10.3 Transformer capacity required for three-phase submersible motors
3-phase motor
[Hp]
Minimum total KVA required
*
Minimum KVA rating for each transformer
Two transformers Open Delta or Wye Three transformers Delta or Wye
1.5 3 2 1
2 4 2 1.5
3 5 3 2
5 7.5 5 3
7.5 10 7.5 5
10 15 10 5
15 20 15 7.5
20 25 15 10
25 30 20 10
30 40 25 15
40 50 30 20
50 60 35 20
60 75 40 25
75 90 50 30
100 120 65 40
125 150 85 50
150 175 100 60
200 230 130 75
*
Pump motor KVA requirements only, and does not include allowances for other loads.
10.4 Submersible drop cable selection charts (60 Hz)
The following tables indicate the recommended copper conductor
sizes and various cable lengths for submersible motors.
These tables comply with the 1978 edition of the National Electric
Table 310-16, Column 2 for +167 °F (+75 °C) wire. The ampacity
(current carrying properties of a conductor) have been divided by
1.25 per the N.E.C., Article 430-22, for motor branch circuits based
on motor amps at rated horsepower.
To ensure adequate starting torque, the maximum cable lengths are
calculated to maintain 95 % of the service entrance voltage at the
motor when the motor is running at maximum value stated on the
nameplate. Cable sizes larger than specified may always be used
and reduce power consumption.
Using cables smaller than the recommended sizes void
the warranty. Smaller cable sizes may cause reduced
starting torque and poor motor operation.
30
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