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5.12 For heating appliances and combined appliances, when it is specified that the
z3 ]* [: t0 }4 v: w. cappliance has to operate at a power input multiplied by a factor, this applies only to heating
! s+ y+ `4 w" |7 s) qelements without appreciable positive temperature coefficient of resistance.1 y$ R- m" {3 z- Q
For heating elements with appreciable positive temperature coefficient of resistance, other than$ k+ E- i% Y; n. |* G/ T
PTC heating elements, the supply voltage is determined by supplying the appliance at rated
* I* O: B5 S# S4 T. }voltage until the heating element reaches its operating temperature. The supply voltage is then8 T4 F0 F3 b& I8 \/ @
Copyright International Electrotechnical Commission+ @4 j3 ?! F7 i5 ^* O% I- U
rapidly increased to the value necessary to give the power input required for the relevant test,- k7 ~% z2 @# y9 o# H2 h* ?
this value of the supply voltage being maintained throughout the test.
7 A& I, A; c d0 vNOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input E9 N5 M( v# v9 D+ J
of the appliance in cold condition differs by more than 25 % from the power input at operating temperature.
{: J2 N* R2 h+ C+ m, p5.13 The tests for appliances with PTC heating elements and for heating appliances and
. S. b- Z; A3 icombined appliances where the heating elements are supplied via a switch mode power7 r, Y, n3 I4 l6 b
supply are carried out at a voltage corresponding to the specified power input.
' {' N8 m4 v+ M9 QWhen a power input greater than the rated power input is specified, the factor for multiplying
8 V- g% ]2 L$ I+ K! athe 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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