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5.12 For heating appliances and combined appliances, when it is specified that the5 {% m5 R7 W0 T* F2 _9 v/ E( ?2 g
appliance has to operate at a power input multiplied by a factor, this applies only to heating) h! e- e6 O! D' Q# h$ \" e
elements without appreciable positive temperature coefficient of resistance.: v. K4 ^ r1 Z+ v( `
For heating elements with appreciable positive temperature coefficient of resistance, other than D: M) {2 A9 I, D' ~
PTC heating elements, the supply voltage is determined by supplying the appliance at rated
. C+ T% b. _. Uvoltage until the heating element reaches its operating temperature. The supply voltage is then: y, A) b$ |' \0 _: D9 N' f; S) }
Copyright International Electrotechnical Commission+ I7 ?8 y) n; J
rapidly increased to the value necessary to give the power input required for the relevant test,
5 L; ~8 {9 ^2 q( V9 o" x, ~this value of the supply voltage being maintained throughout the test.& ~) [1 n9 A6 Z/ h
NOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input
: `9 u6 r, f: f- B+ }9 hof the appliance in cold condition differs by more than 25 % from the power input at operating temperature.
* T" f' C1 U q0 S3 v/ d6 u$ c5.13 The tests for appliances with PTC heating elements and for heating appliances and4 O3 A) A+ p3 O' H6 D4 n6 ~$ O
combined appliances where the heating elements are supplied via a switch mode power
/ m% c; i: m4 g: w5 v9 ?supply are carried out at a voltage corresponding to the specified power input.
* T( |+ T' Q R5 Z: d/ yWhen a power input greater than the rated power input is specified, the factor for multiplying
( n) f2 D/ L% r4 W/ e* Cthe 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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