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Registered Member #3603
Joined: Tue Jan 11 2011, 11:21PM
Location:
Posts: 11
I am trying to charge a cap bank to 415v. I have scavenged a MOT. The original primary has 106 turns. I pulled out the old secondary. I want to use the old primary as the charging secondary, so I wound 46 turns in magnet wire as a new primary.
Testing: I tried running it backwards (step down) first in case I did something horribly wrong. 120vAC in, I predicted 50 out, I measured 47 which I think is pretty good considering how inefficient MOTs are.
Then I tried it forwards. Put 120 in, measured 126 out before I popped a 15A circuit breaker in the powerstrip it was plugged in to.
I don't understand why it wasn't giving me like 310 out (which is what I want, Ill rectify to ~415). Any suggestions for how to troubleshoot this?
Or should I just scrap it and build a boost converter? I am on a deadline, I have about 2 weeks to finish this project.
Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
well there's no need to scrap it yet. it could be used for other projects for a low voltage, high current source. unless you want to try wrapping 240+ turns on the core and using it as your secondary, then a boost converter is probably a good alternative (esp. considering the deadline)
Registered Member #1316
Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365
The MOT core has a maximum value of volts/turn or else the core will saturate, drawing excessive current, and in your case, blow breakers. The number of turns for the current primary is close to this maximum. You can't wind a new primary with less turns. If you want a higher voltage, you will have to wind a new secondary and keep the original primary as a primary.
Registered Member #3603
Joined: Tue Jan 11 2011, 11:21PM
Location:
Posts: 11
Thank you for the quick replies, both helped very much. I believe I will order parts today for a boost converter seeing as I have several good 12v power supplies.
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Should I scrap this MOT?
