Grundfos SP 1100S, Installation And Operating Instructions Manual

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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 V, 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 operates at
maximum efficiency and reliability.
By comparing the current values recorded on each leg, it can be
noted that the highest value is always on the same leg, L
3
. This
indicates the imbalance is in the power source. If the high current
values are on a different leg each time the leads are changed, the
imbalance would be caused by the motor or a poor connection.
If the current imbalance is greater than 5 %, contact the power
supply company for.
For a detailed explanation of three-phase balance procedures, see
section Check for 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
L3 L2 L2 L1 L1 L1 L3 L2 L3 L2
L3 L2 L1
T3 T2 T1
DL3 DL2 DL1
M1 M3
M2
L3 L2 L1
T3 T2 T1
DL2 DL1 DL3
M1 M3
M2
L3 L2 L1
T3 T2 T1
DL1 DL3 DL2
M1 M3
M2
1 2 3
4
5
6
7
8
TM050042
Correcting for three-phase current imbalance
Pos. Description
1 Hookup 1
2 Hookup 2
3 Hookup 3
4 Fused disconnect switch
5 Magnetic starter
6
Manual reset of thermal overload with extra quick trip
heaters
7 Submersible drop cable
8 Motor
Related information
7.1.2 Check for current imbalance
11. Disposing of the product
This product or parts of it must be disposed of in an environmentally
sound way.
1. Use the public or private waste collection service.
2. If this is not possible, contact the nearest Grundfos company or
service workshop.
The crossed-out wheelie bin symbol on
a product means that it must be
disposed of separately from household
waste. When a product marked with
this symbol reaches its end of life, take
it to a collection point designated by
the local waste disposal authorities.
The separate collection and recycling
of such products will help protect the
environment and human health.
See also end-of-life information at www.grundfos.com/product-
recycling .
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