| RF Dude 2006-01-24, 7:21 pm |
| Thats very interesting and I'm glad you pointed out the measurement error
with a 2 phase unbalanced load. So what would be the solution for measuring
the 2 phase (120 degree) neutral imbalance correctly? A three phase meter
would be one answer, or could the newest ELECTRONIC single phase meters
react correctly?
I ask this cause it isn't that uncommon to have certain "2 phase" tenant
loads using single phase 120/240V load panels in a commercial 3 phase
building. Telecom and cellular tenants come to mind. The check meter to pay
the landlord back is usually single phase, which in your explaination would
short change the landlord.
RF Dude
"Solar Flare" <sfl@hutmail.notvalid> wrote in message
> Where a 3 wire single phase service is converted to a
> two phase 120 degree potential service (3ph 4w one leg
> missing) then phase to neutral unbalance (120 volt)
> loads will not be measured correctly. The phase to
> phase pot coil in the single phase meter will measure
> 1/2 the voltage x the neutral current.
>
> e.g.. With a single 120 volt @ 10 ampere load = 1200
> Watts = 1200 VAs
> the meter would see 208 volts x 1/2 of 10 amperes
> = 1040 VAs x cos(30 deg)= 901 Watts
> = 25% low (unfair to the utility)
> This only works for the unbalanced load on the service.
> For balanced and phase to phase (240 volt) loads all is
> measured correctly.
|