Basic Properties of High Voltage DC relay

The working platform voltage of new energy electric vehicles is generally high. The working voltage of passenger cars is usually above 370V, and that of buses will reach above 576V, much higher than the 12V/24V of traditional vehicles. Therefore, the high-voltage Dc Relay used in conjunction with them must be able to withstand the high working voltage and reliable closure and opening under high-voltage load conditions.

The rated power of the electric motors in new energy passenger cars and buses is generally above 30KW and 80KW respectively, with peak values reaching 60KW and 160KW respectively. According to the voltage platforms mentioned above, the current will reach approximately 200A and 300A respectively. Under the dual pressure of product performance and cost, it is required that with the same volume, the product has strong load resistance and at the same time, it should have an instantaneous overload capacity several times the rated load current; or under the same load resistance capacity, the product should have a smaller volume.

The high-voltage DC relays used in new energy vehicles not only need to have the basic functions of withstanding high voltage and carrying sufficient current, but also need to resist the impact of the huge current of the capacitive load at the moment of closure. This current is usually several to several tens times the rated current of the load. Conventional relays cannot withstand this instantaneous current impact. This impact current's hazard is that it is very likely to cause the contact points to stick, the contact points to fail to separate, the power supply to be cut off out of control, and in severe cases, it can cause accidents such as vehicle destruction and casualties, which is extremely harmful. Therefore, the DC relay products for new energy vehicles should have good shock resistance performance.

Arc is an inevitable problem during the closure and opening of relay contact points. It greatly reduces the service life of the relay contact points. Some special rapid arc extinguishing means are adopted to reduce the arc energy and reduce the damage to the relay contact points, thereby extending the product's service life. Therefore, strong arc extinguishing ability is also a basic characteristic that relays need to have.

The operating conditions of vehicles during operation are complex. In emergency situations, such as when the electrical system shorts, the instantaneous current in the circuit surges. At this time, it is required that the relay can smoothly cut off the circuit under the extreme large current without causing abnormal conditions such as contact point sticking or relay explosion, to prevent safety hazards such as battery over-discharge, short circuit, and explosion. This requires the contact points of the relay to have good resistance to shock and anti-sticking ability.