re: Forklift battery charger X-former peculiarities
« Reply #11 on: October 09, 2020, 11:03:32 AM »
Did some measurements on the toroidal inductor, but only with a single winding,it has two in series. Measured current and voltage across a single winding @ 50Hz.
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Re: Forklift battery charger X-former peculiarities
« Reply #11 on: October 09, 2020, 11:03:32 AM »

 


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