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5.12 For heating appliances and combined appliances, when it is specified that the2 K# |5 K9 A2 X/ A
appliance has to operate at a power input multiplied by a factor, this applies only to heating- }7 T Q/ A4 Z# ~% U
elements without appreciable positive temperature coefficient of resistance.
. m! j2 U. e b I( V6 l- L; fFor heating elements with appreciable positive temperature coefficient of resistance, other than9 q8 H ~" J+ S( H5 c0 r( T- E' m
PTC heating elements, the supply voltage is determined by supplying the appliance at rated
1 @# `) n7 j3 P" j9 Wvoltage until the heating element reaches its operating temperature. The supply voltage is then
) U5 @! X+ O W' N5 `3 ^. VCopyright International Electrotechnical Commission0 [. i5 g/ N- p/ K
rapidly increased to the value necessary to give the power input required for the relevant test,
- [7 P. j+ F v# b" ^7 qthis value of the supply voltage being maintained throughout the test.% h, T3 g1 i/ d( o: r
NOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input
& N! C( P! a3 R# w0 h; r# C5 Iof the appliance in cold condition differs by more than 25 % from the power input at operating temperature.
3 D/ q4 O" I: I) H. Q" z. z! p5.13 The tests for appliances with PTC heating elements and for heating appliances and; I0 q. z2 u5 W) b8 B J4 B3 t
combined appliances where the heating elements are supplied via a switch mode power
$ k3 p9 I* a0 ]3 j2 ysupply are carried out at a voltage corresponding to the specified power input., s" S( F5 y, s; c) d$ x3 F, U7 c
When a power input greater than the rated power input is specified, the factor for multiplying
% o- l( ]# \: L2 Z7 K# Vthe 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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