Grundfos SP Series Installation And Operating Instructions Manual page 25

7.6.3 Franklin motors
Refer to the Franklin submersible motors
application maintenance manual.
7.6.4 Correcting for three-phase power
imbalance
Example: Check for current unbalance for a 230
volt, three-phase, 60 Hz submersible pump
motor, 18.6 full load amps.
Solution: Steps 1 to 3 measure and record amps
on each motor drop lead for Hookups 1, 2 and 3.
Observe that Hookup 3 should be used since it
shows the least amount of current unbalance.
Therefore, the motor will operate at maximum
Step 1 (Hookup 1)
(T ) DL = 25.5 amps
1 1
(T ) DL = 23.0 amps
2 2
(T ) DL = 26.5 amps
3 3
Step 4 Total = 75 amps
Step 5 Average Current =
Greatest amp difference from
Step 6
the average:
Step 7 % Unbalance
Hookup 1
Fig. 14
efficiency and reliability.
By comparing the current values recorded on
each leg, you will note the highest value was
always on the same leg, L
unbalance is in the power source. If the high
current values were on a different leg each time
the leads were changed, the unbalance would be
caused by the motor or a poor connection.
If the current is greater than 5 %, contact your
power company for help.
*For a detailed explanation of three-phase
balance procedures, see section 4.1 Startup with
three-phase motors on p. 11.
Step 2 (Hookup 2)
DL = 25 amps
3
DL = 24 amps
1
DL = 26 amps
2
Total = 75 amps
total current =
3 readings
(Hookup 1) = 25-23 = 2
(Hookup 2) = 26-25 = 1
(Hookup 3) = 25.5-25 = .5
(HOOKUP 1) = 2/25 X 100 = 8
(HOOKUP 2) = 1/25 X 100 = 4
(HOOKUP 3) = .5/25 X 100 = 2
Hookup 2 Hookup 3
. This indicates the
3
Step 3 (Hookup 3)
DL = 25.0 amps
2
DL = 24.5 amps
3
DL = 25.5 amps
1
Total = 75 amps
75
= 25 amps
3
Subject to alterations.
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