John T Electrical question

I have a couple questions for John or the electrical guru’s on here,
I have a table top magneto magnetizer that operates on 120v ac. It wasn’t working well so opened it up. Inside it has two start capacitors rated at 161-190 MFD, 110vac. This appears to be a capacitor discharge circuit. Along with that is a large diode converting the ac to dc.
After testing I was convinced that one capacitor was out of range. So I temped in two new ones and the problem was solved. They were wired in parallel. The question I have is, there anything gained from adding a third or fourth capacitor? There is more than enough room as the new ones are much smaller. Or does this through off the rest of the unit?

Been many years since I did much in electronics but if I remember right it would hurt you not help you since a capacitor is sort of like a fast discharge battery and it charges up then discharges so as to give a bigger kick of volts to start up things. Used very simple terms here by the way

SORRY I JUST CANT ANSWER THE QUESTION EXACTLY BUTTTTTTTT I DO HAVE SOME THOUGHTS FWIW

Not knowing the entire circuit and how it functions I cant say for sure, maybe the more electronic (Im more into AC Power Distribution then electronics) gents here or those familiar with a magneto charger can enlighten us??? I do know they have to supply a heavy discharge of DC current for a really strong magnetic field in order to magnetize the mags rotor.

For example, the Capacitors could be used to smooth out and filter the badly pulsed DC wave that results from a diode and half wave rectification??? (But I sorta doubt thats how they are used in your unit, unfiltered pulsing DC is still DC current)

The capacitors (Im sorta thinkin this is how your unit works) could be used to store energy and then provide the capacitor discharge form of sudden released current energy kind of like you seem to be thinking (you metioned capacitor discharge)

If the above is their function, simply to store energy, the more in paralell and/or the higher capacitance rating, the more instantaneous current they could dump to create an even stronger magnetic field !!!!!!!!!!!! HOWEVER you have to match that with the current and capacity the rectifier circuit can produce so once the capacitors are discharged and the rectifier circuit starts to pump current into them the rectifier part of the circuit and the diodes current rating isnt exceeded (cuz theres just toooooo muchhhhhhh capacitance) and you end up frying things!!!!!!!!!

MY BOTTOM LINE BEST "GUESS" IS GONNA BE WHILE THE EXACT CAPACITANCE ISNT NECESSARY AND A TAD MORE WONT HURT,,,,,,,,,IM AFRAID IF THERES TOO MUCH CAPACITANCE YOU MIGHT OVERCURRENT AND DAMAGE THE RECTIFIER CIRCUIT!!!!!!!!

THIS IS NOT AN ANSWER REMEMBER ONLY MY BEST GUESS SO DONT ANYONE HAVE A CALF NOW LOL

John T

Hello,
Capacitors in series adds up the value.
Two 10 MFD's caps in series would be 20 MFD'S
So if you want to add capacity, you need to put the extra caps in series in the circuit.
Make sure they are rated at the same voltage,
You could try it and see what happens. Just don't let the smoke out, I do it quite often!
Guido.

If the caps are after the diode, then they store the dc pulses. Measure the volts on the caps before you are turn on the magnitizer current, they will charge to the peak volts, which is around 155v dc. If you research 1/2 wave power supply, the two caps are storing the dc voltage. Two caps in parallel is just like putting two batteries in parallel, they will store more electrons and be able to produce more current when discharged.

If you want to prove the big bang theory, put many caps in parallel, unplug from the 120vac and see how many metal particles come off the tip of your screwdriver when you short out the caps. Don't do this if you are on a pacemaker. It would be a very good idea if you are holding on the the insulated end of the screwdriver too.

George

Sorry Guido--not correct Capacitor in series increase the voltage rating and do not double the capacitance.

Actually, capacitors in PARALELL (NOT series) are additive. If you place two 10 MFD in paralell, you now have 20 MFD.

John T

(quoted from post at 16:18:10 12/12/12) MY BOTTOM LINE BEST "GUESS" IS GONNA BE WHILE THE EXACT CAPACITANCE ISNT NECESSARY AND A TAD MORE WONT HURT,,,,,,,,,IM AFRAID IF THERES TOO MUCH CAPACITANCE YOU MIGHT OVERCURRENT AND DAMAGE THE RECTIFIER CIRCUIT!!!!!!!!
John T

Click to expand...

Hey John T - Those are my thoughts exactly!

A bit more capacitance won't hurt. But adding too much (ie. an additional cap) risks damage to the rectifier circuit when the unit charges due to the higher inrush current it must now handle.

ALSO......increasing capacitance beyond design translates into much greater peak current pulses when the caps discharge. This MAY damage other parts in the circuit. Further, it could become a life safety issue should you accidentally contact the fully-charged capacitor bank or the output wiring.

I'd replace the caps with the same capacitance value and leave it alone.

Bob M, the retired ME.

Hey if BOTH a Mechanical and an Electrical Enginner agree........WE ARE SURELY RIGHT LOL

John T

There are so many things to consider when designing circuitry. In-rush current, charge transfer, wattage rating of down stream components. Without looking at the circuit in detail it is hard to give a good opinion.

I will agree with Bob, Same capacitance, same voltage, leave it alone.

Cliff(VA)
Active EE circuit designer

Hello John T,
I know it was the opposite of resistors, and still got it wrong! Thanks for the correction.
There is enough info on this forum that is way off. Me and the rest of the wifes tale people need a spot check now and then.
Good sparking with you!
Guido.

Heck I still get things wrong I knew (thought I did lol) for years.....I have learned on here, been corrected a few times myself, but thats how we ALLLLLLLLLL learn.......Kinda like the Bible story about he who is without sin casting the first stone, I dont think I'll be throwing any.

John T

Hello John T
Like I said, I sure know how they work and use them in many ways. Lots of times let all the smoke out. But................ that was just wrong info on my part. No stone casting on my end! Anyhow I hope to retun the favor. I'll be watching you! Ha1 Ha1.....
Guido.