Transformer question?

[buildingnut]

I remember reading a thread on here about someone ( forgive me if I screw up the wording) re varnishing a transformer? Are any of you guys that are building these WOPL'S doing
anything with the transformers other than cleaning and repainting the covers? Just curious? I searched for the thread but could not find it. I swear I remeber as I thought that part of the procedure was the guy stuck it in the oven which I thought was weird. And no I have not smoked anything green and leafy... Yet

 

[Gepetto]

I remember reading a thread on here about someone ( forgive me if I screw up the wording) re varnishing a transformer? Are any of you guys that are building these WOPL'S doing
anything with the transformers other than cleaning and repainting the covers? Just curious? I searched for the thread but could not find it. I swear I remeber as I thought that part of the procedure was the guy stuck it in the oven which I thought was weird. And no I have not smoked anything green and leafy... Yet

Hi Trevor.

The transformers are built by stacking up very thin laminations to make what is called an E-I core transformer.

Each lamination is insulated from the adjacent lamination by a varnish that acts like an insulating coating separating it electrically from the other laminations in the core stack. This technique reduces eddy current losses in the transformer which are just wasted energy and stray magnetic flux.

After the entire transformer is assembled and wound, they are typically varnish dipped in a vacuum chamber to vacuum impregnate the entire structure which eliminates vibration from the 60 Hz energizing current, reducing noise.

Why do I tell you all this? If you refinish the core, do it gently so you do not inadvertently break down the insulation of the lamination to lamination that is built into the design of this transformer.

 

[buildingnut]

Hi Trevor.

The transformers are built by stacking up very thin laminations to make what is called an E-I core transformer.

Each lamination is insulated from the adjacent lamination by a varnish that acts like an insulating coating separating it electrically from the other laminations in the core stack. This technique reduces eddy current losses in the transformer which are just wasted energy and stray magnetic flux.

After the entire transformer is assembled and wound, they are typically varnish dipped in a vacuum chamber to vacuum impregnate the entire structure which eliminates vibration from the 60 Hz energizing current, reducing noise.

Why do I tell you all this? If you refinish the core, do it gently so you do not inadvertently break down the insulation of the lamination to lamination that is built into the design of this transformer.

Thanks for the explanation Joe! I was pretty certain that nobody was doing anything other than cleaning and repainting. Thank you!

 

[WOPL Sniffer]

YUP, disassembling the transformer is asking for trouble.

 

[Northwinds]

I wonder if that is why one of Lee's 700 series 1's vibrates when it's on. I tried tightening the bolts like he said but it has a hum/vibration still

 

[laatsch55]

Pretty much depends on what the oscillation frequency is.....

 

[Northwinds]

Lee, it sounds like one of those old electric heaters when it's turned on

 

[laatsch55]

I've had that a couple times, never did find it....label is on the way....

 

[orange]

I had THREE HK CAD-5 cassette decks (Nakamichi chassis) and every single one developed a hum in the transformer.

 

[wattsabundant]

My fist real job was at a transformer shop. Hated it. Transformers are boring. learned more than I ever wanted to know about them. Swore I'd never touch one again. 35 years later and I'm still working with them albeit much larger.

As Joe mentions the laminations are insulated. I'm not sure what the coating is, but it's not the traditional varnish. The vacuum pressure impregnation (VPI) process is an expensive process usually found in larger transformers. The shop I worked at did not use VPI. Instead, there were tanks of resin about 3' x3' that the transformers were dipped in. Then they were baked in an oven.

The resins used are for temperatures in the 200C range. It's not likely they can be found locally. If someone has a loud transformer it's possible to get it redipped and baked at a motor rewind shop which may help. however, doing so introduces contaminations into the resin. For this reason my current employer will not redip a transformer.

Here is a link to our web page with a document on the VPI process. It's the second one from the bottom. http://www.solidstatecontrolsinc.com/News/technical-papers.aspx

 

[buildingnut]

My fist real job was at a transformer shop. Hated it. Transformers are boring. learned more than I ever wanted to know about them. Swore I'd never touch one again. 35 years later and I'm still working with them albeit much larger.

As Joe mentions the laminations are insulated. I'm not sure what the coating is, but it's not the traditional varnish. The vacuum pressure impregnation (VPI) process is an expensive process usually found in larger transformers. The shop I worked at did not use VPI. Instead, there were tanks of resin about 3' x3' that the transformers were dipped in. Then they were baked in an oven.

The resins used are for temperatures in the 200C range. It's not likely they can be found locally. If someone has a loud transformer it's possible to get it redipped and baked at a motor rewind shop which may help. however, doing so introduces contaminations into the resin. For this reason my current employer will not redip a transformer.

Here is a link to our web page with a document on the VPI process. It's the second one from the bottom. http://www.solidstatecontrolsinc.com/News/technical-papers.aspx

Thank you for the information, interesting read.

 

[WOPL Sniffer]

I wonder if that is why one of Lee's 700 series 1's vibrates when it's on. I tried tightening the bolts like he said but it has a hum/vibration still

Thought one of my amps had a hummmm. Tightened it, tightened it again, then I figured out it was my soldering station right behind the amp on My bench humming away..... duh?

 

[Gepetto]

It is also important to put insulating washers on the through bolts to insulate them from the core or eddy currents and noise may result from these currents being developed in the bolts.

 

[laatsch55]

As in " sleeves" to cover the entire bolt??

 

[grapplesaw]

As in " sleeves" to cover the entire bolt??

Yes phase linear used the " Dixie cup Straw" with red strips in two of my dual 500 as insulator.

 

[laatsch55]

Joe mentioned this to me a couple years ago and it never sunk in that could be the root of some very persistent chassis vibrations....

 

[laatsch55]

Glen, here is a pic of the +/- 108 volt DC rail voltage 400 transformer. It does not have a 6 volt secondary winding........bad day at the transformer shop....

 

[grapplesaw]

Glen, here is a pic of the +/- 108 volt DC rail voltage 400 transformer. It does not have a 6 volt secondary winding........bad day at the transformer shop....

Thanks Lee
I will see if I can come up with a way to use it. It may be overkill anyway. Have to add a second 12 volt transformer for the meters then to make it work. Let you know soon
thanks

 

[grapplesaw]

Lee I will let you know in a day or so. I will see if I have room in the smaller chassis for a second transformer.

 

[Northwinds]

Glen, here is a pic of the +/- 108 volt DC rail voltage 400 transformer. It does not have a 6 volt secondary winding........bad day at the transformer shop....

108v HOLY SHIT. My 700 is 106v LMAO!!!