ABB UAD149A0001 3BHE014135R0001 Electronic equipment electromagnetic compatibility

ABB UAD149A0001 3BHE014135R0001 Grounding is one of the effective means of improving the electromagnetic compatibility (EMC) of electronic equipment. Correct grounding can suppress both the effects of electromagnetic interference and the equipment to send out interference; while the wrong grounding, on the contrary, will introduce serious interference signals, so that the PLC system will not work properly.

ABB UAD149A0001 3BHE014135R0001 The ground of the control system includes the system ground, shielded ground, AC ground and protective ground. Grounding system confusion on the PLC system interference is mainly uneven distribution of the potential of each grounding point, there is a ground potential difference between different grounding points, resulting in ground loop current, affecting the normal operation of the system. For example, the cable shield must be grounded at one point, if the cable shield ends A, B are grounded, there is a ground potential difference, there is a current flowing through the shield, when anomalies such as lightning strikes, the ground current will be greater.

ABB UAD149A0001 3BHE014135R0001 of the shield, ground wire and earth may constitute a closed loop, under the action of the changing magnetic field, there will be induced currents in the shield, through the shield and the coupling between the core wire to interfere with the signal loop. If the system ground and other ground processing chaos, the resulting ground loop may produce unequal potential distribution in the ground, affecting the normal operation of logic circuits and analog circuits within the PLC. PLC work logic voltage interference tolerance is low, the logic of the distribution of ground potential interference is likely to affect the PLC’s logic operations and data storage, resulting in data confusion, program run or crash. Analog ground potential distribution will lead to a decline in measurement accuracy, causing serious distortion of the signal measurement and control and false action.