Countermeasures Against Noise - Mitsubishi Electric FATEC FR-A800 Manual

7
REVIEW OF INSTALLATION ENVIRONMENT
7.2.3

Countermeasures against noise

(1) Stance of countermeasures against noise
Although there are many noise propagation paths as described in Subsection 7.2.2, the noise
source can be classified into the following three types, as shown in Fig. 7.12 and Fig. 7.13.
1) Conduction, induction, or radiation from the input power supply cable
2) Induction or radiation from the motor connection cable
3) Radiation from the inverter
Each noise level tends to be decreased as the frequency band rises. In general, it does not
matter in the frequency band of 10 MHz or more.
Therefore, it does not affect televisions or FM radios that use frequency over 70 MHz. However,
it affects low frequency band radios such as AM radios. Accordingly, it is rational to consider the
countermeasures with regard to the frequency band of the noise.
(a) Reducing the noise that leaks into the power supply cables
Inserting a filter between an inverter and the power supply cable is effective.
There are several types of filters as described below.
The following explains the usage and effect.
1) Radio noise filter FR-BIF (200 V class), FR-BIF-H (400 V class)
This filter requires distinction between 200 V and 400 V, however, it is common to all
capacities.
Connect the filter to the power supply input terminal of the inverter as shown in Fig. 7.18.
A long connection cable between the filter and inverter becomes the noise radiation
antenna which is obstructive to the effect of the filter. Therefore, connect the cables
including the earthing (grounding) cable directly to the inverter terminal so that they are as
short as possible.
In addition, when the inverter earth (ground) terminal is far from the earth, the earthing
(grounding) cable may be the antenna which is obstructive to the effect of the filter.
Therefore, the earthing (grounding) cable should also be as short as possible.
This filter has large effect on several MHz or less and is effective to decrease the noise
influence on AM radios.
Do not connect the filter to the inverter output side because it has a capacitor. Otherwise it
will be damaged.
7.2 Noise
106
Power supply
FR-BIF
Radio noise filter
Connect the connection
cable directly at the shortest
distance to the input terminal
of the inverter.
Fig. 7.18 Installation of the radio noise filter FR-BIF
R
S
Inverter
T
Earth (ground)