Re: Input power measurement

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Paul Nicholson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

John,

 > The electrical current triangle consists of the Active
 > (Incan Lamp), Total (Std Ammeter), and Reactive (Calcs) currents.

Unfortunately, the lamp power is proportional to the square of the
total current, not the square of the real (aka active) current.

It is registering the 'active' power alright - but the active power
in the lamp, not in the circuit as a whole.  The active power in
the lamp is (total_current)^2 times the lamp resistance.

The lamp is aware of only the line (total) current and its own
voltage drop, and not the line voltage.

As gary says, there's no way to register the effect of the phase
angle between circuit current and load voltage using a lamp.

--
Paul Nicholson
--