Delta Electronics VFD-DD Series - Page 137

Appendix B How to Select AC Motor Drive |DD Series
B-3
Symbol explanation
P
M
: Motor shaft output for load (kW)
η
: Motor efficiency (normally, approx. 0.85)
cos φ : Motor power factor (normally, approx. 0.75)
V
M
: Motor rated voltage(V)
I
M
: Motor rated current(A), for commercial power
k
: Correction factor calculated from current distortion factor (1.05 - 1.1, depending on PWM
method)
P
c1
: Continuous motor capacity (kVA)
k
S
: Starting current/rated current of motor
n
T
: Number of motors in parallel
n
S
: Number of simultaneously started motors
GD
2
: Total inertia (GD
2
) calculated back to motor shaft (kg m
2
)
T
L
: Load torque
t
A
: Motor acceleration time
N : Motor speed