A step start circuit is used for one thing, and that is to reduce the surge
current when a transformer is first fired up (being magnetized). This current
can be several times the operating or magnetizing current, and can last up to
+/- 1/2 second. For amps that use a C-core (cut core) type transformer, a step
start shouldn't be needed at all. I have seen some manufacturers use them
though. By tests done by William McLyman at JPL, a gapped C-core does not have
such surge current as compared to a transformer without gaps (IE interleaved
construction or solid wound toroids). Interleaved construction does have the
surge current phenomenon as mentioned earlier. The trade offs are that a C-core
transformer has a larger magnetizing current (current at idle) than an
interleaved transformer. This is due in part to the C-core having a lower
permeability than an interleaved or solid wound core plus other losses. In
other words, you'll fill the effects of a C-core in your wallet over the
power bill. However, there was some tests done on what is known as a
composite core. These can be made in the C-core or interleaved designs. The
composite type meaning that 1/2 of the core is solid or interleaved, and the
other 1/2 is gapped or butt stacked. This, from tests at JPL, showed that you
get the best of both worlds. Both being reduced surge current, and reduced
magnetizing current. They used composite cores mainly in some impedance
transformers, but now are coming into the power transformer business. If one
wanted, they could order this type of transformer and specify the core be a
composite. I will stress this though, a C-core composite will be very much
higher in price than an EI core which can be stacked. This is due to the fact
that the C-cores matching solid core has to be wound similar to a solid toroid
by special time consuming machines. Since the EI composite should act the same
as the C-core composite, then the EI would be the best bet as it would be way
cheaper. The weight will go up some, but it's not as much as one would think.
Information about this type of composite core, including the tests can be found
in the book titled; Transformer and Inductor Design Handbook 2nd edition, by
Col. William T. McLyman. The ISBN number is; 0-8247-7828-6.
I said I would not comment on the wiring debacle but one thing to mention. The
neutral (white wire), and the ground (either naked or green) go to the same set
of ground terminals (IE ground terminal strip) in the breaker box. Also, an
electron is color blind.
Best,
Will
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