Blew another damn transformer on my Trane XB80

Does not APPEAR to be another power source - - -

Reply to
clare
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I have to agree with Don. DC power component on secondary OR primary, or not connected right are the 2 most likely problems after "cheap crap component"

Reply to
clare

That would go a long ways to explaining his potty mouth.

Reply to
clare

If the back emf from the motor is causing the problem, the bad

** Not true at all.
** What is clear is that the primary has suddenly drawn a very large current and that means there are SHORTED turns inside the primary.

Go away wanker.

..... Phil

Reply to
Phil Allison

** You are both wrong.
** Which is no help to the OP.

.... Phil

Reply to
Phil Allison

Perhaps that goes all the way. Hey, I learned something about Oz today. Funny the guys from NZ I know seem quite nice. I suppose it was a surly lot they are descended from... or is it the climate? No matter.

Jeff

Reply to
Jeff Thies

Why would that be, in your words, "totally irrelevant" to whether or not the O.P. had any electrical/electronic failures elsewhere in his home attributable to voltage surges?

As opposed to 3 transformers blowing in the same appliance with nothing else anywhere in the home running into trouble from voltage surges?

While I have experienced roughly 8 transformers surviving repeated abusive pulse-in-reverse-direction developing about 2 KV across the primary without any degradation against ability to do so?

Why would the solution be deploying a capacitor, rather than repairing the poor connection or deploying a voltage-dependent spike-absorbing device such as an MOV?

So, why should we hear about problems about that from only one customer blowing 3 of them?

Why should 1 uF protect the trannies in question while 22-47 uF fails to protect a compact fluorescent lamp from a line voltage surge that blows even other electronics in 2 houses but did not blow any in-home trannies?

Certainly protects against applying for even a microsecond more than roughly 250-300 volts across transformer primaries, where it appears to me that we agree that transformer primaries usually survive 2,000 volts pulse voltage?

I seem to think that the trannies are probably blowing from either improper wiring (connecting only 1 of the 2 primary winding sections possibly noted for 120V usage), or from secondary load malfunction including bridge rectifier failure in manner of a diode "failing open".

Or, extreme-oddball trouble such as sticking a magnet to the tranny. But that's grasping-at-straws, like line voltage irregularities that blow

3 trannies in 1 piece of equipment but draw no other complaints such as blowing of electronics downstream of the tranny in question, or elsewhere in the house where one appliance blew 3 trannies.
Reply to
Don Klipstein

Please add helpfulness, as opposed to adding nothing but saying who is wrong.

I chimed in explaining stuff every time. At this point that I respond to, you are doing nothing but claiming who is wrong.

It appears to me, posting nothing but who is wrong is even lower than my grasping-at-straws bit of any magnets on the transformer in question.

Reply to
Don Klipstein

Yes, the thread got too long. If you saw the photo, and know the primary went open on 3 transformers, it sure looks like a problem on the primary side. If the load was too much, those wires on the secondary side would most likely have been at the very least discolored from the heat.

Tony

Reply to
Tony Miklos

Yes, many moons ago I was playing with adding a mylar cap in series with the primary of a neon sign transformer. It worked great for making the neon dimmer which was my attempt, but I recall measuring a much higher voltage across the cap due to the reactence and impedence of them in series. I'm guessing but I think it was up in the 400vac or so range maybe higher. Not good for the transformer winding either. I didn't blow them but stopped using them after reading the voltages.

Reply to
Tony Miklos

I am because I don't know why else it would have to be polarized.

Reply to
Tony Miklos

Yes, I looked at the pictures (rather poor resolution). The failure looks like a connection issue because there is no evidence of windings overheating. If the output was shorted the transformer would burn up - assuming it could sink enough current, but it would be unlikely to flare at one spot. This is a pretty standard 115VAC transformer, I've seen many of them...

If someone tried to pump 5000 volts into the transformer then possibly you could get an arc like that to the transformer frame, so that would mean a serious miss-wiring of the furnace where the igniter somehow was connected to the primary of the transformer and then turned on.

Hard to see that happening as the transformer powers the logic board that would enable the igniter to fire up!

John :-#)#

Reply to
John Robertson

A friend traveled to NZ then to OZ in 2004. He said when he got off the plane in NZ he thought the pilot had landed in China because 99% of the people around were Asian. I have relatives living near Sidney and they said this isn't the case there.

Reply to
Meat Plow

On 4/12/2011 8:10 AM Tony Miklos spake thus:

Well, it *is* a mystery ...

Reply to
David Nebenzahl

This makes me think the most likely causes are:

  • Improperly connecting the transformer (such as using only 1 of the 2 primaries of a 120/240V dual primary transformer)
  • DC flowing through the secondary. That can occur if the tranny's load has a fullwave rectifier with one diode open. If the fullwave rectifier has discrete diodes or a dual diode, the problem may be a bad solder joint at one of the diodes.

DC through the secondary is well known to be able to cause transformer cores to saturate. That can lead to the primary drawing excessive current.

  • Less likely - there is a magnet on the transformer core. That combined with the tranny's normal magnetic flux can cause core saturation, similar to the effect of DC in a winding although this usually only causes part of the core to saturate.

However, a magnet on the core appears to me "probably unlikely to be an actual problem" unless the tranny is of marginal design, line voltage is on the high side, or the magnet is especially powerful.

There is the matter of voltage spikes on the primary blowing the insulation. However, I consider that unlikely if nothing else has been blown while 3 transformers blew.

Reply to
Don Klipstein

That's not true. an open rectifier does not allow DC current to flow through the secondary. It's just 1/2 of the power line cycle. During the opposite half of the cycle, no current flows in the secondary. True, it's unidirectional current, but it's an intermittent current, not constant DC. If your statement were true, then half-wave rectifiers wouldn't be feasible.

Reply to
Dave M

"Dave M"

** So the average value is non zero and that means there is a DC component to the current.
** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the primary current.

.... Phil

Reply to
Phil Allison

A unidirectional pulsing waveform has a DC component.

That analyzes to a sum of DC, fundamental frequency AC, and AC at harmonic frequencies. The average as averaged over a whole cycle is the DC component.

It is fairly well known that a transformer driving a halfwave rectified load can run into core saturation problems from the DC component in the unidirectionally pulsing current waveform.

Reply to
Don Klipstein

In addition to all the other observations and suggestions found in this thread, there is one additional possibility to consider: Your Trane machine simply hates you.

I've seen malevolent machines. I've been victimized by our metal overlords.

Tell the truth, have you never been tempted to shotgun a lawnmower?

Reply to
HeyBub

And the FACT that the furnace in question uses a hot plate ignitor further removes that scenario from any semplance of possibility

Reply to
clare

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