Views: 0 Author: Site Editor Publish Time: 2025-07-11 Origin: Site
— A Must-Read Guide for Vehicle System Design Engineers
In the high-voltage systems of new energy vehicles, high-voltage DC contactors play a critical role in controlling circuit connection and disconnection. However, under complex operating conditions, contactor welding problems frequently occur. Minor issues can cause startup failures, while severe cases may lead to circuit short-circuits, system paralysis, or even safety accidents.
This article provides a practical guide for vehicle system engineers on preventing contactor welding from multiple dimensions, including contact design, arc control, electrical logic, system pre-charge, and product selection.
1. What is Contactor Welding? Why Is It a Major System Risk?
What is Contactor Welding?
Contactor welding refers to the phenomenon where contacts melt and stick together due to arcs or high temperatures during switching, causing failure to open or jamming.
Typical Consequences of Welding:
High-voltage circuits cannot be disconnected, posing significant safety risks.
Contactor failure leads to vehicle inability to start or charge.
Vehicle control system alarms trigger, resulting in high after-sales repair costs.
Issues exposed during system testing or delivery affect project schedules.
2. Root Causes of Welding
Excessive current during break (especially inrush current):
Without a pre-charge circuit, direct closing of the contactor faces large capacitive loads, causing hundreds of amperes of inrush current.
Insufficient arc extinguishing:
Long arc duration concentrates heat on contacts, leading to melting.
Improper contactor selection:
Operating current or voltage exceeds rated values, or contact material is unsuitable for high-voltage platforms.
Excessive switching frequency:
Contacts have insufficient cooling time; continuous closing causes heat accumulation.
Electromagnetic interference causing coil mis-triggering:
Frequent unintended coil activation leads to excessive contact wear.
3. Design Measures Vehicle System Engineers Can Take
✅ 1. Add a Pre-Charge Circuit
Insert a current-limiting resistor between the battery and main circuit. Use a pre-charge relay to gradually charge capacitors and avoid inrush current striking the main contactor.
Pre-charge control sequence:
Close the pre-charge contactor
Delay 500–1500 ms
Close the main contactor
Open the pre-charge contactor
✅ 2. Choose High-Quality Arc Extinguishing Contactors
Prefer products with magnetic blow arc extinguishing plus epoxy resin sealed arc chambers.
Multi-contact structures or arc chute plates effectively disperse heat and prevent arc root erosion.
✅ 3. Select Contact Materials with Strong Anti-Welding Ability
Silver tungsten (AgW) or silver tin oxide (AgSnO₂) contacts have excellent arc erosion resistance.
Thicker contacts and point-to-point contact methods outperform thin sheet contacts.
✅ 4. Use Magnetic Holding or PWM Coil Control
Reduce continuous coil power consumption and avoid heating that affects pull-in/release characteristics.
Prevent mis-triggering and high-frequency repeated closing.
✅ 5. Limit Operating Frequency and Control Cooling Intervals
Recommended contactor switching intervals are at least 1–3 seconds, especially during testing or auto-restart processes.
✅ 6. Incorporate Status Monitoring or Redundant Protection Mechanisms
Monitor contactor status, coil current, and contact temperature.
If mis-triggering or jamming occurs, immediately cut off power via backup circuits.
4. Product Selection Recommendations
Application Scenario Recommended Model Feature Description
EV 400V Platform Estar EVK-150A-750V Silver tungsten contacts, epoxy resin sealed structure, built-in magnetic blow arc path, suitable for medium-high voltage DC circuits
Heavy-duty EV / 800V Platform Estar EVK-300A-1000V High breaking capacity and anti-welding performance, supports high-frequency switching, mechanical life >100,000 cycles, electrical life >10,000 cycles
Energy Storage PCS Side Estar EVK-400A-1500V Designed for high current applications, supports bidirectional breaking and high surge tolerance, suitable for 1500V energy storage systems main circuits
For more models and technical details, please visit our Contactor Product Center.
5. Summary: System-Level Protection > Single-Point Hardware Selection
Preventing contactor welding is never solved by simply choosing a "better contactor." It requires a system-level approach, designing complete electrical logic, protection mechanisms, and control strategies.
Vehicle system engineers, BMS developers, and DC distribution designers should treat "contactor welding" as a key risk item early in the project, controlling it proactively to avoid costly failures later.