The engineers in sci.engr.electrical.sys-protection were useless on
this question, so I thought I would ask it here where the *real*
The question is regarding the use of 3-phase power. I noticed an
electric pottery kiln the other day that used 3-phase power. It was
about a 6 or 7 kw model. As I understand it, electric kilns are
resistance loads, just like a toaster oven.
I had always thought that 3-phase power was an advantage only for
induction loads, and had no advantage over single-phase for resistance
loads. Is that correct? If so, what would the advantage be for a
3-phase kiln such as those shown at
Thanks for any enlightenment.
The advantage is lighter gauge supply wire and smaller control
contactors since you are dividing the load across three wires instead of
two with the resulting lower current per wire. You also balance the load
across all three power phases in the building as opposed to
concentrating the load on only two phases. No other particular
The advantages Pet mentions are relatively minor in a smallish kiln like
The other advantage is much simpler to understand: "because it interfaces
with 3 phase power".
Kilns like this are most often situated in light industrial or commercial
buildings. Such buildings are usually fed with three phase. Aside
from general purpose outlet circuits (and _some_ lighting), the higher
power circuits (ones you'd sling 30A at 240V devices on) are virtually
all 3 phase (or 2 phase of 3) devices.
Which is why, for example, in large commercial wood working shops, even
the smaller tools (eg: a 14" bandsaw with a 1HP motor, which'd
normally be on a 15A 120V circuit in a home hobbyist's house) are
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
Looking at the web page you linked to it is obvious to
me that the 3-phase kilns are special purpose. They
clearly state that they are special order only. I
assume they are for use where you only have 3-phase
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