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32.
TRANSFORMER SIZES
A full three phase supply is recommended for all three phase motors, consisting of three phase individual transformers
or one three phase transformer.
"Open" delta or wye connections using only two transformers can be used, but are more likely to cause problems from
current unbalance.
Transformer ratings should be no smaller than listed in the table for supply power to the motor alone.
Table 20: TRANSFORMER SIZING
HP
kW
1.5
2
3
5
7.5
10
33.
POWER SUPPLY BY A GENERATOR
Attention: the applicable tolerances from main supply must also be applied by power supply via generators
When operating a motor via a generator please bear in mind that the starting current of the motor is five times the
nominal motor current and that mean power factor of 0.6 for starting can be expected.
Also make sure that a sufficient generator power is permanently available and that for
starting the voltage must be at least 65% of the nominal motor Name plate voltage.
Required kVa
1.1
3.0
1,5
4.0
2.2
5.0
3.7
7.5
5.5
10
7.5
15
4MWP
4" Submersible Motors
KVA Rating (smallest) For Each Transformer
Open WYE or D 2
Transformers
2.0
2.0
3.0
5.0
7.5
10.0
Closed WYE or D 3
Transformers
1.0
1.5
2.0
3.0
5.0
5.0
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