[Amps] Step Start

[Colin Lamb]

George asked:

"Why do most step-start circuits in the primary of the HV transformer 
have tow resistors and relay contacts shorting the resistors in EACH 
(i.e. BOTH) leads of the primary?  

Doesn't a single resistor and relay do the same job?  It's a single 
current path."  


Response:

It would be logical to put a separate resistor in each leg of a dual primary transformer,
and have a double pole relay switch out both resistors.  Then, it would not matter
whether the primary was connected to 120 or 240.  You could not accomplish that 
with a single resistor.  I imagine it then became a case of copying the circuit,
even if the primary was not to be switched.    

Sort of like the story about the young couple that just finished Thanksgiving dinner,
with a delicious turkey.  The husband noted it was the best turkey he ever had, 
but wondered why the legs were cut off before cooking, and wondered if it had anything
to do with why it was so good.  The young wife said she did not know why the legs
were cut off, but that her mother had always done it.  They then called the mother
and she said she had always done it and the turkey always tasted great, and she 
did it because her mother had done it.  Finally, the young bride called grandma 
and asked her why the legs were cut off.  Grandma laughed and said "because
we had a small oven because her husband was a ham radio operator and bought expensive
amplifiers, but would not buy a new stove - and it would not fit in our oven unless
the legs were cut off."

Colin  K7FM