VAC's New Cores and Inductive Components


electronica 2010 Hall B5, Stand 119

VACUUMSCHMELZE GmbH & Co. KG (Hanau) will again attend electronica from 09 to 12 November 2010. At the VAC stand in Hall B5, Stand 119, the Cores and Inductive Components division will demonstrate the materials expertise of the Hanau-based company, presenting new and established products from the power electronics sector. In addition to the new range of UL1446-compliant common mode chokes and AC/DC sensitive differential current sensors, VAC will present its new customized CMC Sample Kit at the Munich trade show. The stand will also show high-voltage insulation drive transformers for modern power semiconductors and cut cores in nanocrystalline VITROPERM®. The Sample Kit 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 48 A and operating voltage up to 1000 V. Common mode chokes from VAC use toroidal tape-wound cores of VITROPERM®, a nanocrystalline magnetic alloy which can be tailored to provide a wide range of permeability levels between 5,000 to over 150,000. With a high saturation flux density of 1.2 T, VITROPERM® cores allow the dimensions of chokes to be reduced by a factor of three in comparison to conventional ferrite chokes. Despite their high inductance, VAC 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 extremely 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. A focus at the stand this year will be VAC's family of AC-DC-sensitive differential current sensors. These DI sensors form the core of residual current monitoring units (RCMUs) compliant with the VDE 0126 standard for transformerless solar inverters. The DI sensors render the installation of expensive 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. VAC DI sensors offer a range of additional functions, including sensor core demagnetization, which can be triggered by the supply voltage or as required. VAC's new range of current sensors for PCB assembly with integrated electronics has achieved outstanding market success in recent years. VAC has patented the principle of the closed-loop sensor with magnetic probe as the zero field detector, which is characterised by extremely high-precision current detection. The new VAC current sensors concentrate practically all their electronics in a custom-designed signal-conditioning IC produced in partnership with a leading semiconductor manufacturer. The sensors offer outstandingly 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 superior properties and cost-effective design of VAC current sensors have ensured them a central role in the forefront of photovoltaic and industrial inverter applications. VAC's new drive transformers for IGBT control (600 V link voltage) feature:

  • low sensitivity over a broad operational temperature range from
  • - 40+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
  • 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. VAC's 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 extremely 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 synchronized large-scale inverters.