# Ferroresonant (Constant Voltage) transformers

Discussion in 'General Electronics Chat' started by Anomaly, Jan 9, 2004.

1. ### Anomaly Thread Starter New Member

Jan 9, 2004
6
0
This is my first attempt at posting so bear with me. I'm interested in understanding the principles governing the sizing of capacitors used in ferroresonant or constant voltage transformers. I've recently experienced the failure of a transformer used in a battery charger circuit that overheated (read burned up) and believe it was due to the size of the capacitor. If I understand the relevant principles, it was oversized by a factor of 4. I have read the section in chapter 9 which shed quite a bit of insight, but I would like some examples illustrating the same circuit with different size caps. I'll express my gratitude now for any responses. Thanks, Anomaly :unsure:

2. ### mozikluv AAC Fanatic!

Jan 22, 2004
1,437
1
:huh: hi,

would you care to post the schem of your circuit so appropiate response can be given?

3. ### Anomaly Thread Starter New Member

Jan 9, 2004
6
0
I'm not sufficiently familiar with the methods of posting a schematic, but I'll describe in more detail. The application uses a dual winding transformer core, one winding (primary and secondary) serve as control power (480v / 120v) the other winding (same core) is for battery charging. The primary of unknown voltage and configuration employs a capacitor, the secondary serves the battery charger load @ 42v AC. The 42v AC is then fed to two different battery chargers, one a 24v system, the other a 12v system. Transformer rating is 500va control winding and 500va constant voltage, flux coupled, charging winding. I'll work on learning the in's & out's of schematic postings. Thanks for the interest...

4. ### mozikluv AAC Fanatic!

Jan 22, 2004
1,437
1
hi,

here is a formula you can use as a guide to compute for your capacitance rating:

uf = [(I * 1.0^6 / 1.5) * (8.3^-3)]

for capacitor working voltage (WV)

WV = 1.414 * Vs

hope this can help