Overview of several issues related to Inverter interference (III)
3. Shielding interference Source: shielding interference source is a very effective method to suppress interference.
Usually, the frequency converter itself is shielded with an iron shell to prevent its electromagnetic interference from leaking, but the output line of the frequency converter is best shielded with steel pipes, especially with external signals (Output 4 ~ from the controller ~ 20mA signal)
When controlling the frequency converter, the control signal line is required to be as short as possible (Generally within 20 m)
, And must use shielded twisted pair, and with the main circuit line (AC380)And control lines (AC220V)Completely separated.
In addition, the electronic sensitive equipment lines in the system also require shielded twisted pairs, especially pressure signals.
And all signal lines in the system must not be placed in the same piping or trunking as the main circuit line and control line.
In order to make the shielding effective, the shielding layer must be reliably grounded.
4. Reasonable wiring: the specific methods are :(1)
Equipment of power line and signal line should be as far as possible from the frequency converter of input and output lines. (2)
The power lines and signal lines of other equipment should avoid being parallel to the input and output lines of the frequency converter.
If the above measures still do not work, then continue the following methods: 5. Interference isolation: the so-called interference isolation, it refers to the isolation of interference sources and vulnerable parts from the circuit so that they do not have electrical contact.
Usually, isolation transformers are used on the power line between the power supply and amplifier circuits such as controllers and transmitters to avoid conduction interference. Noise isolation transformers can be used for power isolation transformers.
6. Set the filter in the system circuit: the function of the equipment filter is to suppress the interference signal from the inverter to the power supply and the motor through the power line.
In order to reduce electromagnetic noise and loss, an output filter can be set on the output side of the inverter;
In order to reduce the interference to the power supply, the input filter can be set on the input side of the frequency converter.