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5.12 For heating appliances and combined appliances, when it is specified that the
0 p* ]- N8 k3 |! @; qappliance has to operate at a power input multiplied by a factor, this applies only to heating" U" w3 \3 P3 v* v) p- a' w
elements without appreciable positive temperature coefficient of resistance.
( W5 B* p' E$ m1 L6 X; l( C. |For heating elements with appreciable positive temperature coefficient of resistance, other than
8 E U2 m- k$ }- r3 C5 e# zPTC heating elements, the supply voltage is determined by supplying the appliance at rated
3 I% ^% }" \- m; Mvoltage until the heating element reaches its operating temperature. The supply voltage is then; z# e' e6 |& Q" r; e
Copyright International Electrotechnical Commission- B9 o1 x% V) x; ^3 h
rapidly increased to the value necessary to give the power input required for the relevant test,5 z: J) k6 [+ R4 h4 M8 V
this value of the supply voltage being maintained throughout the test.
1 q; @: O t1 U( S; M. ]NOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input
! k. r4 }9 H9 v5 u: N$ xof the appliance in cold condition differs by more than 25 % from the power input at operating temperature.; i% k2 q' X* Y
5.13 The tests for appliances with PTC heating elements and for heating appliances and4 {' A3 e+ [* Z3 ?
combined appliances where the heating elements are supplied via a switch mode power4 u+ u Z2 E6 _4 _" s- K2 A
supply are carried out at a voltage corresponding to the specified power input.
% K, }; Q1 S0 H3 `" z: yWhen a power input greater than the rated power input is specified, the factor for multiplying! o7 c" Z8 f9 \* D4 g& W6 e8 J5 ?
the 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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