Flint & Walling Commander Pro 300 - Manual (Page 11)

11
95 North Oak Street • Kendallville, IN 46755
1. Disconnect all three drop cables from the control
box. For temporary identification, tie a numbered
tag to each cable (1, 2, 3).
2. Using an ohmmeter, check the resistance
between cables as follows:
Unknown Value Known Value
Cable 1 to Cable 2
Cable 1 to Cable 3
Cable 2 to Cable 3
Lowest - Black to Yellow
Intermed. - Red to Yellow
Highest - Black to Red
NOTE: The “yellow” cable is that giving lowest and
intermediate readings and the “red” cables gives
highest and intermediate readings.
Example:
• 1 to 2 gives 7 ohms (highest reading)
• 1 to 3 gives 5 ohms (intermediate reading)
• 2 to 3 gives 2 ohms (lowest reading)
• Cable 3 gave both intermediate and lowest
reading
• Cable 3 is the yellow cable
• Cable 1 gave both highest and intermediate
readings
• Cable 1 is the red cable
• Cable 2 is the black cable
The actual ohm values are not important. The
method works regardless of the actual ohm readings;
what matters is which reading is highest, which
intermediate, and which lowest.
THREE PHASE POWER UNBALANCE
1. 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 from current unbalance.
Transformer Capacity Required for
Submersible Motors
Motor
HP
Total
Effective
KVA
Required
Smallest KVA Rating — Each
Transformer
Open WYE or
DELTA
2 Transformers
Closed WYE or
DELTA
3 Transformers
1-1/2
2
3
5
7-1/2
10
15
20
25
30
40
50
60
75
100
3
4
5
7.5
10
15
20
25
30
40
50
60
75
90
120
2
2
3
5
7.5
10
15
15
20
25
30
35
40
50
65
1
1.5
2
3
5
5
7.5
10
10
15
20
20
25
30
40
2. Transformer ratings should be no smaller than
listed in the table for supply power to the motor
alone. Open Wye or Delta systems often
suffer from line unbalance, which can cause
poor motor performance, nuisance overload
tripping, or premature motor failure. For the
best performance current unbalance should not
exceed 5 percent. If the unbalance cannot be
corrected by rolling leads, contact the power
company.
INSULATION RESISTANCE
Unbalance Formula
Percent
Current = Max difference from average x 100
Unbalance average
Example:
Currents are 80, 79, 84 amps (Lines 1-2 & 3)
Avg. Currents = 80 + 79 + 84 = 81
3
Percent
Current
Unbalance
84 - 81 x 100 = 3.7%
81
IL0104
Figure 13
Open Delta
Full Three Phase
Insulation resistance tests indicate the value of the
motor, cable, and splice insulation system by
measuring resistance in ohms between motor leads
and ground. Low readings indicate a breakdown
somewhere in the insulation system.
1. Set ohmmeter to RX100K or highest scale. (For
best results use a megohmmeter).
2. Short meter leads together and adjust indicator to
zero.
3. Be sure power is turned off!
4. Connect one meter lead to a motor lead and the
other meter lead to ground.
a. If motor is out of water, measure from lead to
motor frame.
b. If motor is installed in water, ground reference
should be metal well casing (if submerged),