Range of transducer’s dedicated to leakage current in PV inverters

6th June 2018
Lanna Deamer


The LDSR model from LEM announced at PCIM 2018, is a low cost and lightweight (25g) component, with a reduced footprint. The LDSR is dedicated to measuring the leakage current of 300mA nominal up to 900mA peak at 2KHz frequency.

Its main application is in transformerless PhotoVoltaic (PV) inverters for the residential market, where it measures AC and DC fault currents and ensures the safety of people around the installation.

The residual or leakage currents that the LDSR model is designed to measure can arise in fault conditions in a number of industrial or power-generation scenarios. Examples include failure modes such as a short circuits or earth faults. The connection of a solar panel to the grid raises safety concerns; if a fault occurs there is a potentially serious safety issue around any human contact with the system.

The sensor is mounted onto a PCB for primary and secondary connections and provides an analogue voltage output.

The LDSR provides a high overload capability up to 3,300A (for a pulse duration of 100ms, and with risetime of 500A/ms), as well as a very high level of insulation between primary and measurement circuits, thanks to long creepage and clearance distances (7.1mm), coupled with a CTI (comparative tracking index) of 600V.

Based on a closed-loop Hall ASIC, the LDSR has been designed with an integrated primary conductor capable of 35A on both the phase and N line. This provides a common mode rejection. The proprietary ASIC ensures high performance accuracy from -40°C to +105°C fulfilling the requirements of the EN 61209 standard.

The LDSR model operates from a +5VDC supply and have a typical current consumption of just 40mA when measuring 300mA as nominal primary residual current; It provides access to its internal reference voltage, and to options such as a test winding and demagnetisation functions.

The product satisfies the needs of PV inverters, offering a competitive price, low dimensions and complying with all regulatory standards. The LDSR is also an alternative to expensive fluxgate solutions due to its small footprint and simple construction.

As well as ensuring safety in solar inverter installations, LEM’s LDSR product is also suitable for a range of applications that includes symmetry fault detection in medium power inverters and failure detection in a range of power sources.

The transducers are CE and UL marked and conform to the industrial standards. LEM offers a five year warranty for each transducer.

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