Inside a charging pile, the main components include a human-machine interaction panel, fuses, lightning protection devices, contactors, power modules, gun wires, and other modules. Among these, the devices related to electrical protection primarily consist of TVS tubes, fuses, relays, varistors, current sensors, voltage sensors, lightning protection devices, and ground fault relays. These fault protection devices and circuits play an extremely important role, ensuring the charging pile operates reliably under various conditions.

Inside the power module, from the perspective of fault protection design, there are also AC side components like AC fuses, RCD residual current protectors, contactors, ground protection, and surge protection; on the DC side, there are isolation monitoring, relays, fuses, and temperature protection.

Main devices inside the DC charging pile

Main devices inside the DC charging pile

DC charging pile system protection diagram

DC charging pile system protection diagram

e
DC charging pile power module topology

Bidirectional DC topology
Bidirectional DC/DC topology

DC Charging Pile Protection Scheme

  1. As high-power DC charging piles require high voltage and high current AC input, to prevent overload, it’s necessary to use large current fuses with fast blow characteristics. Ensure the current interrupt rating of the fuse is sufficient to exceed the current value on the AC line.
  2. Use surge protectors to absorb voltage transients. Surge protectors can absorb transient currents up to 50 kA. They clamp voltage transients to a safe level, preventing energy from propagating into the circuit and damaging other components. At the same time, add surge protection fuses to safeguard the surge protectors.
  3. For the AC input section, protection should be provided against ground current faults. Use current transformers that detect ground currents less than 30 mA; ground fault protection relays can measure current from the sensor and disconnect the power when a high ground current is detected.
  4. The AC/DC converter circuit requires input fuse protection and transient overload suppression. Use fast blow semiconductor fuses to protect downstream semiconductor components. Consider using Metal Oxide Varistors (MOVs) and gas discharge tubes or a combination of MOVs and thyristors to prevent transients. Low-power charger sub-units only need MOVs or MOSFETs for secondary transient protection.
  5. To protect communication, user interfaces, and access panels and other low-voltage circuits from Electrostatic Discharge (ESD) damage, use Transient Voltage Suppressor (TVS) diode arrays.
  6. Use fast response, high current, high rated voltage fuses to protect the DC output circuits from the impact of load current shorts.
  7. For temperature protection of the charging gun head, use temperature sensors. This requirement is present in the mainstream four charging standards (Chinese, European, American, Japanese).”