Delta Electronics VFD-VL manual ⋅ IM ≤ the rated current of AC motor drive a

Appendix C How 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 (1.05-1.1, depending on PWM method)

: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 Nov. 2008, VLE1, SW V1.03 C-3