Xylem Wastewater (Technical Manual) - Manual (Page 12)

PAGE 12
Wastewater
Goulds Water Technology, Bell & Gossett,
Red Jacket Water Products, CentriPro
Hookup 1 Hookup 2 Hookup 3
L1 L2 L3 L1 L2 L3 L1 L2 L3
Starter
Terminals
T1 T2 T3 T1 T2 T3 T1 T2 T3
Motor
Leads R B W W R B B W R
T3 T1 T2 T2 T3 T1 T1 T2 T3
Example:
T3-R = 51 amps T2-W = 50 amps T1-B = 50 amps
T1-B = 46 amps T3-R = 48 amps T2-W = 49 amps
T2-W = 53 amps T1-B = 52 amps T3-R = 51 amps
Total = 150 amps Total = 150 amps Total = 150 amps
÷ 3 = 50 amps ÷ 3 = 50 amps ÷ 3 = 50 amps
— 46 = 4 amps — 48 = 2 amps — 49 = 1 amps
4 ÷ 50 = .08 or 8% 2 ÷ 50 = .04 or 4% 1 ÷ 50 = .02 or 2%
THREE PHASE POWER UNBALANCE
A full three phase supply is recommended for all three phase
motors, consisting of three individual transformers or one three
phase transformer. So-called “open” delta or wye connections
using only two transformers can be used, but are more likely to
cause problems, such as poor performance overload tripping or
early motor failure due to current unbalance.
Transformer ratings should be no smaller than listed in Table 2
on page 3 for supply power to the motor alone.
Checking and correcting rotation and current unbalance
1. Establish correct motor rotation by running in both directions.
Change rotation by exchanging any two of the three motor
leads. The rotation that gives the most water flow is always
the correct rotation.
2. After correct rotation has been established, check the current
in each of the three motor leads and calculate the current
unbalance as explained in 3 below.
If the current unbalance is 2% or less, leave the leads as con-
nected.
If the current unbalance is more than 2%, current readings
should be checked on each leg using each of the three pos-
sible hook-ups. Roll the motor leads across the starter in the
same direction to prevent motor reversal.
3. To calculate percent of current unbalance:
A. Add the three line amp values together.
B. Divide the sum by three, yielding average current.
C. Pick the amp value which is furthest from the average cur-
rent (either high or low).
D. Determine the difference between this amp value (furthest
from average) and the average.
E. Divide the difference by the average.
Multiply the result by 100 to determine percent of
unbalance.
4. Current unbalance should not exceed 5% at service factor load
or 10% at rated input load. If the unbalance cannot be cor-
rected by rolling leads, the source of the unbalance must be
located and corrected. If, on the three possible hookups, the
leg farthest from the average stays on the same power lead,
most of the unbalance is coming from the power source. How-
ever, if the reading farthest from average moves with the same
motor lead, the primary source of unbalance is on the “motor
side” of the starter. In this instance, consider a damaged cable,
leaking splice, poor connection, or faulty motor winding.
Phase designation of leads for CCW rotation viewing
shaft end
To reverse rotation, interchange any two leads.
Phase 1 or “A” – Black Motor Lead or T1
Phase 2 or “B” – White Motor Lead or T2
Phase 3 or “C” – Red Motor Lead or T3
Notice: Phase 1, 2 and 3 may not be L1, L2 and L3.
FIGURE 12
OPEN DELTA
FULL THREE
PHASE
Application – Three Phase Unbalance