I checked the idling current in the generated leg. Keep in mind this
is on
a newish 7.5 hp TEFC high eff motor with max load amps of 18.8 at 230
volts.

PF CAPS Gen Leg Input idle Input loaded
Idle Amps current amps current amps
0 18.1 3.9 10.3
10 18.8 4.6 8.7
20 18.1 5.6 7.8
30 18.1 6.4 7.8
40 18.4 7.1 7.1
50 18.6 8.2 6.3

As I added PF caps, my unloaded idling current went up but my loaded
current went down. In the last case, when I turned on the lathe,
the current actually dropped from 8.2 unloaded to 6.3 with load? I
imagine
this has something to do with phase angles but don't fully understand.
Adding the PF didn't change the leg to leg current or voltages much.
The leg to leg difference is still within 2 amps. From 0 to 50 mf PF
caps, the overall current magnitudes didn't change by more than 3 amps
per leg.
L1 to L3 that has 120 mf between them is still within 3 volts of L2
and L3
which has 80 mf between them. Someone questioned my readings earlier,
I checked them again and they are indeed within 2 volts of line
current. I didn't shoot for this, just stumbled on it with the 120/80
cap combination. Adding PF caps did change the voltages a bit, but
not the voltage difference between them.


"Robert Swinney" wrote in message ...
grdstat sez:

"... I tried doing this just this past weekend when I balanced out my 7.5
hp idler. Adding the PF caps didn't decrease my line current, it
increased it. ..."

Check the manufactured leg with your clamp-on ammeter with your converter
unloaded. With balancing close to optimum, you should read the motor's
name-plate current in the 3 rd. (manufactured) leg. This may sound strange!
The current you are reading is reactive. This current is out of phase with
the voltage that causes it. For example, on my 7.5 HP idler, that reading
was 22 amps which is the full load rated current of a 7.5 HP, 3-phase motor.
My mnufactured leg, or 3 rd. leg, current could more exactly be stated as:
(22 angle 30 degrees) amps, or aprox.
(19 + j11) amps.

When balanced, I had 93 uFd in one leg and 167 uFd in the other leg and 40
uFd connected between line 1 and line 2. This 40 uFd (power factor
correction) cap between input lines caused the (clamp-on) current measured
there to dip to (become a minimum) at 3.8 amps. Input line current measured
at L1 or L2 was 3.8 amps.

This from a very old, very heavy, Wagner 7.5 HP, 3-phase motor.

Bob Swinney