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5.12 For heating appliances and combined appliances, when it is specified that the
2 X3 O: g3 S; r$ d0 {% ^% L7 {appliance has to operate at a power input multiplied by a factor, this applies only to heating6 V3 O1 E# _" q7 ]) _5 h b
elements without appreciable positive temperature coefficient of resistance.( Z5 a& M- r2 @* [! A7 d! F$ E# C" n
For heating elements with appreciable positive temperature coefficient of resistance, other than \4 u1 P6 u+ q! y ] ?4 D
PTC heating elements, the supply voltage is determined by supplying the appliance at rated
( j1 k9 |$ R3 O9 L8 M* p# Tvoltage until the heating element reaches its operating temperature. The supply voltage is then
1 ~( m9 B7 M: K: h# v6 `6 v o9 ?Copyright International Electrotechnical Commission
: s2 Y2 Q- {. q* ]# ^rapidly increased to the value necessary to give the power input required for the relevant test,
' X3 D- F1 c7 ~6 v7 T% }this value of the supply voltage being maintained throughout the test.! ^9 |( e1 O6 c3 B. f6 q( N
NOTE In general, the temperature coefficient is considered to be appreciable if, at rated voltage, the power input
8 g0 D ]' G8 I4 Jof the appliance in cold condition differs by more than 25 % from the power input at operating temperature.# v N, Z/ t/ a
5.13 The tests for appliances with PTC heating elements and for heating appliances and8 |2 U' q( Y; V( N, c* W b
combined appliances where the heating elements are supplied via a switch mode power! B$ Y3 s5 v1 d/ ]; s- z
supply are carried out at a voltage corresponding to the specified power input.
3 Q2 l/ z. l% L. |# G. D, @When a power input greater than the rated power input is specified, the factor for multiplying
: u. e# r0 W) _% Q) fthe 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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