# [TCML] confused

Reuben Marcus rmferaligator at aol.com
Wed Jun 18 15:34:22 MDT 2008

```You are incorrect in saying there is no such thing as dc transformers they do exist they pulse dc to simulate ac

Reuben
Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Quarkster <quarkster at att.net>

Date: Wed, 18 Jun 2008 13:05:58
To:Tesla Coil Mailing List <tesla at pupman.com>
Subject: Re: [TCML] confused

Douglas -

Maybe more confusion than you realize .....

First, transformers are alternating current (AC) devices; there is no such thing as a "DC" transformer. The basic operating principle of a transformer relies on rapidly changing magnetic fields, which are generated by an AC current. A transformer utilizes an AC input, and provides an AC output. You can rectify the output of a transformer to obtain DC, but the output of a transformer will always be AC.

Second, you mention "power factor" as "the major rule of thumb" in designing a tesla coil. Perhaps you are thinking that "power factor" is a measure of Tesla coil efficiency, or output. This is incorrect. "Power factor" is a means of quantifying the phase relationship of the current and voltage in an AC circuit. JAVATC is providing information on the power factor of the HV supply transformer (frequently a NST). The effects of "power factor" on the operation of a typical Tesla coil are quite small, but could play some small role if you are using a long extension cord, or are running a coil that is drawing sufficient current to be very near the trip point of your home's circuit breaker. Wikipedia has a description of power factor at: http://en.wikipedia.org/wiki/Power%5Ffactor

Much more important in Tesla coil design and operation are the losses in the tank circuit (spark gap, tank capacitor, primary coil and its connections) and the basic tuning of the coil to obtain primary/secondary resonance. Assuming an NST-powered coil, once the coil is up and running well you can experiment with adding Power Factor Correction (PFC) capacitors on the AC input side of the NST to reduce "apparent" current draw.

Regards,
Herr Zapp

douglas smith <eyemfedup2 at yahoo.com> wrote:
all this talk about hooking  ac transformers in series has got me really confused.
i always thought  that you could connect DC output transformers in series
but not AC.
i know that there is some kind of circuit that allows you to do so but just
putting two nst's in series sounds like trouble to me.
why would you want to anyway?
in designing some 15 different possible coils with javatc it seems to me that
a higher voltage is not always that necessary.
example: i would get the same spark length and power factor with using a
15000 v @ 30 ma as i would with a 7500 v @ 60 ma
of course I'm no expert the math just seems the same (P=I x E) and also with javatc
I'm sure that there is a limit on how low you can go with the voltage vs. current
but it does seem to me that the major rule of thumb is the power factor.

_______________________________________________
Tesla mailing list
Tesla at www.pupman.com
http://www.pupman.com/mailman/listinfo/tesla

_______________________________________________
Tesla mailing list
Tesla at www.pupman.com
http://www.pupman.com/mailman/listinfo/tesla
```