The challenges for E-Mobility charging applications

21st November 2016
Enaie Azambuja

Once regarded as a temporary hype, the e-mobility sector is growing fast and strong with some predicting it could take a 35% share of car sales by 2035. According to analysts at EV Volumes plug-in EV are charging forward worldwide, with more than 2 million vehicles expected to be on the roads by the end of 2016. In the first half of 2016 around 312,000 plug-in electric cars were sold — a nearly 50% increase over the first half of 2015.

Main driver of the increased sales is China, which has become “the” market and manufacturing base for electrically chargeable vehicles. The growing market poses new challenges for electromechanical components to meet ever growing demands for secure operation, miniaturisation and cost-efficiency.

Power relays are designed for use in electric vehicle charging devices, electric drive trains or any applications requiring high loads to be switched and carried. Because of high voltages that can occur on both side of the EV charging cable, fulfilling safety and supervisory demands is essential.

The charging of electro vehicles may take place in different manners, either with 1 or 3 phase household level AC voltages and respective currents, or by use of DC quick charging at voltages of 200 to 600V at currents up to 400A.

In the U.S. there is the SAE J1772 standard, while in Europe and China the IEC61851 standard specifies four modes of EV charging. Charging via IEC mode 2 is a particular challenge for switching relays.

There are higher currents and a control and protection equipment is required to be integrated into the charger cable (In-Cable Control and Protection Device – IC-CPD). This IC-CPD protects from electrical hazards in case of isolation failures and is defined in IEC62752. In its newest edition the IEC62752:2016 requires a peak current Ip of up to 1.5kA in case of short circuits.

“At this high current load, electrodynamic forces (Lorentz Force) occur which counteract the contact force of the relay”, explains Alexander Stöckel, Product management - Electromechanical Components at ZETTLER electronics.

“In an extreme case, the temperature increases so much that the contacts weld. That’s why we have developed special contact arrangements, that withstand highest momentary currents and even increase the contact performance due to magnetic force.”

The new AZSR116/132/140 relay series by ZETTLER also feature a potential free N.C. (1 Form B) monitoring supervisory contact as required by IEC62752:2016, making them ideal for applications with high security and safety demands in the EV market.

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