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5.12 For heating appliances and combined appliances, when it is specified that the
1 h, S! Y, _5 h% M/ M( sappliance has to operate at a power input multiplied by a factor, this applies only to heating2 K7 U+ N; H# I' n; ]
elements without appreciable positive temperature coefficient of resistance.9 a' D: j8 S$ B1 Q- d
For heating elements with appreciable positive temperature coefficient of resistance, other than; Y5 I+ | ?( _" w9 ` X1 C
PTC heating elements, the supply voltage is determined by supplying the appliance at rated* }4 `$ _ X5 o# {, i f( ^
voltage until the heating element reaches its operating temperature. The supply voltage is then
9 s0 p K1 Q5 H( D; SCopyright International Electrotechnical Commission) B% y( l( K4 @8 Y" \
rapidly increased to the value necessary to give the power input required for the relevant test,
7 m9 w. [: N. H }% _! I$ Ithis value of the supply voltage being maintained throughout the test.
- D v" v, ]3 nNOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input b: ~2 ]% A* P4 X- R2 r
of the appliance in cold condition differs by more than 25 % from the power input at operating temperature.
" B' |5 N" `0 D/ v" ~) U5.13 The tests for appliances with PTC heating elements and for heating appliances and
7 |0 }4 @+ e9 ^, E7 R8 g" Qcombined appliances where the heating elements are supplied via a switch mode power
/ Q6 Q* E( Y6 E% b0 b' i% Csupply are carried out at a voltage corresponding to the specified power input.
9 f% B+ i' K" B u) i8 VWhen a power input greater than the rated power input is specified, the factor for multiplying
- _0 y6 z$ W \! N& rthe voltage is equal to the square root of the factor for multiplying the power input. |
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发表于 2012-10-14 22:14
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