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Identifying buck-boost transformer windings?

Started by DaveC February 11, 2014
Imagine you are asked to install a used buck-boost transformer. Imagine you 
could normally do this in a few minutes. Except if the leads were cut short 
such that identifying characters on the leads' insulation were missing. 

Identifying 2 leads belonging to any one winding is straightforward ohm meter 
work. Maybe use of a ESR meter might help separate the X windings from the H 
windings?. But identifying which specific winding is which and which end is 
which��not so straightforward. For me. 

How would you go about identifying the windings? Maybe use a Variac to input 
voltage to each of the windings then measure the output of the others? What 
outputs should I expect at, for example, the H3/H4 winding with a voltage on  
H1/H2 winding? How to identify backward connection of a winding? 

Are the two H windings identical? The two X windings? 

Suggestions welcome. 

This is a 208 -> 230 (ie, 12 & 24 v buck-boost voltage) single-phase 
autotransformer in N. America. 

Thanks.

The tech support people at a couple of transformer manufacturers couldn't 
help.

Dave

"DaveC"  wrote in message 
news:0001HW.CF1FBCBB056C00BCB01029BF@news.eternal-september.org...

> How would you go about identifying the windings? Maybe use > a Variac to input voltage to each of the windings then measure > the output of the others?
Why not try it and see? Then we'll be able to study the data and give you some advice.
On a sunny day (Tue, 11 Feb 2014 12:19:15 -0800) it happened "William
Sommerwerck" <grizzledgeezer@comcast.net> wrote in
<lde0k6$l3d$1@dont-email.me>:

>"DaveC" wrote in message >news:0001HW.CF1FBCBB056C00BCB01029BF@news.eternal-september.org... > >> How would you go about identifying the windings? Maybe use >> a Variac to input voltage to each of the windings then measure >> the output of the others? > >Why not try it and see? Then we'll be able to study the data and give you some >advice.
I have put transformers on the soundcard output with sgen signal generator (Linux). If you have a decent audio power amp you can even run stuff from it. I did run my cryocooler at 60.5 Hz (specified) that way from the soundcard with a 230 to 40V transfomer in reverse, 100W or so. Volume control!! A real potmeter on the amp! Should have taken a picture... Now it is back on original transistor PWM unit.
On Tue, 11 Feb 2014 11:40:43 -0800, DaveC <invalid@invalid.net> wrote:

>Imagine you are asked to install a used buck-boost transformer. Imagine you >could normally do this in a few minutes. Except if the leads were cut short >such that identifying characters on the leads' insulation were missing. > >Identifying 2 leads belonging to any one winding is straightforward ohm meter >work. Maybe use of a ESR meter might help separate the X windings from the H >windings?. But identifying which specific winding is which and which end is >which&#2013266093;&#2013266093;not so straightforward. For me. > >How would you go about identifying the windings? Maybe use a Variac to input >voltage to each of the windings then measure the output of the others? What >outputs should I expect at, for example, the H3/H4 winding with a voltage on >H1/H2 winding? How to identify backward connection of a winding? > >Are the two H windings identical? The two X windings? > >Suggestions welcome. > >This is a 208 -> 230 (ie, 12 & 24 v buck-boost voltage) single-phase >autotransformer in N. America. > >Thanks.
I have the wiring diagrams in .pdf for Square D buck/boost xmfrs. The X wires are the heavy wires and the H wires the thin wires. X1 and X2 are the ends of one winding. X2 and X3 the ends of another winding. The other windings are similar. Anyway, if you send me an email I'll send you the .pdf of the wiring manual. Then you will be able to figure out how to wire the thing. It should be easy enough, just measure the output in one random configuration and you will be able to tell what's what by looking at the manual. Eric --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com
DaveC wrote:
> Imagine you are asked to install a used buck-boost transformer. Imagine you > could normally do this in a few minutes. Except if the leads were cut short > such that identifying characters on the leads' insulation were missing. > > Identifying 2 leads belonging to any one winding is straightforward ohm meter > work. Maybe use of a ESR meter might help separate the X windings from the H > windings?. But identifying which specific winding is which and which end is > which&#2013266093;&#2013266093;not so straightforward. For me. > > How would you go about identifying the windings? Maybe use a Variac to input > voltage to each of the windings then measure the output of the others? What > outputs should I expect at, for example, the H3/H4 winding with a voltage on > H1/H2 winding? How to identify backward connection of a winding? > > Are the two H windings identical? The two X windings? > > Suggestions welcome. > > This is a 208 -> 230 (ie, 12 & 24 v buck-boost voltage) single-phase > autotransformer in N. America. > > Thanks. >
Assuming you have ohmed them all out and thus know how many windings there are and how many taps each has: Hook a function generator to one winding (any winding), best one that has no taps. Measure the amplitude you get at a 10kHz or so. Most multimeters will do that, or a scope. Now measure the amplitude at all others. That gives you roughly the turns ratios. Now you normally also need to know which one is the helper winding because that sits close to the primary in the stack and should under no circumstance be mixed up with any of the scondaries. From your previous measurement you know which one is the primary (on 120VAC to low DC supplies that's the one with the highest number of turns). Hook that to one side of the capacitance terminal on your multimeter. Keep leads as short as possible. Measure capacitance to all others. Usually the highest capacitance indicates which windings are closest to each other. -- Regards, Joerg http://www.analogconsultants.com/
Joerg wrote:
> DaveC wrote: >> Imagine you are asked to install a used buck-boost transformer. Imagine you >> could normally do this in a few minutes. Except if the leads were cut short >> such that identifying characters on the leads' insulation were missing. >> >> Identifying 2 leads belonging to any one winding is straightforward ohm meter >> work. Maybe use of a ESR meter might help separate the X windings from the H >> windings?. But identifying which specific winding is which and which end is >> which&#2013266093;&#2013266093;not so straightforward. For me. >> >> How would you go about identifying the windings? Maybe use a Variac to input >> voltage to each of the windings then measure the output of the others? What >> outputs should I expect at, for example, the H3/H4 winding with a voltage on >> H1/H2 winding? How to identify backward connection of a winding? >> >> Are the two H windings identical? The two X windings? >> >> Suggestions welcome. >> >> This is a 208 -> 230 (ie, 12 & 24 v buck-boost voltage) single-phase >> autotransformer in N. America. >> >> Thanks. >> > > Assuming you have ohmed them all out and thus know how many windings > there are and how many taps each has: > > Hook a function generator to one winding (any winding), best one that > has no taps. Measure the amplitude you get at a 10kHz or so. Most > multimeters will do that, or a scope. Now measure the amplitude at all > others. That gives you roughly the turns ratios. > > Now you normally also need to know which one is the helper winding > because that sits close to the primary in the stack and should under no > circumstance be mixed up with any of the scondaries. From your previous > measurement you know which one is the primary (on 120VAC to low DC > supplies that's the one with the highest number of turns). Hook that to > one side of the capacitance terminal on your multimeter. Keep leads as > short as possible. Measure capacitance to all others. Usually the > highest capacitance indicates which windings are closest to each other. >
Oops, if yours is not an "electronic transformer" disregard the above. But then it's not really buck/boost. -- Regards, Joerg http://www.analogconsultants.com/
On 2/11/2014 1:40 PM, DaveC wrote:
> Imagine you are asked to install a used buck-boost transformer. Imagine you > could normally do this in a few minutes. Except if the leads were cut short > such that identifying characters on the leads' insulation were missing. > > Identifying 2 leads belonging to any one winding is straightforward ohm meter > work. Maybe use of a ESR meter might help separate the X windings from the H > windings?. But identifying which specific winding is which and which end is > which&#2013266093;&#2013266093;not so straightforward. For me. > > How would you go about identifying the windings? Maybe use a Variac to input > voltage to each of the windings then measure the output of the others? What > outputs should I expect at, for example, the H3/H4 winding with a voltage on > H1/H2 winding? How to identify backward connection of a winding? > > Are the two H windings identical? The two X windings? > > Suggestions welcome. > > This is a 208 -> 230 (ie, 12 & 24 v buck-boost voltage) single-phase > autotransformer in N. America. > > Thanks. >
Hey dave.. Imagine only sending this to groups that would be interested. Woodworking , probably not
On Tue, 11 Feb 2014 11:40:43 -0800, DaveC <invalid@invalid.net> wrote:

>Imagine you are asked to install a used buck-boost transformer. Imagine you >could normally do this in a few minutes. Except if the leads were cut short >such that identifying characters on the leads' insulation were missing. > >Identifying 2 leads belonging to any one winding is straightforward ohm meter >work. Maybe use of a ESR meter might help separate the X windings from the H >windings?. But identifying which specific winding is which and which end is >which&#2013266093;&#2013266093;not so straightforward. For me. > >How would you go about identifying the windings? Maybe use a Variac to input >voltage to each of the windings then measure the output of the others? What >outputs should I expect at, for example, the H3/H4 winding with a voltage on >H1/H2 winding? How to identify backward connection of a winding? > >Are the two H windings identical? The two X windings? > >Suggestions welcome. > >This is a 208 -> 230 (ie, 12 & 24 v buck-boost voltage) single-phase >autotransformer in N. America. > >Thanks.
Well, you'd expect the 12/24V windings to be MUCH lower resistance than the primary. If the 12/24 is a center-tapped winding, the 0..12 may be lower resistance (wound from fatter wire) than the 12:24 winding. You could fire it up with a light bulb in series and measure the voltages.
On Tue, 11 Feb 2014 13:07:35 -0800, Joerg <invalid@invalid.invalid>
wrote:

> >Oops, if yours is not an "electronic transformer" disregard the above. >But then it's not really buck/boost.
Buck-boost in this context refers to an electrical transformer that has the primary attached across the mains, and the secondary either boosts or bucks the mains voltage depending on whether it's connected in phase or out of phase. It has an advantage over (say) a 240:208 tranformer in that the core size can be much smaller. --sp