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5.12 For heating appliances and combined appliances, when it is specified that the
* ]. R& @+ V4 Y( _appliance has to operate at a power input multiplied by a factor, this applies only to heating8 c, X; d N6 k/ U( Z1 ^5 |8 g# n
elements without appreciable positive temperature coefficient of resistance.
4 y- k t$ w3 Q! c! | hFor heating elements with appreciable positive temperature coefficient of resistance, other than0 u% W/ f9 p' {$ p# ?0 ] m0 y
PTC heating elements, the supply voltage is determined by supplying the appliance at rated
" L$ l- \5 P: r7 u& z& xvoltage until the heating element reaches its operating temperature. The supply voltage is then e2 H* g( R; R9 Y& P" v( _
Copyright International Electrotechnical Commission
# |5 B4 w8 y6 z' M6 }$ H* Brapidly increased to the value necessary to give the power input required for the relevant test,
. _$ z0 k5 v" d: K/ u- S$ Wthis value of the supply voltage being maintained throughout the test.
5 B1 D. S# E- h- W8 ONOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input
. h2 b9 U7 N: V# R( j- j' j aof the appliance in cold condition differs by more than 25 % from the power input at operating temperature.$ \7 N ]4 v. q8 p8 t
5.13 The tests for appliances with PTC heating elements and for heating appliances and6 h# D) P+ f# Y' _5 L8 g
combined appliances where the heating elements are supplied via a switch mode power2 K& q, y. W2 F% \. @+ Q
supply are carried out at a voltage corresponding to the specified power input.
' C0 L! F0 H5 d0 Y* N) @" G3 MWhen a power input greater than the rated power input is specified, the factor for multiplying
5 @# v5 T" F* C/ y% X0 U! @9 xthe 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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