[SBE] A/C 3phase vs single phase

[Robert Denny]

Chris,

Some of the smaller, inverter-type air conditioners are quite efficient, but
they are limited in cooling capacity.  Three-phase motors are smaller and
simpler in design than equivalent single-phase motors and present a more
balanced load to the source.  For a relatively small cooling load, an
inverter-type unit may be the way to go, but for large cooling loads where a
lot of shaft power is needed three-phase machines may be the only reasonable
choice.

Note that while there is two-phase power, it is hardly ever used these
days.  Commonly found today are three-phase loads and single-phase loads.
Generally, a load connected to two line (hot) wires in a domestic or
commercial system (whether or not a neutral wire is used) is single phase
load and not a two-phase load.  Three-phase loads have three hot wires and,
in the case of a Y-connected load, three hot wires and a neutral.

Regards,

Bob Denny


On 6/11/09, Chris Hoopes <hoopeschris at yahoo.com> wrote:

>

>   It comes up every now and then that I am called upon to scope out new

> air conditioning systems. I always figured with both available, that 3 phase

> was more efficient. Less current is required to start a 3 phase motor.

> Smaller gauge wires, but more of them. But then the other day I was called

> down on this. I wondered if advancement in A/C technology had changed the

> fact. The way 3 phase is measured is a difficult concept, peak demand. What

> has been your experience? Is 3 phase cheaper to operate and cool with then a

> 2 phase system? Or is there no difference?

>

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