Autoformer issue

[rfaulkner99]

Can someone with a Hughes Autoformer
tell me if it is normal to measure around 10 ohms of resistance between the hot and neutral prongs of the plug? I was expecting infinite resistance, so hoping to see if this is normal or not.

Initially I thought it was the plug, because there was some corrosion and melting on on the hot terminal, but I cut off the plug and the bare wire measures the same.

Thanks

[MEXICOWANDERER]

You'll get a better response asking a battery company about their plates.

[time2roll]

I don't know any company that is going to supply a schematic except to an authorized repair facility.

[wa8yxm]

Cummins12V98 wrote:
If you want a FACTUAL answer simply contact AutoFormer!

THeir response was already up -thread

For the person who ask. I'm not good at drawing with the computer and do not have the kind of tablet that would let me draw it.

So I will describe

I needed to, as I recall buck about 10 volts
So it was a 10 volt transformer.. Primary connected to incoming power. I "Broke" one lead of the device's power transformer (A tube tester by the way) and put the secondary (10 volt) winding of the buck transformer in such a way that it was out of phase so it "Bucked" the incoming power.. Worked great Was able to dial the needel to the calibration mark every time.

Simple really.

[MEXICOWANDERER]

Hughs belongs on Saturday morning TV along with Ron Popiel, adjustable reading glasses and miracle wrinkle cream AFAIK.

They did not answer 3 separate USPS letters. I asked how many db isolation their product provided. The first letter prompted a mere BUY NOW offer the 2nd and 3rd were ignored. Voltage limit cutouts and misconnection cutouts are very useful but the gizmo is indeed a multi tap autoformer. I dissected one about 15 years ago that caught fire. My Sola + - 40% frequency regulated system has a 30 amp capacity with a FULL isolation transformer secondary. Bad part it eats 133 watts sitting on it's butt. But Hugh's is on my **** list for dishonesty.

I build whole house voltage de-spikers with gas tube lightning diverters, 10 20- mm MOVs and multiple TVS suppressors EACH DEVICE having it's own BUSSMAN micro fuse. The system is not cheap to build

[Cummins12V98]

If you want a FACTUAL answer simply contact AutoFormer!

[RCMAN46]

wa8yxm wrote:
I have wired a buck (As I recall) transformer not an auto-transformer (Though I have small ones for device testing)

The transformer had two windings ONe wired "In phase" with the primary transformer in the device and the other (The buck coil) out of phase .

Hughs is saying that is how they are doing it.. I won't argue. There is a very good reason to do it this way But without opening it up and taking measurements I can't be sure what they did. Thus I will take their word for it for now since they make the thign.

IF you have an internal schematic I can look at then I can tell you for sure.
But I'm not opening the case.

I will settle for a wiring schematic of your two winding transformer that is not an auto-transformer.

[Lynnmor]

I think that the old code only pertained to the campground so that autotranstormers wouldn't be used in the supply side, that is my interpretation. The new code may be going after the customers for various reasons. Try reading the old and new to see what I am guessing at.

[wa8yxm]

I have wired a buck (As I recall) transformer not an auto-transformer (Though I have small ones for device testing)

The transformer had two windings ONe wired "In phase" with the primary transformer in the device and the other (The buck coil) out of phase .

Hughs is saying that is how they are doing it.. I won't argue. There is a very good reason to do it this way But without opening it up and taking measurements I can't be sure what they did. Thus I will take their word for it for now since they make the thign.

IF you have an internal schematic I can look at then I can tell you for sure.
But I'm not opening the case.

[DrewE]

wa8yxm wrote:

I am not sure if the Autoformer is an Autotransformer or a tapped transformer.

Hughes actually claims it's not an autotransformer, in as much as it has separate line and load windings. In my opinion, and from what all I can suss out about how they're constructed, Hughes is being misleading in making that claim: while the transformer itself presumably does have separate windings for the input and output, the two sets of windings are connected together when it's in use and so wired in an autotransformer configuration. (Buck/boost transformers are pretty standard components used in e.g. some industrial installations, and there's nothing to suggest that the Hughes device is anything much different than one of them along with some associated switching circuitry.)

I think their response to the recent NEC changes that prohibit autotransformers for RV park use is also rather telling. They have come out quite vocally against these changes, saying basically that they are pointless and senseless and were promoted by parties with less than pure motives, and then continue on with "but they don't apply to our products anyhow." While the first bit may well be true, and I tend to agree that it's a rather bizarre restriction as stated, why would they be so vocally against it if they were certain their product was not affected by the new code?

(As an aside, the NEC has long had a prohibition on the use of autotransformers in RV converters which at a casual glance might seem to apply a little more broadly. That's unrelated to autoformer/voltage booster use.)

[wa8yxm]

time2roll wrote:
Autoformer is not an isolation transformer but rather one big coil with several tap points to get the different voltages. How would it work with an open circuit? There is no power switch.

If this is about the plug melting, this is fairly common during high usage as many pedestal connectors are worn, pitted, dirty and corroded causing a poor connection and some heat.

I am not sure if the Autoformer is an Autotransformer or a tapped transformer.

[CA_Traveler]

Water on the ground increases the likelyhood of feeling a shock with faulty equipment. The shock potential may have existed prior to the rain.

[rfaulkner99]

Let me add one more detail to the mix. Before I discovered the shock issue, my EMS shut off the power while the Autoformer was connected due to an open ground (according to the error code). I checked the Autoformer and it was extremely hot to the touch - I attributed this partly to the fact that it was the hottest part of the day with temps in the upper 90s and the fact that I had placed a small trash can over the Autoformer to protect from rain, and it had very little if any ventilation. After I removed the Autoformer, the open ground condition went away.

A few hours later after I had let the Autoformer cool down, I plugged it back in and just positioned it under the RV to protect from rain with better ventilation. It seemed OK until the shock incident.

[CA_Traveler]

A shock from the frame is a resut of 2 probems:
1. You have a ground fault (leak to the frame-ground.
2. You have a open (or high resistance) ground to earth ground connection.

The autoformer could have both. Open the autoformer and check all connections which should be clean and tight.

RV plugs and RV pedestals are notorious for poor maintenance, you've already identified at least one bad plug.

[RCMAN46]

The Hughes Autoformer I have has triacs that determine which transformer tap is active. As such measuring dc resistance between hot input and the hot output may be something much higher than expected as you are going through a triac.

There will be some resistance between the neutral and hot due to the voltage sensing circuit in the Autoformer.

The neutral lead goes direct from the input to the output so it should measure very low in dc resistance.

When I first received my Autoformer Hughes had reversed the output leads which resulted in the hot lead being on the neutral of the output. Also my trailer was wired wrong in that the ground and neutral had been bonded. This resulted in the trailer frame connected to the hot lead. Thus you will receive a shock if you touch the trailer while standing on the ground outside the trailer.

This can be checked on the Autoformer. As stated above the neutral goes direct through the Autoformer. Thus input neutral to output neutral should be a very low dc resistance. The hot goes through the transformer and because of the triacs there will be some resistance measured between input and output hot leads.

There should be infinate resistance between ground on the Autoformer and either the hot or neutral lead.

I discovered my problem when my Hughes was new and Hughes replaced my Autoformer under warranty.