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9
Basic System Description
A motor control system will obviously include a motor and inverter, as well as a circuit
breaker or fuses for safety. If you are connecting a motor to the inverter on a test bench
just to get started, that’s all you may need for now. But a system can also have a variety of
additional components. Some can be for noise suppression, while others may enhance the
inverter’s braking performance. The figure and table below show a system with all the
optional components you might need in your finished application.
Name Function
Breaker /
disconnect
A molded-case circuit breaker (MCCB), ground fault
interrupter (GFI), or a fused disconnect device. NOTE: The
installer must refer to the NEC and local codes to ensure
safety and compliance.
Input-side
AC Reactor
This is useful in suppressing harmonics induced on the
power supply lines and for improving the power factor.
WARNING: Some applications must use an input-side AC
Reactor to prevent inverter damage. See Warning on next
page.
Radio noise filter
Electrical noise interference may occur on nearby
equipment such as a radio receiver. This magnetic choke
filter helps reduce radiated noise (can also be used on
output).
EMC filter (for
CE applications,
see Appendix D)
Reduces the conducted noise on the power supply wiring
between the inverter and the power distribution system.
Connect to the inverter primary (input) side.
Radio noise filter
(use in non-CE
applications)
This capacitive filter reduces radiated noise from the main
power wires in the inverter input side.
DC link choke
Suppress harmonics generated by the inverter. However, it
will not protect the input diode bridge rectifier.
Radio noise filter
Electrical noise interference may occur on nearby
equipment such as a radio receiver. This magnetic choke
filter helps reduce radiated noise (can also be used on
input).
Output-side
AC Reactor
This reactor reduces the vibration in the motor caused by
the inverter’s switching waveforms, by smoothing the
waveform to approximate commercial power quality. It is
also useful to reduce harmonics when wiring from the
inverter to the motor is more than 10m in length.
LCR filter
Sine wave shaping filter for output side.
Breaker,
MCCB or
GFI
From power supply
M
Thermal
switch
L1 L2 L3
T1 T2 T3
Inverter
+1
+
GND