IEC 60076-10:2001 pdf download

IEC 60076-10:2001 pdf download.Power transformers -Part-10: Determination of sound levels.
3.9
prescribed contour
horizontal Irne on which the measuring po5itions are located. spaced at a definite horizontal distance (the measuremen: dstaice) from the principal iadiatng surface
3.10
measuremint distance. .i
horizontal distance between the principal radiating surface and the ‘measurer-erit surface”
3.11
measurement surface
hypothetical surface enveloping the source and on which the r,easuremant points are located
3.12
background noise
A-weighted sound pressure evet with the test object inoperative
4 Instrumentation and calibration
Sound p’essure measurements shall be made using a type 1 sound level meter complying with IEC 60651 and calibrated in acco’dance with 5.2 of ISO 3746.
Sound intensity measurernen’s shall be made using a class I sounc intensity insturnent complying with IEC 61043 and calibrated in accordance with 6,2 1 ISO 9614-1 The frequency range of the measuring equipment Shall be ecapteci to the frequency spectrum of the test Object, that is. an appropria”e microphone spacer sys:em shall a chosen in crder to mlriimi7e systematic erors
The measuring equipment shall os calibrated immediately before anti after the measurement sequence If the calibration changes by more than 0,3 aS, the measurements shall be declared invalid aid the test repeated.
5 Choice of test method
Either Sound pressure or sound intensity measjren,ents may be used b determine the value of the sound power level Both methods are valid and either can be used, as agreed between manufa:Iure’ and purchaser at the lime of pfacing the order
The Sound pressure method of r,easuren,enl described ii this standard is in accordarce with iSO 3746 Measurements made in conlormity with this standard tend to result in standard deviations o’ reproducibility between determinations made in different aboratories which are less than or equal to 3dB
The sound intensity method of nieesuremer,t described in this standard is in accordance with ISO 9614-1 Measurements made in confrmity with this standarc tend to result in standard deviations of reproducibility be’eeen determinations made in different Iabora1ores which are less than or equal to 3 dB
6 Load conditions
6.1 General
Load condition(s) shall be agreed between the manufacturer and purchaser at the time of placing the order, If a transformer has a very low no-load sound level, the sound due to toad current can influence the total Sound leve in service The method to be used for summmnq the no-load and load current sound levels iS given in clause 14
Curreit taken by a reactor is dependent on the voltage applied and consequently, a reactor cannot be tested at no-load, Where sufficient power is available in the factory to permit full energization of reactors, the rethods to be followed are the same as those for transformers. Alternatively. rneasurement5 may be mace on-site if conditions are suitable.
Unless otherwise specifei. the tests shall be carried out with the tap-changer (if any) on the principal tapping However. Pus tap position may not give the maximum sound level in service In addi:.on, when the transtormer is fl service, a superposition of the flux at no.load conditions and the stray flux occurs which causes a change in the flux density in certain parts of the core Therefore, under special cond tons of intended application of a transformer (particularly variable flux voltage variation), it may be agreed to measure the sound levels on a tapping other than the principal tapping, or with a voltage other thanihe rated vollage on an untapped winding This shall be clearly indicated in the test report
6.2 No.load current and rated voltage
For measurements made on the test object with or without its auxiliary cooling plant, the test object shall be on no-Icad and excited at the rated voltage of sinusoidal or practically sinusoidal waveform and rated frequency. The voltage shall be in accordance with 10,5 of IEC 60076-1 If a transformer s fitted with reactor-type on-load tap-changer equipment where the reactor may On certain tap-change positions be permanently energzed. the measurements shall be made with the transformer on a tapping which involves this condition and which is as near to the principal tapping as possible The excitation voltage shall be appropriate to te tazping in use This shalt be clearly indicated in the test report or North American appltcatons. the sound level tests shall be made at no-load in accoidance win national requirements
6.3 Rated current and short-circuit voltage
In order to decide whether it is significant to per1nm oad current Sound measurements, the
-nagritude of the load current sound power level can be roughly estimated by equation 4.
IN is tound to be 8 dB or more below the guaranteed sond power level, load curren’ Sound measurements are nor appropriate
When these measurements are recuired, one winding shall be short-circuited and a sinusoidal voltage as defined ii 10 5 of IEC 60076-1 applied to the other winding at the rated frequenCy. The voltage shall be gradually increased until rated current flows in the short-circuited winding.