Help With Circuit Information??

[Randy Gross]

Please view in a fixed-width font such as Courier.

________________
| _____|_____
______ | | | R1 and R2 used as a
)|| __| | |
120vac )||(8vac R1 R2 test load to
)||(7 Turns 14 Ohms 21 Ohms
6A )||(__ | | determine output amps.
______)|| | | |
| |___________|
50 Turns |________________|


This schematic depicts a transformer under load for testing purposes. I
scoured the web in search of a high current dummy load, no luck! I came up
with the Idea of using 2 heating elements (R1 and R2) wired in parallel to
reduce the total load resistance.

The result was surprising. I expected a good deal of heat but, the elements
didn't even warm. The drawback is, how do I use the resulting data to
determine the actual circuit amperage. These are the figures:

OCV: 8.1v
Total secondary load resistance: 8.5 ohms
Secondary current (clamp-on meter): 1.02 Amps
Primary current under load: 8.3 Amps

SOS

--

An Inquiring Mind
Randy Gross
----------------------------------------------------------
<') >< Homebuilt Arc Welders >< ('>
http://www.gomedia.ca/~aaawelder/
Chance favors the prepared mind whose hands do the work!

 

[Bill Bowden]

"Randy Gross" <rgwg99@acsplus.com> wrote in message news:<01c368c2$0528a600$442525d8@dialup>...

Please view in a fixed-width font such as Courier.

________________
| _____|_____
______ | | | R1 and R2 used as a
)|| __| | |
120vac )||(8vac R1 R2 test load to
)||(7 Turns 14 Ohms 21 Ohms
6A )||(__ | | determine output amps.
______)|| | | |
| |___________|
50 Turns |________________|


This schematic depicts a transformer under load for testing purposes. I
scoured the web in search of a high current dummy load, no luck! I came up
with the Idea of using 2 heating elements (R1 and R2) wired in parallel to
reduce the total load resistance.

The result was surprising. I expected a good deal of heat but, the elements
didn't even warm. The drawback is, how do I use the resulting data to
determine the actual circuit amperage. These are the figures:

OCV: 8.1v
Total secondary load resistance: 8.5 ohms
Secondary current (clamp-on meter): 1.02 Amps
Primary current under load: 8.3 Amps

SOS

I don't think you have enough turns on the primary, 8.3 amps
is way too high, the transformer core is probably saturating.
Primary current should be less than 1 amp.

The formula is Erms= 4.44 FNAB, where F=60, N=turns, A= cross sectional
core area in sq meters, and B= flux density, somewhere around 1 for
transformer steel.

So you should be able to figure out how many turns you need from
the size of the core. But this is a minimum figure to avoid saturating
the core, adding more turns will further reduce the current.

-Bill