Appendix CHow to Select the Right AC Motor Drive
2.3When it is running continuously
The requirement of load capacity should be less than the capacity of AC motor drive(kVA)
The requirement of load capacity=
k ⋅ P
η⋅ cosϕ ≤ the _ capacity _ of _ AC _ motor _ drive(kVA)
The motor capacity should be less than the capacity of AC motor driveM
k ⋅ 
3 ⋅VM ⋅ IM ⋅10−3 ≤ the _ capacity_ of _ AC _ motor _ drive(kVA)
The current should be less than the rated current of AC motor drive(A)
k ⋅ IM ≤ the _ rated _ current _ of _ AC _ motor _ drive( A)
Symbol explanation
PM
η
cosϕ
VM
IM
k
PC1
kS
nT nS
GD2
TL
tA
N
:Motor shaft output for load (kW)
:Motor efficiency (normally, approx. 0.85)
:Motor power factor (normally, approx. 0.75)
:Motor rated voltage(V)
:Motor rated current(A), for commercial power
:Correction factor calculated from current distortion factor
:Continuous motor capacity (kVA)
:Starting current/rated current of motor
:Number of motors in parallel
:Number of simultaneously started motors
:Total inertia (GD2) calculated back to motor shaft (kg m2)
:Load torque
:Motor acceleration time
:Motor speed
Revision May 2008, ME14, SW V3.04 |
