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标题: DSH 201A Characteristics of D.C. electric circuits for verifying normal operatio [打印本页]
作者: 小米    时间: 2012-9-5 11:26
标题: DSH 201A Characteristics of D.C. electric circuits for verifying normal operatio
DSH 201A; O9 W" I# B& _6 ^/ g. m  t- \1 Z
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Characteristics of D.C. electric circuits for verifying normal operation and making and breaking cap ...
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! y. y! N1 h  s2 c0 S$ rTo reach an acceptable test reproducibility, when verifying normal operation and making and breaking capacity, it is recommended that the test circuit has the following characteristics:
1 V1 B9 v: j9 ]% N! l- Voltage drop
* Z8 m% Q! b" DThe maximum voltage drop which should not be exceeded, when passing from noload: _( s7 X3 i8 |, c8 H0 u' J
to load condition, is 5% of the rated voltage.
& Q: f! q( C- z) m/ K/ H' H- Voltage ripple value8 L  x" h0 m% R5 P
The supply voltage ripple, at no-load condition, should not exceed 5%., |  T. T1 b( B* d- e3 M; S5 ^
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- Percentage ripple is given by r% = Vac/Vdc x 100, where Vac is the RMS value of the superimposed a.c. voltage and Vdc is the d.c. voltage.
+ R9 H! _. j8 z1 eA simple way to evaluate the ripple is to use an oscilloscope, whose input is selected in a.c. for the measurement of Vac and in d.c. for the measurement of VDU.
- G. {( I4 ?" Z; y; X- The limitation of the ripple, which occurs, in practise, in rectifying converters, may be obtained choosing appropriately a rectifying bridge.
& n( y1 X/ W4 {' L9 ^- The use of a three-phase rectifying bridge, which gives a theoretical ripple of about 4,2%, complies with this recommendation.: V/ @$ n& c# `- U. r; A
- Recovery voltage
- f( @1 N2 N; O, u% lTest circuit, where:/ {: [, X7 X; A/ N
- E is the supply voltage at no-load condition;. J" m- K& F. z/ B6 L5 Z9 S4 ~
- Li is equivalent to the different self-inductances of the supply as well as the stray inductances of the rest of the test circuit;
3 V) p, V" g0 q5 l! `, Z7 d1 o1 X- Cp is the stray capacitance of the circuit;
2 G* P/ D3 u1 p9 n% ~- Rp is the parallel damping resistance.
' D2 K  M; o% S% S" L0 ANeglecting the parallel damping resistor, Rp, the parameters Li and Cp should be adjusted so as to obtain:
5 p! `, _3 n9 g/ h- Li = 2·10-3 H ± 25%, and( K, q+ }6 w8 @6 @
- Cp = 50 mF ± 25%.) z/ A( u" Q& _& }
NOTE - Adopting the above mentioned parameters, all CTL Laboratories will get approximately. c5 W6 g; x. ^' s9 a9 W
- the same time constant T = Li / Ri = 2·10-3 / Ri;
4 z+ s; o. j4 c6 T- the same oscillatory frequency fo = 1 / 2· (Li Cp)1/2  500 Hz.8 q2 R; ^2 ^; p1 \& x  [) a1 s
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