Appendix C How to Select the Right AC Motor Drive|
Revision July 2008, EG03, SW V1.06 C-3
Symbol explanation
M
: Motor shaft output for load (kW)
η
: Motor efficiency (normally, approx. 0.85)
cos
: Motor power factor (normally, approx. 0.75)
MV
: Motor rated voltage(V)
M
: Motor rated current(A), for commercial power
k
: Correction factor calculated from current distortion factor (1.05 - 1.1, depending on
PWM method)
1CP
: Continuous motor capacity (kVA) P
C1
=KP
MnT
/ηcos
Sk
: Starting current/rated current of motor
Tn
: Number of motors in parallel
Sn
: Number of simultaneously started motors
2
GD
: Total inertia (GD
2
) calculated back to motor shaft (kg m
2
)
L
: Load torque
A
: Motor acceleration time
N : Motor speed
