LC programmable logic controllers (PLCs) are widely used in various fields. Because they consist of numerous electronic components, they are highly susceptible to interference from surrounding electrical components, strong magnetic and electric fields, ambient temperature and humidity, and large vibrations, which can affect their normal operation. This is often overlooked. Even with excellent programming, neglecting proper installation can lead to numerous malfunctions during later debugging and operation, resulting in arduous maintenance. The following are installation precautions:
1. PLC Installation Environment: a) Ambient temperature: 0~55 degrees Celsius. Temperatures that are too high or too low can cause internal electrical components to malfunction. Take cooling or heating measures if necessary. b) Ambient humidity: 35%~85%. Excessive humidity can increase the conductivity of electronic components, easily reducing their withstand voltage and causing excessive current and breakdown. c) Do not install PLCs with a vibration frequency above 50Hz or amplitude above a certain value, as excessive vibration can cause internal circuit board electronic components to desolder or detach. d) Keep PLCs as far away as possible from strong magnetic fields and electric fields (such as control transformers, large-capacity AC direct contactors, large-capacity capacitors, etc.) and control devices that easily generate high-order harmonics (such as frequency converters, servo drives, inverters, thyristors, etc.). e) Avoid installation in locations with high levels of metal dust, corrosion, flammable gases, or humidity. f) Inside the electrical box, it is best to place PLCs on the upper part, away from heat sources. Consider cooling and external ventilation if necessary. 2. Power Supply: a) Ensure correct connection to the PLC power supply, which can be AC or DC. Siemens PLCs offer DC 24V; AC PLCs offer more flexible input voltage, ranging from 100V to 240V (allowable range 85V to 264V), with a frequency of 50/60Hz, eliminating the need for a switch. It is best to use an isolation transformer to supply power to the PLC. b) The PLC's DC 24V output is generally used for powering expansion modules, external three-wire sensors, or other purposes. Although the DC 24V output has overload and short-circuit protection and limited capacity, it is recommended to use a separate switching power supply for external three-wire sensors to prevent short circuits that could damage the PLC and cause unnecessary problems. 3. Wiring and Routing: When wiring, use cold-pressing plates to crimp the connections before connecting them to the PLC's input/output terminals. Securely fasten the connections. When the input is a DC signal, if there are many sources of interference, consider using shielded cables or twisted-pair cables. Avoid routing the cables parallel to power lines and do not place them in the same cable trays or conduits to prevent interference. 4. Effective grounding can prevent surge signal interference. The grounding resistance should not exceed 100 ohms. If there is a grounding copper busbar in the electrical box, it should be directly connected to the grounding busbar. It should not be connected to the grounding of other controllers (such as frequency converters) before being connected to the grounding busbar. 5. Other: a. PLCs should not be installed vertically or horizontally. If the PLC is a fixed type, the screws should be tightened during installation to prevent vibration and damage to internal electronic components. If it is a rail-mounted type, a qualified rail must be selected. First, pull open the latch, then insert it into the rail, and then push the latch in. After locking, the PLC controller cannot move up, down, left, or right. b. If it is a relay output type, its output point current capacity is 2A. Therefore, when driving a large load (such as a DC clutch or solenoid valve), even if the current is less than 2A, it is better to consider using a relay for transition.
Technical specifications of rapid temperature change test chamber:
