Transformer or inductor?

Pliers · 2012-01-25 13:21

Im trying to understand what T2 is doing in this schematic.
It does not look like it is being used as a transformer. It looks like it is being used as a pair of inductors. I will probably build this and try individual inductors and see what the results are.
This circuit was designed in the mid 1990s. The company does support the equipment and Im building replacement boards. I can copy a circuit and not know how it works, but I like to know.
The failure of the control board, not generally involved with this circuit, causes many burnt lands and destroyed components.

Phil Pilgrim (PhiPi) · 2012-01-25 13:43

It's definitely a transformer, since the two windings share a common core. But it looks like it's being used as a common-mode choke of some sort.

-Phil

Pliers · 2012-01-25 15:44

Phil, I think you are right about it being used as a common mode choke.
Thanks for the insight.

frank freedman · 2012-01-25 17:45

Pliers wrote: »

I’m trying to understand what T2 is doing in this schematic.
It does not look like it is being used as a transformer. It looks like it is being used as a pair of inductors. I will probably build this and try individual inductors and see what the results are.
This circuit was designed in the mid 1990s. The company does support the equipment and I’m building replacement boards. I can copy a circuit and not know how it works, but I like to know.
The failure of the control board, not generally involved with this circuit, causes many burnt lands and destroyed components.

I believe after looking at the circuit that the T2 component is being used as an inductor in an LC tank circuit. Note that if you redrew the circuit, you would find that you have an LC tank circuit placed across the unfiltered full wave circuit formed by the rectifiers. If your meter reads inductance, it would be interesting to see how the pwm frequency stacks up against the calculated resonant frequency of the tank. Maybe clip the cap and see what the effect on the output is. Looks like the tank circuits are being used as high frequency filtering.

Out of curiosity, is the isolated power supply being used for biasing high power switching circuits?

Frank Freedman

Phil Pilgrim (PhiPi) · 2012-01-25 18:34

For it to be an LC tank circuit (i.e. notch filter) there would have to be a cap in parallel with the winding. There is none.

-Phil

kwinn · 2012-01-25 19:51

Have to agree with Phil. Definitely used as a choke.

frank freedman · 2012-01-25 20:46

Phil Pilgrim (PhiPi) wrote: »

For it to be an LC tank circuit (i.e. notch filter) there would have to be a cap in parallel with the winding. There is none.

-Phil

eh, time to go get my prescription filled. I guess Lens Crafters or Costco. Who ever turns em faster. Thought the filter cap was across the T2 winding........

As Homey would say mmmmmmmmmmm doughnut... er, I mean DDDOOOOOOHHHH!!!!!!!!

FF

Can one post chars using overstrike on here??

Phil Pilgrim (PhiPi) · 2012-01-25 20:50

frank freedman wrote:

Can one post chars using overstrike on here??

Sure. (I have to do it a lot!) Use the [noparse] and [/noparse] tags.

-Phil

Pliers · 2012-01-26 06:35

Hey Frank. To answer your question about it use

Out of curiosity, is the isolated power supply being used for biasing high power switching circuits?

.
One of the 20 volts is regulated down to 15 volts to be used by the computer interface.
The other 20 volts is used by the control section of a power factor circuit and a buck controller.
The output of the supply is 150 volts DC at 44 amps.

frank freedman · 2012-01-26 22:28

'splains the isolation.

FF

Transformer or inductor?

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