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Appendix CHow to Select the Right AC Motor Drive|
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=
×
k
N
η
ϕ
×
×
973
cos
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
The starting capacity=
×
k
N
η
×
cos
The starting capacity=
×
k
N
[
n
T
η
ϕ
×
cos
2.2 The current should be less than the rated current of AC motor drive(A)
n
+
n
T
C-2
⎛
⎞
2
GD
N
⎜ ⎜
⎟ ⎟
+
×
≤
T
1
5 .
L
375
t
⎝
⎠
A
Acceleration time
⎡
[
]
(
)
+
=
⎢
n
n
k
P
−
s
s
1
C
1
⎢
T
ϕ
⎢
⎣
Acceleration time
⎡
]
(
)
+
=
+
⎢
n
k
P
1
−
s
s
1
C
1
⎢
n
⎢
⎣
Acceleration time
n
⎡
⎤
+
+
≤
I
1
k
1
⎛
⎞
S
−
⎜
⎟
M
⎢
S
⎥
n
T
⎝
⎠
⎣
⎦
T
Acceleration time
n
⎡
⎤
+
≤
I
1
k
1
the
⎛
⎞
S
−
⎜
⎟
M
⎢
S
⎥
n
⎝
⎠
⎣
⎦
T
×
the
_
capacity
_
of
≦
60 seconds
n
⎤
(
)
+
s
≤
×
⎥
1
k
1
5 .
the
−
s
1
⎥
n
⎥
⎦
T
≧
60 seconds
n
⎤
(
)
s
≤
⎥
k
the
_
capacity
−
s
1
⎥
⎥
⎦
T
60 seconds
≦
×
1
5 .
the
_
rated
_
≧
60 seconds
_
rated
_
current
_
AC
_
motor
_
drive
_
capacity
_
of
_
AC
_
_
of
_
AC
_
motor
current
_
of
_
AC
_
_
of
_
AC
_
motor
Revision May 2008, ME14, SW V3.04
(
kVA
)
motor
_
drive
(
kVA
)
_
drive
(
kVA
)
motor
_
drive
(
A
)
_
drive
(
A
)
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