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5.12 For heating appliances and combined appliances, when it is specified that the
8 S9 m) B! h+ S9 R, C1 happliance has to operate at a power input multiplied by a factor, this applies only to heating1 L8 t; {+ b5 a$ m: f- a0 T9 X
elements without appreciable positive temperature coefficient of resistance.9 l! h/ S4 k5 h. @' i
For heating elements with appreciable positive temperature coefficient of resistance, other than/ V% G d. ?% ~" v8 E1 d
PTC heating elements, the supply voltage is determined by supplying the appliance at rated
6 \! i5 i# O4 Y* ^. n: ^ mvoltage until the heating element reaches its operating temperature. The supply voltage is then, ]. |; q9 a/ d' b/ p6 O2 h8 y7 ?
Copyright International Electrotechnical Commission
0 `: h4 X8 C- o( Vrapidly increased to the value necessary to give the power input required for the relevant test,
$ `- U) b6 V6 Z; h+ e! m# mthis value of the supply voltage being maintained throughout the test.' d: g" \0 @' G
NOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input2 E) _2 ^ S4 V" M8 X" A# [
of the appliance in cold condition differs by more than 25 % from the power input at operating temperature.
$ f0 P& @1 `. |1 q2 J$ M5 {5.13 The tests for appliances with PTC heating elements and for heating appliances and; X& {, p% R3 y
combined appliances where the heating elements are supplied via a switch mode power
$ @" g7 o- d1 Z) P9 _5 [/ W5 p2 csupply are carried out at a voltage corresponding to the specified power input.
0 t* J! }% H1 M: C) J9 n0 i2 tWhen a power input greater than the rated power input is specified, the factor for multiplying
* h4 J& ^% a; X! e' E; `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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