Equivalence of Measurements on Soft Magnetic Materials in the U.K. and Measurements for Operational Conditions
Measurements on soft magnetic materials were made to determine the measurement capabilities available to the partners of a government-funded collaborative research project, with 16 partners from industry and academia. One of the objectives of this project was the development of advanced magnetic materials for novel electrical machines for use in harsh environments such as gas turbines. To establish the measurement confidence necessary to deliver this project objective, an equivalence study was undertaken. A reference core of soft magnetic material that has been measured over a period of many years at the National Physical Laboratory (NPL) was distributed and the dc and ac properties were measured. The measurement systems of the three laboratories are independent and this ensured that no correlations that could skew the results existed. In the analyses, the measurements at NPL were used as the baseline. With the core capabilities established, it was possible to develop the new measurements required to deliver the overall project objectives. At NPL, a standard permeameter method was modified for the measurement of strips. This was incorporated into a stress machine to measure the dc properties of the soft magnetic materials used by the partners, at stress levels of up to 700 MPa. The results for seven materials are presented and the changes in the properties with applied stress compared to establish which materials exhibit favorable properties.
Dynamic Error Correction for Magnetic Property Measurement
In this paper, we present an efficient technique to compensate the dynamic offset error in the voltamperometric method, for the subhertz characterization of hysteretic magnetic materials. The integration of the output voltage at the secondary winding inherently tends to cumulate the residual offset voltage that is not constant over long experiments as often supposed. Slight variations of the residual offset voltage due to multiple effects make simple linear detrend techniques ineffective and limit the achievable accuracy up to make useless the obtained data. We first use custom signals to identify the thermal and electrical dynamic models of the measurement setup, and further we remove the model-based expected trends. The results confirm the effectiveness of the proposed method for error compensation, with accuracy improvements up to 40 dB.
Effect of various kinematic parameters of mine hoist on fretting parameters of hoisting rope and a new fretting fatigue test apparatus of steel wires
The effect of various kinematic parameters of mine hoist on fretting parameters of the hoisting rope was investigated and a new fretting fatigue test apparatus was designed. A simulation model of the rope tension was presented to examine the role of various kinematic parameters on the rope tension and tension amplitude during lifting. Ranges of fretting parameters of the rope during lifting with different kinematic parameters were determined. The results show that different kinematic parameters induce different modal shapes of the vibrating systems during lifting, which results in distinct ranges of fretting parameters of the rope.