Customised CMC sample kit from VAC contains 24 selected common mode chokes from the new UL1446 type series, comprising dual winding chokes for single-phase applications and three and four winding chokes for three-phase applications. The chokes are designed for operating currents ranging from 4 to 48A and operating voltage up to 1000V. Common mode chokes from the company use toroidal tape-wound cores of Vitroperm, a nanocrystalline magnetic alloy, which can be tailored to provide a range of permeability levels between 5000 to over 150,000. With a high saturation flux density of 1.2T, Vitroperm cores allow the dimensions of chokes to be reduced by a factor of three in comparison to ferrite chokes, claims the company. Despite their high inductance, the chokes typically have a low number of turns and large copper cross-section, thereby reducing copper losses and improving system efficiency. Nanocrystalline common mode chokes deliver broadband attenuation, determined in the low-frequency range by the high level of material permeability and at higher frequencies by the low winding capacity. In many cases, this broadband attenuation enables EMI filtering to be simplified and even permits the number of passive components to be reduced by reducing the number of filter stages. The family of AC/DC-sensitive DI (differential current) sensors form the core of RCMUs (residual current monitoring units) compliant with the VDE 0126 standard for transformerless solar inverters. The DI sensors render the installation of DC-sensitive residual current devices. The operating current, supply return current conductor and where necessary external test current are routed through the sensor, which measures only the current difference, i.e. the residual current to an accuracy of 1.5% of the allowable residual current of 300mA. Output is a voltage proportional to the differential current. The sensors offer a range of additional functions, including sensor core demagnetisation, which can be triggered by the supply voltage or as required. The company has patented the principle of the closed-loop sensor with magnetic probe as the zero field detector, which is characterised by high-precision current detection. The new current sensors concentrate practically all their electronics in a custom-designed signal-conditioning IC produced in partnership with a semiconductor manufacturer. The sensors offer accurate measurements together with low temperature dependence and low long-term drift. The sensors are compact with high maximum and continuous current capability. The range includes sensors with unipolar or bipolar power supply and with selectable output voltage or output current. The properties and cost-effective design of the sensors have ensured them a central role in the forefront of photovoltaic and industrial inverter applications,claims the company. New drive transformers for IGBT control (600V link voltage) feature low sensitivity over an operational temperature range from -40 to +100°C; low leakage inductance for high-precision pulse transmission; compact size due to use of cores with approximately three times the flux density of ferrite; 100% high-voltage tested; and partial discharge tested and compliant to international standards such as EN 50178 or IEC61800-5-1. The new transformers will initially be available as pin connected (PTH) transformers, with models for surface mounting (SMD) custom-produced on request. The cut cores, produced from nanocrystalline Vitroperm, are used for transformers in applications where low loss and/or low noise are critical. Compared to conventional core materials such as amorphous iron or silicon (6.5%)-iron alloys, losses of Vitroperm cores are two to four times lower at frequencies above one kilohertz. Cut cores with multiple airgaps allow the reduction of stray field losses in the air gaps and thus the overall losses in a transformer. In addition to core geometry and air gap dimensions, a further factor impacting on noise is the inherent magnetostriction of the core material. At a factor of 10 to 100 lower than that of amorphous iron or silicon-iron alloys, Vitroperm has low magnetostriction. Vitroperm also achieves a saturation induction of 1.2 Tesla and a curie temperature of over 580°C. Cut cores are impregnated with resins which are suitable for temperatures up to 150°C. Further areas of application for Vitroperm cut cores include single or multi-phase power or output chokes for high current ripple and interphase transformers for parallel operation of synchronised large-scale inverters.
