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Dynamic Braking Section 5-3
5-2-3 Zero-phase Reactor (RF Noise Filter)
The zero-phase reactor helps reduce radi-
ated noise from the inverter wiring. It can
be used on the input or output side of the
inverter. The example zero-phase reactor
shown to the right comes with a mounting
bracket. The wiring must go through the
opening to reduce the RF component of
the electrical noise. Loop the wires three
times (four turns) to attain the full RF filter-
ing effect. For larger wire sizes, place multi-
ple zero-phase reactors (up to four) side-
by-side for a greater filtering effect.
5-2-4 EMI Filter
The EMI filter reduces the conducted noise on the power supply wiring gener-
ated by the inverter. Connect the EMI filter to the inverter primary (input side).
Filter is required for compliance to the EMC Class A directive (Europe) and C-
TICK (Australia). See D-1 CE-EMC Installation Guidelines on page 327.
!WARNING The EMI filter has high internal leakage current from power wiring to the chas-
sis. Therefore, connect the chassis ground of the EMI filter before making the
power connections to avoid danger of shock or injury.
5-2-5 DC Link Choke
The DC choke (reactor) suppresses harmonics generated by the inverter. It
attenuates the high-frequency components on the inverter's internal DC bus
(link). However, note that it does not protect the diode rectifiers in the inverter
input circuit.
5-3 Dynamic Braking
5-3-1 Introduction
• The purpose of dynamic braking is to improve the ability of the inverter to
stop (decelerate) the motor and load. This becomes necessary when an
application has some or all of the following characteristics:
• High load inertia compared to the available motor torque
• The application requires frequent or sudden changes in speed
• System losses are not great enough to slow the motor as needed
When the inverter reduces its output frequency to decelerate the load, the
motor can temporarily become a generator. This occurs when the motor rota-
tion frequency is higher than the inverter output frequency. This condition can
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