Worksheet For Three-Phase Motors; Disposal - Grundfos CR Serie Instrucciones De Instalación Y Operación

18. Worksheet for three-phase motors

Below is a worksheet for calculating current unbalance on a three-phase hookup. Use the calculations below as a guide.
Current unbalance should not exceed 5 % at service factor load or 10 % at rated input load. If the unbalance cannot
be corrected by rolling the 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
Note
Note
from the power source. However, if the reading farthest from the averages moves with the same motor lead, the
primary source of unbalance is on the "motor side" of the starter. In this instance, consider if the cause can be a
damaged cable, an untight cable splice, a poor connection, or a faulty motor winding.
Here is an example of current readings at maximum pump loads on each leg of a three-wire hookup.
You must make calculations for all three hookups. To begin, add up all three readings for hookup numbers 1,
2, and 3.
Divide the total by three to obtain the average.
Calculate the greatest current difference from the average.
Divide this difference by the average to obtain the percentage of the unbalance.
In this case, the current unbalance for Hookup 1 is 8 %.
Hookup 1
L to T = ___ amps
1 1
L to T = ___ amps
2 2
L to T = ___ amps
3 3
TOTAL = ___ amps
Hookup 1
___ amps
3 ___ amps
Hookup 1
___ amps
___ amps
___ amps
Hookup 1
___ or ___ %
___ ___ amps

19. Disposal

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.
Explanation and examples
Blank worksheet
Hookup 2
L to T = ___ amps
1 3
L to T = ___ amps
2 1
L to T = ___ amps
3 2
TOTAL = ___ amps
Hookup 2
___ amps
3 ___ amps
Hookup 2
___ amps
___ amps
___ amps
Hookup 2
___ or ___ %
___ ___ amps
Hookup 1
T1 = 51 amps
T2 = 46 amps
T3 = 53 amps
150
TOTAL =
Hookup 1
50 amps
3 150 amps
Hookup 1
50 amps
— 46 amps
4 amps
Hookup 1
.08 or 8 %
50 4.00 amps
Hookup 3
L to T = ___ amps
1 2
L to T = ___ amps
2 3
L to T = ___ amps
3 1
TOTAL = ___ amps
Hookup 3
___ amps
3 ___ amps
Hookup 3
___ amps
___ amps
___ amps
Hookup 3
___ or ___ %
___ ___ amps
Subject to alterations.
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