Re: solid neutral
Most of these terms are commonly used by (and come from) the various manufacturers -- kind of common equipment slang (some of it goes way back).
This is my understanding:
Relay -- usually pilot (control) duty. The number of poles (or contacts) doesn't enter into it.
Contactor -- functions like a relay, but controls much higher amperage (power). You can get contactors rated for hundreds of amps. Sometimes you have to use a control relay interposed between a control device and a contactor, just to handle the amperage of the coil of the contactor. Contactors can be electrically held, or mechanically held. Mechanically held are more expensive, and require a pulse of control power to either close or open the contacts (they usually have an "open" coil and a "close" coil). You can get lighting contactors with a dozen poles -- the number of poles doesn't enter into it.
Starter -- basically a contactor with overloads built-in, used for controlling and protecting motors. Sometimes the contacts are heavier and easily replaced, since there is more arcing with motor loads.
Solid Neutral:
In panels it doesn't really mean much -- just that it has a neutral bar in it. Some panels used to come without a neutral bar (unless you asked for it), but today most have them included.
It is commonly used concerning disconnect switches to denote that the switch has a neutral bar and it is not switched. (as opposed to, say, a 4 pole disconnect switch with the 4th pole switching the neutral as well as the 3 phases)
In ATS it means there is a neutral bar of some type and it is not switched. (as opposed to, say, a 4 pole ATS with the 4th pole switching the neutral as well as the 3 phases)
Solid Neutral -- this generic term has been around for a long time, and it almost always means that there is a neutral bar of some kind in the equipment and that that neutral is not switched or fused or otherwise capable of being opened or interrupted (i.e. a "solid" neutral).
[ July 01, 2005, 03:00 AM: Message edited by: tx2step ]
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