How can air finned heaters suppress interference from peripheral equipment?
(1) Protection of PLC input and output terminals
In order to avoid the higher induction potential generated when the inductive input or output circuit is disconnected, it has a greater impact on the PLC, and the drive element of the PLC is mainly composed of a solenoid valve and an AC contactor coil. The use of zero-crossing solid-state relay AC-SSR in the middle is an effective solution.
(2) Error prevention of input and output signals
In order to reduce the PLC input current and the current on the external load, a parallel bypass resistor is generally used at the input and output ends.
(3) Leakage current
When using DC two-wire sensor input signals such as proximity switches and photoelectric switches, if the leakage current is large, the resulting malfunctions should be considered so that the PLC input signal cannot be turned off. At this time, a bypass resistor can be connected to the PLC input terminal to reduce the input impedance. Similarly, when the bidirectional thyristor is used as the output, in order to avoid leakage current and other reasons caused by the output component can not be turned off, a bypass resistor can also be connected in parallel at the output end.
(4) Surge voltage
When the controller is a contact output, regardless of whether the controller itself can resist interference, adopt RC absorption for AC loads, and use a freewheeling diode for DC loads to absorb the surge voltage generated by inductive loads.
(5) Inrush current
Transistor or bidirectional thyristor output module is used to drive incandescent lamp or other loads with large power supply. It is necessary to connect the bypass output of the PLC output or connect the load in series to limit the current of the resistor to protect the output module.
Air finned heaters suppress power supply interference. Under normal circumstances, the power supply of the PLC system and the power supply system of the power supply system are separated, and a shielded isolation transformer is added between the PLC system. Use a twisted pair greater than or equal to 2m2 between the secondary side of the isolation transformer and the PLC system. Place the shield between the two coils on the primary and secondary sides and connect them to the ground, which can effectively avoid direct coupling between the coils. For eliminating power harmonics, you can use a filter before isolating the regulator.
