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INDUSTRIAL GENERATOR SETS — APPLICATION & INSTALLATION MANUAL — REV. #4 (09/07/07) — PAGE 23
GENSET SIZING — DETERMINING LOAD CHARACTERISTICS
Three-Phase Induction Motors
Calculate RkW as follows:
If EFF (motor running efficiency) of the motor is not known,
refer to Table 5 and use the value corresponding to the motor
horsepower.
Calculate RkVA as follows:
If RPF (running power factor) is unknown, refer to Table 5
and use the value corresponding to the motor horsepower.
Calculate SkVA as follows:
1. If the NEMA motor code letter is unknown, refer to
Table 4 on previous page and select the SkVA value
corresponding to the code letter and the horsepower.
The factors used to generate these values are shown
in Table 5.
2. If the NEMA motor code letter is unknown, refer to
Table 7 on page 25 and select the SkVA value in bold
letters that corresponds to the motor horsepower. The
bold letters show the values for the NEMA code letters
that are typical for standard motors.
3. If the motor is rated greater than 500 HP and the NEMA
motor code is known, calculate SkVA as follows:
4. If the motor is rated more than 500 HP and the NEMA
motor code is not known, assume a NEMA code letter
of G and calculate SkVA as follows:
where 5.9 is the multiplying factor corresponding to NEMA
code letter G in Table 5.
rotcaFgniylpitluMretteLedoCAMEN.5elbaT
A0.2
B3.3
C8.3
D2.4
E7.4
F3.5
G9.5
H7.6
J5.7
K5.8
L5.9
M6.01
N8.11
P2.31
R0.51
S0.61
T0.91
U2.12
V0.32
NEMA Code Letter Multiplying Factor
Use Table 5 below to calculate the starting kVA. DO NOT
confuse the NEMA (National Electrical Manufacturers
Association)
motor code
and
design letters
.
The code letter refers to the ratio of locked rotor kVA to HP,
whereas the design letter refers to the ratio of torque to speed.