lørdag den 27. juni 2020 kl. 16.59.09 UTC+2 skrev amdx:> On 6/27/2020 9:36 AM, jlarkin@highlandsniptechnology.com wrote: > > On Sat, 27 Jun 2020 09:31:08 -0500, amdx <nojunk@knology.net> wrote: > > > >> I thought I could remove the secondary and the shunts, then install a > >> new secondary and have a low voltage transformer, maybe not. > >> I removed the HV secondary, Then wound 10 turns and got 8 volts. > >> I loaded it with 2 ohms, all is well except the PF is 0.15. > >> I will need to have about 25 turns to get my 20 Volts, but, do I need to > >> do something about the PF? Why is it so low? > >> I expect Phil will set me straight on this. > >> > >> Thanks, Mikek > > > > Microwave transformer? > > > > I think they are designed to have a lot of leakage inductance. > > > > > > > I thought the shunts had something to do with that? > That's why I removed them.it is a mass produced item made with the absolute minimum of materials to not self destruct when fan cooled and used for short times as usual with a microwave
Rewiinding a MOT
Started by ●June 27, 2020
Reply by ●June 27, 20202020-06-27
Reply by ●June 27, 20202020-06-27
On 2020-06-27, amdx <amdx@knology.net> wrote:> On 6/27/2020 4:19 PM, Jasen Betts wrote: >> On 2020-06-27, amdx <nojunk@knology.net> wrote: >>> I thought I could remove the secondary and the shunts, then install a >>> new secondary and have a low voltage transformer, maybe not. >> >>> I removed the HV secondary, Then wound 10 turns and got 8 volts. >>> I loaded it with 2 ohms, all is well except the PF is 0.15. >> >> You've increased the magnetic resistance by removing the shunts so now >> it's running further into partial saturation, you can maybe fix that by >> adding some primary turns, the core is built with E and I stacked >> instead of interleaved this makes for more gap which probably isn't >> helping either. >> >> At low loads magnetising current will dominate the current draw, giving >> low power factor. >> >>> I will need to have about 25 turns to get my 20 Volts, but, do I need to >>> do something about the PF? Why is it so low? >>> I expect Phil will set me straight on this. >> >> If you're running a rectifier into a capacitor PF will be low because >> conduction angle, This can be improved by putting a choke between the >> rectifier and the capacitor. >> > > So I need to add more turns to the primary, 20% and also the primary > is designed for about 1000 watts. I loaded it with about 35 watts, so > most of the primary current was magnetizing current. > The end result will be say 22 volts @ 8 amps, about 175 watts, about > 18% of the primary designed capacity. > Should I add more that 20% to the primary?After you end saturation the extra effort is wasted, if you have a variac and a current transformer, or current probe, you could turn the voltage down and look for the voltage where saturation is curtailed, and then scale existing the turns count up from there to at-least meet the maximum line voltage spec (126V) 20% should easily get you there. As you're going to be running a motor the capacitor is not needed, so neither is the choke. Be sure to use an over-sized rectifier to handle the stall current. -- Jasen.
Reply by ●June 27, 20202020-06-27
amdx wrote:> I thought I could remove the secondary and the shunts, then install a > new secondary and have a low voltage transformer, maybe not. > I removed the HV secondary, Then wound 10 turns and got 8 volts. > I loaded it with 2 ohms, all is well except the PF is 0.15. > I will need to have about 25 turns to get my 20 Volts, but, do I need > to do something about the PF? Why is it so low? > I expect Phil will set me straight on this.Many years ago I asked Win for a chapter on this.
Reply by ●June 27, 20202020-06-27
amdx is persistantly stupid wrote: ===================================> > I removed the HV secondary, Then wound 10 turns and got 8 volts. > I loaded it with 2 ohms, all is well except the PF is 0.15.** So you put a 30 watt load on a 1kW, saturating supply tranny and expected a good PF ???> I expect Phil will set me straight on this.** Sure thing, but not the Phil you wanted. As Mrs Cooper famously said: "dumb as soup" . .... Phil
Reply by ●June 27, 20202020-06-27
On 6/27/2020 8:02 PM, Phil Allison wrote:> amdx is persistantly stupid wrote: > > =================================== >> >> I removed the HV secondary, Then wound 10 turns and got 8 volts. >> I loaded it with 2 ohms, all is well except the PF is 0.15. > > > ** So you put a 30 watt load on a 1kW, saturating supply tranny and expected a good PF ??? > > >> I expect Phil will set me straight on this. > > > ** Sure thing, but not the Phil you wanted. > > As Mrs Cooper famously said: "dumb as soup" . > > > .... Phil >No you are the Phil I expected and I got the usual reaction. You have made a lot of comments about transformers over the years so I expected you would have some good info. If you could just get past your personality! Mikek -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
Reply by ●June 27, 20202020-06-27
On Saturday, June 27, 2020 at 9:40:53 PM UTC-4, amdx wrote:> On 6/27/2020 8:02 PM, Phil Allison wrote: > > amdx is persistantly stupid wrote: > > > > =================================== > >> > >> I removed the HV secondary, Then wound 10 turns and got 8 volts. > >> I loaded it with 2 ohms, all is well except the PF is 0.15. > > > > > > ** So you put a 30 watt load on a 1kW, saturating supply tranny and expected a good PF ??? > > > > > >> I expect Phil will set me straight on this. > > > > > > ** Sure thing, but not the Phil you wanted. > > > > As Mrs Cooper famously said: "dumb as soup" . > > > > > > .... Phil > > > > No you are the Phil I expected and I got the usual reaction. > You have made a lot of comments about transformers over the years > so I expected you would have some good info. > If you could just get past your personality! > MikekWhy would you expect Phil to be able to get past his own personality when no one else can? -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
Reply by ●June 27, 20202020-06-27
amdx puked: ===========> >> I removed the HV secondary, Then wound 10 turns and got 8 volts. > >> I loaded it with 2 ohms, all is well except the PF is 0.15. > > > > > > ** So you put a 30 watt load on a 1kW, saturating supply tranny and expected a good PF ??? > > > > > >> I expect Phil will set me straight on this. > > > > > > ** Sure thing, but not the Phil you wanted. > > > > As Mrs Cooper famously said: "dumb as soup" . > > > > > > .... Phil > > > > No you are the Phil I expected and I got the usual reaction. >** Precise and clear, unlike you.> You have made a lot of comments about transformers over the years > so I expected you would have some good info.** Then use " Phil A"> If you could just get past your personality!** Take a look in the mirror, sunshine - you have the personality and IQ of a demented chimp. .... Phil
Reply by ●June 27, 20202020-06-27
Reply by ●June 27, 20202020-06-27
On Saturday, June 27, 2020 at 10:47:17 PM UTC-4, Michael Terrell wrote:> All your PF are belong to us!I'm trying to imagine the picture to go with that! -- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
Reply by ●June 28, 20202020-06-28
On 6/27/2020 3:10 PM, Tim Williams wrote:> Well yeah, you loaded it to a teensy fraction of its load capacity. > > Protip: put +20% turns on the primary to reduce saturation.� All your PF > is going into harmonics. > > Tim >isn't there a rule of thumb about MOTs that if you have to ask you probably shouldn't be messing with MOTs I have a confession to make, I don't think I've ever thought messing with MOTs would be a productive use of my time. sometimes I feel like those things are catnip to electronics dudes I don't get it.
