Appendix C How to Select the Right AC Motor Drive|
Revision July 2008, EG03, SW V1.06 C-7
5. Synchronous motor:
The rated current and starting current are higher than for standard motors. Please check
before operation and choose the capacity of the AC motor drive carefully. When the AC
motor drive operates more than one motor, please pay attention to starting and changing
the motor.
Power Transmission Mechanism
Pay attention to reduced lubrication when operating gear reduction motors, gearboxes, belts and
chains, etc. over longer periods at low speeds. At high speeds of 50/60Hz and above, lifetime
reducing noises and vibrations may occur.
Motor torque
The torque characteristics of a motor operated by an AC motor drive and commercial mains
power are different.
Below you’ll find the torque-speed characteristics of a standard motor (4-pole, 15kW):
AC motor drive Motor
180
155
140
100
80
55
38
0
320
60
120
60 seconds
Base freq.: 60Hz
V/f for 220V/60Hz
180
155
100
55
38
0
320
60
120
t
o
r
q
u
e
(
%
)
Frequency (Hz)
Frequency (Hz)
60 seconds
60 seconds
t
o
r
q
u
e
(
%
)
Base freq.: 60Hz
V/f for 220V/60Hz
130
140
100
85
45
35
0
3
20
50
120
180
150
100
45
35
0
50
120
68
80
t
o
r
q
u
e
(
%
)
t
o
r
q
u
e
(
%
)
60 seconds
60 seconds
Frequency (Hz)
Frequency (Hz)
3
20
Base freq.: 50Hz
V/f for 220V/50Hz
Base freq.: 50Hz
V/f for 220V/50Hz
