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
375
cos
973
2
kVA
drive
motor
AC
of
capacity
rated
the
t
N
GD
T
N
k
A
L
×
≤
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
×
+
×
×
×
ϕ
η
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
.
1
1
cos
1
1
1
kVA
drive
motor
AC
of
capacity
rated
the
k
n
n
P
k
n
n
N
k
s
C
s
s
T
s
T
×
≤
+
=
+
×
×
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−
−
ϕ
η
Acceleration time
≧
60 seconds
The starting capacity=
(
)
[
]
(
)
)
(
_
_
_
_
_
_
1
cos
1
1
1
kVA
drive
motor
AC
of
capacity
rated
the
k
n
n
P
k
n
n
N
k
s
C
s
s
T
s
T
≤
+
=
+
×
×
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−
−
ϕ
η
2.2 The current should be less than the rated current of AC motor drive(A)
Acceleration time
≦
60 seconds
)
(
_
_
_
_
_
_
5
.
1
1
1
A
drive
motor
AC
of
current
rated
the
k
n
n
I
n
S
M
T
S
T
×
≤
+
+
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
−
Acceleration time
≧
60 seconds
)
(
_
_
_
_
_
_
1
1
A
drive
motor
AC
of
current
rated
the
k
n
n
I
n
S
M
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
kVA
drive
motor
AC
of
capacity
rated
the
P
k
M
≤
×
×
ϕ
η
The motor capacity should be less than the capacity of AC motor drive
)
(
_
_
_
_
_
_
10
3
3
kVA
drive
motor
AC
of
capacity
rated
the
I
V
k
M
M
≤
×
×
×
×
−
The current should be less than the rated current of AC motor drive(A)
)
(
_
_
_
_
_
_
A
drive
motor
AC
of
current
rated
the
I
k
M
≤
×
Summary of Contents for AC Motor Drive VFD-G
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