How to solve the electromagnetic interference generated by the use of Siemens motors and frequency converters?

Date:2020-10-27 09:47:22

I received a technical issue from a customer today.
He ordered a batch of Siemens motors and frequency converters from Chuangjuman.
 
He asked if there is any way to shield the electromagnetic interference generated by the use of motors and frequency converters from surrounding precision measuring instruments?
 
Later, I replied to him.
The recommended solution is to keep the electrical control cabinet further away from the on-site equipment and install filters. This can only reduce interference, not completely eliminate it. Some customers also use shielded motor cables to minimize interference to surrounding equipment. Either stay away from the interference source or install filtering devices.
 
In order to let more users and peers understand the issues involved, the editor of Chuangjuman has provided the following detailed answers.

Reducing the impact of the frequency converter on external devices during operation does not eliminate the external interference of the frequency converter. If you want to further improve the immunity of other devices to frequency converter harmonics and electromagnetic radiation, especially in situations where frequency converters (different brands may produce varying degrees of interference) have severe interference, commonly used methods include the following:
 
1. Use an isolation transformer
The use of isolation transformers is mainly to cope with conducted interference from the power source. By using an isolation transformer with an isolation layer, the majority of conducted interference can be blocked before the isolation transformer. At the same time, it can also have the function of converting power supply voltage. Isolation transformers are commonly used for instruments in control systems PLC， And the anti conducted interference of other low-voltage low-power electrical equipment.  
 
2. Use filtering modules or components
At present, there are many filter modules or components specifically designed for anti-interference in the market. These filters have strong anti-interference capabilities and also prevent interference from electrical appliances from being transmitted to the power supply. Some also have the function of absorbing peak voltage, which is beneficial for various types of electrical equipment. The commonly used structure is a dual hole magnetic core filter. There are also filters with single hole magnetic cores, which have weaker filtering capabilities than those with dual holes, but at a lower cost.  
 
3. Select low-voltage equipment such as instruments with switch power supplies
The anti power conduction interference ability of general switching power supplies is relatively strong, because relevant filters are also used inside the switching power supply. Therefore, when selecting power equipment for control systems or electrical appliances, it is advisable to use switch mode power supplies.  
 
4. Ensure anti-interference of signal lines
The signal line undertakes the transmission tasks of detecting and controlling signals. Undoubtedly, the quality of signal transmission directly affects the accuracy, stability, and reliability of the entire control system. Therefore, it is necessary to do a good job in anti-interference of the signal line.  
 
The distribution parameters of interference are very complex, so appropriate measures should be taken in anti-interference, considering both the effect and price factors, as well as the on-site situation.
 
As long as the measures adopted can solve the problem, excessive anti-interference measures may generate additional interference, and specific solutions should be taken according to the specific situation.