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Make your own Power Transformer

Started by Unknown January 13, 2019
I watched a youtube video of a guy winding his own power transformer. He
used a pre-made plastic bobbin, wound the enameled wire as needed, and
put in the steel laminations. 

Apparently he bought that bobbin, and the laminations to fit it. Is
there a place that sells that sells the parts (bobbin and laminations)?

On Monday, 14 January 2019 02:03:23 UTC, tub...@myshop.com  wrote:

> I watched a youtube video of a guy winding his own power transformer. He > used a pre-made plastic bobbin, wound the enameled wire as needed, and > put in the steel laminations. > > Apparently he bought that bobbin, and the laminations to fit it. Is > there a place that sells that sells the parts (bobbin and laminations)?
If you're just after a 1 off, you could take a mains transformer & cut the secondary wind out. Cost nothing, done in 10 minutes. NT
Yup.
https://www.edcorusa.com/

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

<tubeguy@myshop.com> wrote in message 
news:1frn3eh83ludqvt1l2td109bmj9i3minua@4ax.com...
>I watched a youtube video of a guy winding his own power transformer. He > used a pre-made plastic bobbin, wound the enameled wire as needed, and > put in the steel laminations. > > Apparently he bought that bobbin, and the laminations to fit it. Is > there a place that sells that sells the parts (bobbin and laminations)? >
> If you're just after a 1 off, you could take a mains transformer & cut the secondary wind out. Cost nothing, done in 10 minutes. > > > NT >
I have repurposed microwave oven transformers & have always had awful hum. Is that a problem with all homemade transformers? If not, what makes the difference? I did quiet them somewhat by using wooden wedges between the added winding and the core.
onsdag den 16. januar 2019 kl. 18.42.36 UTC+1 skrev Bob Engelhardt:
> > If you're just after a 1 off, you could take a mains transformer & cut the secondary wind out. Cost nothing, done in 10 minutes. > > > > > > NT > > > > I have repurposed microwave oven transformers & have always had awful > hum. Is that a problem with all homemade transformers? If not, what > makes the difference? I did quiet them somewhat by using wooden wedges > between the added winding and the core.
back when I was in school and had to wind and assemble a transformer it was dipped in lacquer and baked after assembly
On 1/16/2019 11:41 AM, Bob Engelhardt wrote:
>> If you're just after a 1 off, you could take a mains transformer & cut >> the secondary wind out. Cost nothing, done in 10 minutes. >> >> >> NT >> > > I have repurposed microwave oven transformers & have always had awful > hum.&nbsp; Is that a problem with all homemade transformers?&nbsp; If not, what > makes the difference?&nbsp; I did quiet them somewhat by using wooden wedges > between the added winding and the core. >
I have wound a few transformers, I ask my local motor rewind company for a quart of the lacquer they use when they rewind motors. A soaked the transformer in the lacquer let it drip a bit and baked at low temp in a toaster oven. Also made a coil for a 120V generator the same way. I had some experience, I worked in a motor rewind company in the early 80s. Dirty, hard work, but I'm glad I had the experience. I got laid off in an economic turn down, they did a lot of work for the auto manufacturers, and when the slowed, we slowed, more. Mikek
Bob Engelhardt wrote:

>> > > I have repurposed microwave oven transformers & have always had awful > hum. Is that a problem with all homemade transformers? If not, what > makes the difference? >
** Microwave oven transformers are very specialised for that job. Consider that they rely on constant fan cooling, operate under a heavy load ( an overload really) ALL the time and emit considerable audible hum while being used in the oven. When repurposed and lightly loaded, the core is in permanent saturation. OK for a C&N spot welder I guess. .... Phil
On Wednesday, 16 January 2019 17:42:36 UTC, Bob Engelhardt  wrote:

> > If you're just after a 1 off, you could take a mains transformer & cut the secondary wind out. Cost nothing, done in 10 minutes.
> I have repurposed microwave oven transformers & have always had awful > hum. Is that a problem with all homemade transformers? If not, what > makes the difference? I did quiet them somewhat by using wooden wedges > between the added winding and the core.
Microwave transformers are different to all others. Yes they hum plenty. They also overheat in 15 minutes & have shorted laminations, creating inductance on the output. I've only seldom made mains transformers, not had any hum problem. NT
Bob Engelhardt wrote:
>> If you're just after a 1 off, you could take a mains transformer & cut >> the secondary wind out. Cost nothing, done in 10 minutes. >> >> >> NT >> > > I have repurposed microwave oven transformers & have always had awful > hum.&nbsp; Is that a problem with all homemade transformers?&nbsp; If not, what > makes the difference?&nbsp; I did quiet them somewhat by using wooden wedges > between the added winding and the core. >
Microwave oven transformers (MOT's) are intentionally made to be inexpensive. Since the manufacturers skimp on iron and copper (or aluminum), they run close to saturation under light or no load. It's not unusual to see 3-4A of primary magnetizing current on a 120 volt MOT with no load. One other feature of these transformers is the addition of magnetic shunts in the magnetic circuit between the primary and secondary windings in order to add significant leakage inductance. This helps to limit fault current during arcing within the magnetron or the oven cavity. If you don't remove these shunts, your repurposed transformer will have relatively poor voltage regulation under load. Adding additional turns to the primary and knocking out the magnetic shunts will make these transformers more efficient in a repurposed application.
"Bert Hickman" <bert-hickman@comcast.net> wrote in message 
news:3uydnW0svNh3CKLBnZ2dnUU7-InNnZ2d@giganews.com...
> Adding additional turns to the primary and knocking out the magnetic > shunts will make these transformers more efficient in a repurposed > application.
Indeed. Consider adding about 20% more primary turns, and consider reducing the total VA capacity to maybe 60% of the oven's nameplate rating. That'll get you a transformer that runs cool, or at least as cool as the core will allow (which by the way, isn't too bad, because the core stack is welded across the outside -- this doesn't create shorted turns, it creates a book with a single spine; if the book were bound twice with two spines, there would be a shorted loop). A properly made ~400VA transformer will be smaller than an MOT thusly repurposed, but you're not complaining because you got it for free out of the trash. ;-) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/