Ensuring the electromagnetic compatibility (EMC) of elevator dedicated power supply UPS fan power supplies requires a two-pronged approach: suppressing electromagnetic interference and enhancing anti-interference capabilities. A systematic design is needed to ensure stable operation in complex electromagnetic environments. EMC comprises two core requirements: the electromagnetic interference (EMI) generated by the equipment itself must be controlled within standard limits, and it must also possess the ability to resist external electromagnetic interference (EMS). For elevator dedicated power supply UPS fan power supplies, the operating environment may contain interference sources such as frequency converters, motor start/stop, and wireless communication equipment. If not effectively addressed, this can lead to abnormal fan speed, UPS output fluctuations, or even system shutdown, threatening elevator safety.
Suppressing electromagnetic interference requires a collaborative design approach addressing the source, propagation path, and endpoint. The main interference sources for elevator dedicated power supply UPS fan power supplies include switching circuits, rectifier circuits, and high-frequency transformers. In the switching circuit, the loop formed by the switching transistor and the high-frequency transformer generates rapidly changing currents, causing conducted and radiated interference. Optimizing the design parameters of transformers and inductors, such as using low-loss magnetic cores and properly winding coils, can reduce magnetic field leakage. Simultaneously, the PCB layout of high-frequency current loops should follow the principles of "short, thick, and straight" to reduce loop area and suppress radiated emissions. In rectifier circuits, the reverse recovery process of diodes generates high-frequency current spikes, which can be smoothed by adding buffer circuits (such as RC snubber circuits) or selecting soft-recovery diodes. High-frequency transformers require shielding layer design (such as copper foil shielding) to block electromagnetic coupling between the primary and secondary windings, reducing common-mode interference.
Blocking propagation paths requires a combination of shielding and filtering techniques. The metal casing of the elevator dedicated power supply UPS fan power supply should be sealed, with conductive gaskets or spring sheets at each joint to achieve electrical continuity, forming a Faraday cage effect and shielding against external radiated interference. For power lines and signal lines that must penetrate the casing, high-frequency magnetic rings or feedthrough capacitors should be added to suppress common-mode interference; simultaneously, EMI filters should be added at the input and output terminals, using inductors (chokes) to suppress differential-mode interference and capacitors (X capacitors, Y capacitors) to suppress common-mode interference. The filter should be installed close to the power interface to avoid introducing parasitic parameters due to excessively long leads, which would reduce the filtering effect.
Enhancing anti-interference capabilities requires separate optimization for the control and power circuits. In the control circuit, analog circuits need to add RC low-pass filters at key nodes (such as the operational amplifier input) to eliminate high-frequency noise; digital circuits need to add decoupling capacitors to power pins and I/O interfaces, and use optocouplers or digital isolators for signal isolation. In the power circuit, the length of the drive signal lines needs to be shortened to reduce parasitic inductance; at the same time, dummy loads or absorption capacitors should be placed near power devices (such as IGBTs) to suppress switching overshoot. Furthermore, the PCB layout must strictly divide the analog, digital, and power areas, and avoid ground loop interference through ground plane segmentation and single-point grounding.
Electromagnetic compatibility testing is a crucial step in verifying the effectiveness of the design. Conducted emission testing must be conducted in a shielded room, using a Lithium-Insulated Power Network (LISN) to extract interference signals from the power lines and ensure their amplitude does not exceed standard limits. Radiated emission testing, on the other hand, must be conducted in a semi-anechoic chamber, using an antenna to scan the spatial radiation field strength, locate out-of-standard frequency points, and optimize the shielding design. Immunity testing simulates real-world interference scenarios such as electrostatic discharge, radio frequency radiation, and electrical fast transient/burst effects to verify the equipment's stability under extreme conditions.
Electromagnetic compatibility (EMC) assurance for elevator dedicated power supply (UPS) fan power supplies must be integrated throughout the entire design, manufacturing, and testing process. Through source suppression, path blocking, and terminal reinforcement, combined with rigorous testing and verification, long-term stable operation in the complex electromagnetic environment of elevators can be ensured, providing reliable protection for elevator safety.
