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High Voltage DC Contactors are used in DC Fast charging Stations
5 Posts

What kind of Contactors are used in DC Fast charging Stations?

Please correct me if I am wrong, I believe we need the utilization category of DC-13 for DC Fast charging.
Rated current -125A, Rated Voltage -120Vdc

I have seen companies using DC-1 utilization for the same like Dongya, TE, Little Fuse.

Are these okay for DC switching?

Assuming 16 closing and opening Contactor operation in a day with current as much as 125A, 120VDC

Should we look for contactors of  DC-1 utilization instead of DC-13.

Any opinions on this one? Kindly share with some technical details.

Also generally what should be the ideal Making and Breaking capacity for Contactors for EV Charging.
As per IEC -60947-5 it should be same as Rated current for DC-13 Catagory.
Appreciate the advice.

5 Replies
3509 Posts
A contactor in such service would not normally be expected to break under full load, i.e in mid charge - that way the contacts have a short and brutal life, as I think you observe. Rather better is when the charger electronics is used to ramp the current up after contact, and down to a low value before disconnection, unless there is a malfunction requiring an emergency stop.
Recalling that DC1 is for resistive loads, and DC13 is really for things with undamped stored magnetic energy like solenoids in scrap yards, where there may be a big back EMF on disconnection. There are inductors in a car charger, but they are not the main energy storage component. To make a charger appear as a DC1 class load or better should be possible, especially with carefully chosen subbing circuits to absorb transients.
However, it may have to survive a few of the malfunction events in its lifetime, so to have a bit in hand is always good practice.

Rob Eagle
152 Posts
When interrupting DC you need to get as much air between the contacts as quickly as possible to break the arc, a good way of doing this is to have switching contacts in series.
1 Posts
Fast charging aims to recharge EV batteries within a short period similar to that for gasoline refuelling of conventional vehicles. The time necessary for fast charging is about 20 minutes for charging up 80% capacity. Thus, the total travelling distance of EVs can be greatly extended, provided that there are sufficient fast charging stations on the way. The key to fast charging stations is the off-board fast charging module, which can output 35 kW or even higher. The corresponding voltage and current ratings are 45–450 V and 20–200 A, respectively. As both power and current ratings are so high, such recharging facilities have to be installed in supervised stations or service centres.
3509 Posts
If designing systems from scratch, even 450V seems quite  low for the traction voltage, certainly a low voltage by the standards of BS7671, and 200A makes for a rather unwieldy cable unless it is liquid cooled - it may be better to move to higher voltages and a lower current - even 100A at 900V would be better, though  25mm2  of copper per core or more would still be needed, and that would  stay comfortably below the threshold for being considered a high voltage in the UK and Europe (1000V rms AC and 1500V DC is the magic boundary, but really a totally arbitrary number that could be exceeded with impunity - mining operations frequently trail what are in effect very heavy extension leads up to the1k3 and  3k3 mark in very hostile places and robust connectors exist for that.   examples ).
It may not be so relevant but there is also  a very large background of experience for train traction systems at levels in the 750-900V range, and designs of components such as switches, interlocked connectors and contactors that suit this  are available and understood.


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