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5.12 For heating appliances and combined appliances, when it is specified that the
. Y7 h0 U" h# g3 H1 c2 P+ l- mappliance has to operate at a power input multiplied by a factor, this applies only to heating+ D, C; m2 {( E$ P0 w
elements without appreciable positive temperature coefficient of resistance.( u( W& q6 a+ `; m% K y
For heating elements with appreciable positive temperature coefficient of resistance, other than
& Z" \! e* [' S$ lPTC heating elements, the supply voltage is determined by supplying the appliance at rated# M" a* F: m9 A* \+ K4 a: T
voltage until the heating element reaches its operating temperature. The supply voltage is then- p, O+ Z/ T% Q4 L: [% G# H
Copyright International Electrotechnical Commission, U B& I! P1 X4 H0 x
rapidly increased to the value necessary to give the power input required for the relevant test,) n% y* x6 p6 u
this value of the supply voltage being maintained throughout the test.1 o+ g3 a' U. Z: v/ i0 O2 I
NOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input% ~( k8 S% M' ]. n y+ m" j
of the appliance in cold condition differs by more than 25 % from the power input at operating temperature.
7 z* z* G+ _4 m2 B5.13 The tests for appliances with PTC heating elements and for heating appliances and
& H* `2 Q+ \) G: j4 _7 g9 |1 {combined appliances where the heating elements are supplied via a switch mode power# u) _% [- l! ~! J7 N: W2 W' q
supply are carried out at a voltage corresponding to the specified power input.
' C. D; x, u- m- _When a power input greater than the rated power input is specified, the factor for multiplying3 a' j4 S3 s) k6 b$ f) ]
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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