Grundfos SP User Manual

43
English (US)
10.6.2 Other motor manufacturers
Refer to the other motor manufacturers'
application maintenance manual.
10.6.3 Correcting for three-phase current
imbalance
Example: Check for current imbalance for a 230
volt, three-phase, 60 Hz submersible motor,
18.6 full load amps.
Solution: Steps 1 to 3 measure and record
amps on each submersible drop cable lead for
hookups 1, 2 and 3.
Observe that hookup 3 must be used since it
shows the least amount of current imbalance.
Therefore, the motor will operate at maximum
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
3
. This indicates the
imbalance is in the power source. If the high
current values were on a different leg each time
the leads were changed, the imbalance would
be caused by the motor or a poor connection.
If the current imbalance is greater than 5 %,
contact your power supply company for help.
For a detailed explanation of three-phase
balance procedures, see section 7.1 Startup
with three-phase motors.
Fig. 18 Correcting for three-phase current imbalance
Step 1 (hookup 1) Step 2 (hookup 2) Step 3 (hookup 3)
(T
1
) DL
1
= 25.5 amps DL
3
= 25 amps DL
2
= 25.0 amps
(T
2
) DL
2
= 23.0 amps DL
1
= 24 amps DL
3
= 24.5 amps
(T
3
) DL
3
= 26.5 amps DL
2
= 26 amps DL
1
= 25.5 amps
Step 4 Total = 75 amps Total = 75 amps Total = 75 amps
Step 5 Average current =
total current
=
75
= 25 amps
3 readings 3
Step 6
Greatest amp difference
from the average:
(hookup 1) = 25 - 23 = 2
(hookup 2) = 26 - 25 = 1
(hookup 3) = 25.5 - 25 = 0.5
Step 7 % imbalance
(hookup 1) = 2/25 x 100 = 8
(hookup 2) = 1/25 x 100 = 4
(hookup 3) = 0.5/25 x 100 = 2
TM05 0042 2413
L
3
L
2
L
2
L
1
L
1
L
1
L
3
L
2
L
3
L
2
L
3
L
2
L
1
T
3
T
2
T
1
DL
3
DL
2
DL
1
M
1
M
3
M
2
L
3
L
2
L
1
T
3
T
2
T
1
DL
2
DL
1
DL
3
M
1
M
3
M
2
L
3
L
2
L
1
T
3
T
2
T
1
DL
1
DL
3
DL
2
M
1
M
3
M
2
Hookup 1 Hookup 2 Hookup 3
Fused
disconnect
switch
Magnetic starter
Manual reset of thermal overload
with extra quick trip heaters
Submersible drop cable
Motor

Grundfos SP Specifications

General

Material	Stainless Steel
Pump Type	Submersible
Application	Irrigation
Motor Range	0.37 kW to 4 kW
Liquid Temperature	0 °C to 40 °C
Series	SP
Power Range	0.37 kW to 4 kW
Frequency	50 Hz, 60 Hz
Head	Up to 200 m
Discharge Size	1 inch to 4 inches