Delta VFD-EL-W Series - Capacity Formulas

Appendix C. How to Select the Right AC Motor Drive｜VFD-EL-W
207
C-1 Capacity Formulas
1. One AC motor drive operates one motor
The starting capacity should be less than 1.5x the rated capacity of the AC motor drive.
The starting capacity equals:
)(_____5.1
375cos973
2
kVAdrivemotorACofcapacitythe
t
NGD
T
Nk
A
L













2. One AC motor drive operates more than one motor
 The starting capacity should be less than the rated capacity of the AC motor drive.
Acceleration time ≤ 60 seconds
The starting capacity equals:
 
 
 
)(_____5.11
cos
111 kVAdrivemotorACofcapacitythek
n
n
Pknn
Nk
sCss
T
s
T 














Acceleration time ≥ 60 seconds
The starting capacity equals:
 The current should be less than the rated current of the AC motor drive (A).
Acceleration time ≤ 60 seconds
)(______5.111 AdrivemotorACofcurrentratedthek
n
n
In SM
T
S
T 













Acceleration time ≥ 60 seconds
)(______11 AdrivemotorACofcurrentratedthek
n
n
In SM
T
S
T 













 When running continuously
The load capacity requirement should be less than the capacity of the AC motor drive (kVA).
The load capacity requirement equals:
)(_____
cos
kVAdrivemotorACofcapacitythe
Pk M




The motor capacity should be less than the capacity of the AC motor drive.
)(_____103
3
kVAdrivemotorACofcapacitytheIVk MM 

The current should be less than the rated current of the AC motor drive (A).
)(______ AdrivemotorACofcurrentratedtheIk M 
 
 
 
)(_____1
cos
111 kVAdrivemotorACofcapacitythek
n
n
Pknn
Nk
sCss
T
s
T 













