Xylem GSSERVICE R2 Service Manual Submersible Pumps & Jet Pumps - Manual (Page 91)

THREE PHASE UNBALANCE
89
Calculate percentage of current unbalance for
all three hookups.
Example:
Hook Up 1 Hook Up 2 Hook Up 3
T1= 51 Amps T3 = 50 Amps T2 = 50 Amps
T2 = 46 Amps T1= 48 Amps T3 = 49 Amps
T3 = 53 Amps T2 = 52 Amps T1= 51 Amps
Add up all three readings for hook up number 1.
T1 = 51 Amps
T2 = 46 Amps
+T3 = 53 Amps
Total 150 Amps
Divide the total by three to obtain the average.
50 Amps = Average
3 150 Amps
Calculate the greatest amp difference from the aver-
age. Could be greater than average.
50 Amps
-46 Amps
4 Amps
Divide this difference by the average to obtain the
percentage of unbalance.
.08 or 8%
50 4.00 Amps
Hook Up #1 = 8%
Hook Up #2 = 4%
Hook Up #3 = 2%
Always use hook up with lowest % current unbalance.
Loads on a transformer bank vary. Readings should be
taken at peak load period.
What It Means –
1. Hook ups below 5% = system balanced.
2. Hook ups not below 5% – if the unbalance moves with
the motor leads the unbalance is caused by the motor,
wet splice, or damaged cable. Check the motor on
pages 44-45. If the unbalance remains with the termi-
nals the unbalance is in the power supply – contact
power company.