I have four 400 pf doorknob caps rated at 30 KV laying in a drawer that I could use with some suitable HV resistors. Can anyone suggest a topology and component values?
----- Original Message -----
From: "Bert Hickman" <bert@xxxxxxxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, February 6, 2018 12:10:05 AM
Subject: Re: [TCML] Pole transformer protection
Steve,
Distribution transformers are not impervious to damage, especially when
subjected to high voltage transients with very fast rise- or fall-times.
Fast HV transients excite portions of the winding, especially the turns
near to an output terminal. This can overstress, and eventually destroy,
the insulation between the last few turns, or the insulation between
the outermost winding and the winding layer below. I am aware of at
least two instances where coilers on this list have destroyed their
distribution transformers.
A suitably rated low-pass RC protection network will slow down, and
dissipate, the fast transients and VHF ringing that occur when your
spark gaps fire. Consider it cheap insurance.
Bert
Steve White wrote:
> I know this is an old question but I have searched the archives and have not found a definitive answer. Does my pole transformer need protection? Some say use a low-pass filter and some say you don't need it because pole transformers are so rugged. My pole transformer is a 14.4 KV unit with a 10 KVA power rating. My coil uses a SRSG spinning at 3600 RPM with 4 flying electrodes so that the tank circuit fires 4 times per 60 Hz cycle. My adjustable air gap inductive ballast is set to allow no more than 20 amps to the tesla coil. I am using 240 volts so my wall power is about 4.8 KVA. I get 7 - 8 foot sparks. I am satisfied with the performance and have run it for a total of about 2 hours. I currently have no protection or filtering of any kind between my pole transformer and the tesla coil other than a safety gap.
>
> Do I need some sort of protection other than the safety gap for the pole transformer? Given how hard it is to obtain these nowadays, I do not want to accidentally destroy it.
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