Making an RCD for an EV wall box

[Flyback]

Hi,
We wish to make a RCD for an EVSE single phase “wall box”. We will use a simple CT for the 30mA imbalance detection. This may get “blinded” by any DC leaking in either line or neutral.

Therefore, we will also have a second CT the same as the first one, but will constantly also inject 30mA AC 50Hz through its aperture with a wire loop. As soon as this second CT does not detect the 30mA , then that means it has been “blinded” by a DC current flow in either line or neutral, so therefore we turn off the relay.

(We will inject the 30mA with constantly alternating polarity.)

Would this pass regulations? Why not? It surely guarantees safety, and is far cheaper than offtheshelf RCDs for 30mA/6mA which are £30 upwards.

 

[rjenkinsgb]

You are dreaming. You cannot make and sell a commercial design for £30, unless you have near unlimited backing and they will sell in thousands to cover costs.

It needs testing and certification / CE approval / EMC tests etc. to be fit for use in a safety-related and non low voltage application and you would be liable for any damage or injury if it were not certified and you did not have docuemtary proof and independent evidence that it would work as required under all possible fault conditions.

The testing and approval for such things costs thousands.

(And the simple way of avoiding problems with a wound CT is to use a hall type current sensor, an "electronic current transformer", that can respond to both AC and DC. That's quite probably what the commercial units use).