Appendix C How to Select the Right AC Motor Drive|
C-2 Revision July 2008, EG03, SW V1.06
C.1 Capacity Formulas
1. When one AC motor drive operates one motor
The starting capacity should be less than 1.5x rated capacity of AC motor drive
The starting capacity=
)(______5.1
375cos973
2
kVAdrivemotorACofcapacityratedthe
t
NGD
T
Nk
A
L
×≤
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
×+
××
×
ϕη
2. When one AC motor drive operates more than one motor
2.1 The starting capacity should be less than the rated capacity of AC motor drive
Acceleration time
≦
60 seconds
The starting capacity=
()
[]
()
)(______5.11
cos
111 kVAdrivemotorACofcapacityratedthek
n
n
Pknn
Nk
sCss
T
s
T
×≤+=+
×
×
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−−
ϕη
Acceleration time
≧
60 seconds
The starting capacity=
()
[]
()
)(______1
cos
111 kVAdrivemotorACofcapacityratedthek
n
n
Pknn
Nk
sCss
T
s
T
≤+=+
×
×
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−−
ϕη
2.2 The current should be less than the rated current of 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
≤++
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
−
2.3 When 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=
)(______
cos
kVAdrivemotorACofcapacityratedthe
Pk
M
≤
×
×
ϕη
The motor capacity should be less than the capacity of AC motor drive
)(______103
3
kVAdrivemotorACofcapacityratedtheIVk MM ≤××××
−
The current should be less than the rated current of AC motor drive(A)
)(______ AdrivemotorACofcurrentratedtheIk M ≤×
