IEC 62044-3:2000 pdf download

IEC 62044-3:2000 pdf download.Cores made of soft magnetic materials – Measuring methods – Part 3:Magnetic properties at high excitation level.
4.2.2 The use of a single winding both for excitation and voltage sensing is recommended if
— the coupling between the exciting winding and the voltage sensing winding is so reduced that it results in a non-negligible error in the determination of the measuring induction A in the core;
— the inter-winding capacitance is too high:
— there is no measuring circuitry contra.indication against the direct connection of the exciting winding to input(s) of measuring Instruments.
NOTE When single winding is used, ills recommended that its resistance be made as low as possible to make the winding ohmic power toss negligible compared to the Dower loss in the core,
The use of separate exciting and voltage sensing windings (double winding) is recommended if. for whatever reason, the exciting winding should be galvanically separated from the voltage and the current measuring instruments, for example, to avoid a floating or d.c. connection to their Inputs.
NOTE I When it’. ezc’t’ng and voltage s.nsing windings ar, used, its crilical to make their magnetic coupling coetlicieni as close to 100% as possible.
NOTE 2 When the voltage needed for calculation of the •nduction in the oore is measured across the voltage sensing winding th,n only the power loss in the core is determined with the •xcius.on of th. ohmic power loss in the Currentcarrying (exciting) winding
NOTE 3 Thi us. of two windinOs is recomm•nd.d at more than 200 kHz.
4.3 Mounting of cores consIsting of more than one part
The core, which consists of more than one part and which is to be assembled around the measuring coil, shall be held together with glue, tape or a clamping device throughout the measurement.
Whichever method is used to join the core parts together, it shall have the following characteristics:
— distribution of the joining force uniformly over the mating surfaces, without the introduction of bending stresses in the core;
— holding of all the core parts rigidly and without changing the position to each other;
— when a specified clamping method is used, an initial over-force of about IC $ shall be applied when the core is closed, in order to break down fine irregularities between the cleaned mating surfaces. Next, the specified clamping force ±5 % shall be applied:
— keeping the joining force constant within ±1 % during all measuring operations within all measuring conditions, including the full specified temperature range.
The mounting of such cores shall be carried out in accordance with the following instructions,
The mating surface shall be inspected for damage and cleanness. Damaged cores shall not be used. The mating surface shall be cleaned by non-abrasive means, for example, by rubbing gently on a dry washing-leather. Next, the mating surfaces shall be degreased if they have to be glued. Dust particles shall be blown off with clean dry compressed air. The mating surfaces shall never be touched with bare fingers. The core parts shall then be assembled around the measuring coil, the latter being locked in position with respect to the core by suitable means, for example, a foam-washer. The core paris are centered and glued or placed in clamping device, The glue, if used, shall be spread evenly on the mating surface to form a film as thin as possible and then properly hardened.
In the case where the clamping device is used, the clamping force specified in the relevant specification shall be applied. The glued. taped or clamped cores shall relax under the specified conditions (see clause 3 of IEC 60367.1) for a time sufficient to allow any variation of stress effects, due to clamping, gluing or taping, to become negligible.
4.4 Measuring equipment
Any suitable measuring equipment may be used. Examples of appropriate Circuits are given in annexes A to E.
In addition to any requirement specified for the particular method and/or measuring Circuit used, the following general requirements shall be met.
4.4.1 To ensure the induction (field strength) mode of excitation, the output impedance of the exciting source shall be low (high) compared with the series impedance of the exciting winding of the measuring coil assembled with the core under test and the current sensing resistor.
4.4.2 When the sinusoidal waveform of excitation is specified, the total harmonic content of the excitation source shall be less than 1 %. When square pulses are specified, the relevant requirements of clause 1601 IEC 60367-1 shall be met.
4.4.3 During the period of measurement, the excitation amplitude variations shall not exceed
±0.05 % and the frequency stability shall be adequate for the measuring method and the equipment used.
4.4.4 The frequency range of voltmeters and other voltage sensing instruments shall include all harmonics of the measured voltage having amplitudes of 1 % or more of their fundamentals. This frequency range shall be specified in the relevant instrument specification.
4.4.5 The voltmeters and other voltage sensing instruments used shall be high-impedance instruments, the connection of which will have Only a negligible effect on the measuring circuit, especially at high frequencies. The probes f a high-input resistance and a low-input capacitance can reduce the load effects.