Re: Watt meters

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

Original poster: dave pierson <davep-at-quik-dot-com> 

(are we getting OT?
However it IS A _TESLA_ motor...)
 >Nope.. it's a real clever electric motor.
     Yep.

 >  Consider that the torque of a motor is proportional to the armature
 >  (rotor) field multiplied by the field (stator) field.
    For that sort of motor.

>In a watt-hour meter, the stator field comes from the current in the wires


>and the rotor field comes from the voltage (potential) in the circuit

    The usual design is different.  Or at least the
    description.

    There is a conductive (usually Al) disk.
    There are two coil sets: one voltage,
    one current.

    Each induces an 'eddy current' in the disk.

    The eddy currents fields interact with the applied fields to
    produce rotation.

    The coils are displaced by 90 (physical degrees)
    so the two fields interact to create rotation.

    (Two sets of coils for single phase CT as in 99.99% of home applications)

    If the _imposed_ phases are skewed (By inductive or capacitive load)
    in addition to the physical 90 degrees from coil placement, the torque
    (hence: speed) is reduced so indication is less.

    Additionally there is a permanent magnet acting on the .Al
    disk to provide a friction free drag.

    All this is described in sundry texts...

    best
      dwp