Open-loop current sensors measure AC and DC currents and provide electrical isolation between the  circuit being measured and the output of the sensor (the primary current is measured without electrical contact with the primary circuit, providing galvanic isolation). Less expensive than their closed-loop cousins, open-loop current sensors are generally preferred in battery-powered circuits given their low-operating power requirements and small footprint features.Closed-loop sensors measure AC and DC currents and provide electrical isolation.
They offer fast response, high linearity, and low temperature drift. The current output of the closed-loop sensor is relatively immune to electrical noise. The Closed-loop sensor is sometimes called a ‘Zero-Flux’ sensor because its sensorelement feeds back an opposing current into a secondary coil, wound on the magnetic core to zero the flux produced in the magnetic core by the primary current. Closed-loop sensors are often the sensor of choice when high accuracy is essential.

Leakage current of the photovoltaic system, which is also known as the square matrix residual current, is essentially a kind of common mode current. The cause is that there is parasitic capacitance between the photovoltaic system and the earth. When the parasitic capacitance-photovoltaic systemgrid forms a loop, the common mode equipped with a industrial frequency transformer, because of the relatively high parasitic capacitance between the transformer windings in the loop, the common mode current generated by the common mode voltage in the loop can be suppressed to a certain extent. However, in a photovoltaic system with no transformer, the loop impedance is relatively low, and the common mode voltage will form a large common mode current, ie, leakage current, on the parasitic capacitance between the photovoltaic system and the earth.

Hazard of leakage current
If the leakage current in the photovoltaic system, including the DC part and the AC part, is connected to the grid, it can cause problems such as grid-connected current distortion and electromagnetic  interference, so as to affect the operation of the equipment in the grid. In addition, leak current can also electrify the solar inverter casing, thus threatening physical safety.

Standard and detection of leakage current
According to the 7.10.2 regulation of NB32004-2013 / IEC 62109-1:2010 standard, in any case where the solar inverter is connected to the AC grid and the AC breaker is turned off, the inverter should provide leak current detection. Leak current detection should be able to detect the total (including the DC and AC parts) effective value current, continuous residual current.

Sinomag's residual current detection sensors not only meet the requirements of the solar industry, but wherever a leakage current has to be detected in order to avoid damage to a system or even danger to people, these products are a precise and cost-effective solution.

Chip Level Current Sensor especially designed for automotive application. The compact SMD package without primary current bus bar can be integrated into power electronics.

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