Honda EU2000 Transformer Problem

[bcroe]

don't get too fancy, the heater elements are going to fail from the thermal
shock pretty quickly. I think the big light bulb as ballast, will be the better load.

Water heater elements are the resistors of choice here for very short term high power. The
problem with light bulbs, the resistance starts very low, and then increases, just the opposite
of what you need. A 144 ohm 100W bulb starts at 10 ohms cold.

I wonder if you are using an auto transformer? This would have half the iron, etc of a
straight 2:1 transformer of same rating. Also wondering, if a tape wound core would
perform any better; certainly has less losses? Use a 240 V Vari*c with center tap.

Bruce Roe

[Sunking]

Water heater elements are the resistors of choice here for very short term high power. The
problem with light bulbs, the resistance starts very low, and then increases, just the opposite
of what you need. A 144 ohm 100W bulb starts at 10 ohms cold.

Precisely. It has to be a negative coefficient to work correctly.

Hey Chris just for giggles can you try a variety of bulbs of different wattage's? Say start with 10 watts and work your way up. Mike has a point a light might work. It could be you just were not in the right range.

I also agree with Bruce this should have been a non issue if a straight dry type single phase transformer were used. Auto Transformer is really the wrong hardware to use. Not only that but a lot less expensive using a 2 Kva Single phase Transformer in reverse, making it a step up transformer.

[ChrisOlson]

Firstly, yes the transformer is an autotransformer - it is an Outback PSX-240. The reason that the autotransformer is the best choice here is because we have it wired up like our system is here - it is used for leg balancing his 4.0 kVA Perkins diesel generator as well as producing the 180 degree out of phase sine wave for the single phase generator. So it is dual-purpose.

The biggest light bulbs we got around here are a couple 75 watt heat lamps. I tried one of those and it didn't work. Otherwise the next biggest bulbs we got are maybe some 25W CFL's. Out here in the sticks we just have no use for big wattage lights so I'd have to run to town to find something like that.

I just happened to have the water heater elements in my shop because I keep a few spares on hand. I use them for resistors in my wind turbine voltage clippers as well as electric water heating. They're only $8.99 each and they're actually pretty tough. I got an array of three of them wired delta in a wind turbine voltage clipper box here that has been in service for over two years. That box is on an outside panel on a steel post because it's a fire hazard. I got those three water heater elements on aluminum heat sinks in the box and sometimes when the wind blows hard and the turbine tries to over-volt the Classic so the clipper comes on constant to "clip" the voltage below 150V, that box gets so hot you can't touch it, and if you spray water on the box you get instant steam. That's hot and ever burned one out yet.

This soft start box I built today doesn't get anywhere close to that hot because it's only for a brief second or so it's needed to "soften" the blow from the transformer. So I think it'll work fine. I'm just building a little safety into it in the event somebody starts the generator and forgets to throw the switch - and the heater element should be able to burn up or handle it long enough to overload fault the generator without causing a fire. The element is no big deal - if it fails it's only $8.99 to replace it.

[inetdog]

Just got back from the neighbor's place. One water heater element worked. But it make the generator grunt and the overload light flashed on for a brief instant before I flipped the switch. The transformer load is only about 10 watts once the core gets magnetized but the heater load is 2,000 watts which is all the little generator can put out on surge initially.

The heater load will only be 2,000 watts if you put it in parallel with the transformer OR the impedance of the transformer core is so low that it looks like a short circuit in series with the heater.
Only if the inverter has an enormous VA capacity compared to its wattage capacity would that even potentially give a higher load on the generator with the switch open than with the switch closed. Something still does not seem right.

If you are saying that the inrush to the transformer still is on the brink of overloading the inverter, put two of the heater elements in series instead of one.

[ChrisOlson]

The heater load will only be 2,000 watts if you put it in parallel with the transformer OR the impedance of the transformer core is so low that it looks like a short circuit in series with the heater.

Once the core is magnetized, and with no load on the transformer secondary, the impedance of the transformer is very, very low. I tried to measure the resistance of a winding once when I had a problem with the breaker on mine and you can't measure it without a DLRO.

[bcroe]

Once the core is magnetized, and with no load on the transformer secondary, the impedance of the transformer is very, very low. I tried to measure the resistance of a winding once when I had a problem with the breaker on mine and you can't measure it without a DLRO.

The resistance is supposed to be as low as practical, for efficiency. The AC impedance at 60 HZ
can't be measured by a simple (DC) ohm meter. it appears your auto transformer is much larger
than the small generator requires, helping to create the problem. Bruce Roe

[ChrisOlson]

The resistance is supposed to be as low as practical, for efficiency. The AC impedance at 60 HZ
can't be measured by a simple (DC) ohm meter. it appears your auto transformer is much larger
than the small generator requires, helping to create the problem. Bruce Roe

When I tried to measure mine the one time the ohm meter just shows zero. It can't measure the resistance of the winding. I figured maybe a DLRO could though. I ain't no electificution engineer but I think you need a meter than can measure capacitance in order to calculate the AC impedance for various frequencies.

Unfortunately, the transformer is way too big for the little generator. The transformer can handle a 6.0 kVA imbalance. It's got a huge core and the thing weighs like 60 lbs. I'm not sure what size the windings are but they're at least 10 AWG windings in it. They bought that transformer because it's the same thing we got and it works good and never even gets warm to the touch. It's a pretty commonly available transformer that's known to be tougher than nails and you can't wreck it.

[Sunking]

Once the core is magnetized, and with no load on the transformer secondary, the impedance of the transformer is very, very low. I tried to measure the resistance of a winding once when I had a problem with the breaker on mine and you can't measure it without a DLRO.

You cannot measure impedance with a DRLO or any ohm meter. All a DRLO can do is verify no windings have shorted out assuming you knew what a good reading was before hand.

[Sunking]

When I tried to measure mine the one time the ohm meter just shows zero. It can't measure the resistance of the winding. I figured maybe a DLRO could though. I ain't no electificution engineer but I think you need a meter than can measure capacitance in order to calculate the AC impedance for various frequencies.

Unfortunately, the transformer is way too big for the little generator. The transformer can handle a 6.0 kVA imbalance. It's got a huge core and the thing weighs like 60 lbs. I'm not sure what size the windings are but they're at least 10 AWG windings in it. They bought that transformer because it's the same thing we got and it works good and never even gets warm to the touch. It's a pretty commonly available transformer that's known to be tougher than nails and you can't wreck it.

Well I drive electric trains, so that makes me an electric enjunire.

Seriously though you do not have the test equipment to determine the impedance. In all seriousness impedance does not matter. The actual impedance is determined by the turns ratio of the transformer and the load impedance. Perhaps you recal the ole days of Audio when tubes were used. Most of the gear had connections for 2, 4, 8, 16, and 32 ohm speakers. All it was is a transformer with multiple taps on the secondary to match speaker impedance to the tube amp impedance which was relatively high. For example if the tube amp impedances was 512 ohms, the transformer turn ratio was 1 to 256, 128, 64, 32, and 16 respectively. The core permeability has to be reactive for the frequency of interest to work.

[ChrisOlson]

Well I drive electric trains, so that makes me an electric enjunire.

Well, I for sure ain't no electric injuneer. But I took my fancy box over to the neighbor's after lunch and wired it all up and it works. We set the inverter on 6 amps Gen Support level and tried it with a 3,500 watt load on the inverter and it worked good - the SCP showed the generator putting out 1.404 kVA. And the power must be pretty clean because the XW sync'd with it and qualified it within 30 seconds.

Not sure if the PSX-240 transformer has separate primary and secondary or it is one big winding with a center tap. It has four leads coming out of the transformer winding so I think it has separate primary and secondary windings in it.

[Sunking]

Not sure if the PSX-240 transformer has separate primary and secondary or it is one big winding with a center tap. It has four leads coming out of the transformer winding so I think it has separate primary and secondary windings in it.

Don't get your shorts in a knot Chris, I was not trying to offend you.

That is what Bruce and I were trying to tell you that an Auto Transformer is not a good choice for the application. It will work but with sacrifices like very high core saturation currents that make CB's go pop like is happening to you. An auto transformer is just as you describe a single winding. A transformer has an isolated primary and at least one secondary winding. Had you used that this would not be an issue is all we are saying. Not only would it have worked, it would have been less expensive. You can get a 2 Kva transformer for peanuts, about 200 peanuts.

[ChrisOlson]

Yeah, the only thing is that he wanted to be able to use the transformer to leg balance his Perkins diesel generator too. Without the transformer he has to set a conservative gen support level on the Perkins or it will trip the breaker on it and he can't use it for battery charging.

So the transformer is doing two things - leg balancing one generator and producing L2 for the other one - and I don't know if you could do that with a regular transformer.

I know the core saturation on the autotransformer is really big. Our power room is on the other side of the north kitchen wall and our autotransformer is hanging on that wall. When our big Honda generator auto-starts we know when it starts because that transformer makes a horrible "thud" that rattles the cups in the cupboard

[inetdog]

Yeah, the only thing is that he wanted to be able to use the transformer to leg balance his Perkins diesel generator too. Without the transformer he has to set a conservative gen support level on the Perkins or it will trip the breaker on it and he can't use it for battery charging.

So the transformer is doing two things - leg balancing one generator and producing L2 for the other one - and I don't know if you could do that with a regular transformer.

I know the core saturation on the autotransformer is really big. Our power room is on the other side of the north kitchen wall and our autotransformer is hanging on that wall. When our big Honda generator auto-starts we know when it starts because that transformer makes a horrible "thud" that rattles the cups in the cupboard

You can do anything with an isolation transformer that you can with an autotransformer, just be wiring it up the right way.
What the autotransformer theoretically provides is a little less copper usage and a smaller overall package since you do not need to separate the windings.
When you go to a 1:1 ratio of primary to secondary (or partial winding to full winding) many of the advantages of an autotransformer go away.

[ChrisOlson]

OK, well, being I got a bunch of electrificution engineers right handy here, and these electrificution engineers are willing to teach me, I need to learn these things......

So an autotransformer is just a big electrical steel core with a big coil of copper around it that's center tapped? Here's a photo of the inside of our transformer - this is the same unit the neighbor just got:



We had a problem with the breaker on ours once and I was checking it out with the ohm meter because I thought it had a burnt out winding. It has four wires coming out of it - a red and a black and two whites. IIRC I had no continuity between the red and black. But I had continuity from the red to one white and from the black to the other white. If I hooked the whites together (where they normally are on the neutral bus in the thing) then I had continuity from the red to the black.

So how come there's four wires coming out of the confounded thing?

[bcroe]

OK, well, being I got a bunch of electrificution engineers right handy here, and these electrificution engineers are willing to teach me, I need to learn these things......

So an autotransformer is just a big electrical steel core with a big coil of copper around it that's center tapped? Here's a photo of the inside of our transformer - this is the same unit the neighbor just got:



We had a problem with the breaker on ours once and I was checking it out with the ohm meter because I thought it had a burnt out winding. It has four wires coming out of it - a red and a black and two whites. IIRC I had no continuity between the red and black. But I had continuity from the red to one white and from the black to the other white. If I hooked the whites together (where they normally are on the neutral bus in the thing) then I had continuity from the red to the black.

So how come there's four wires coming out of the confounded thing?

What you have is a 2 winding 120 VAC to 120 VAC transformer, used to create an out of phase power
leg. It only needs to be large enough to carry 120 V loads on the added leg, perhaps 1000 VA (half).
If a 240 V load were placed across both legs, the same could support 2000 VA (working as an auto
trans). Bruce Roe