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|  DSH 201A; R$ I7 z& Q9 q" P, L# y% [% W
1 w; f. ]/ Q8 l6 Z | Characteristics of D.C. electric circuits for verifying normal operation and making and breaking cap ...
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| Generality
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To 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:) m' i- V# m8 A- p7 T
- Voltage drop
; b! i6 H2 k9 ~The maximum voltage drop which should not be exceeded, when passing from noload
# m& N" f& A3 Fto load condition, is 5% of the rated voltage.
% }3 x$ x* T2 T+ j* f- Voltage ripple value
8 H' j# r5 M, @, z! y- JThe supply voltage ripple, at no-load condition, should not exceed 5%.4 M |7 E. ^( \% E$ O1 W9 i4 }
NOTES:
6 I- l0 ~ ]5 z4 @3 D( j- 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.( `* E# T' {- @! w7 l5 |# e
A 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.
' V& U8 X) Y4 i- The limitation of the ripple, which occurs, in practise, in rectifying converters, may be obtained choosing appropriately a rectifying bridge.
5 o- X7 P$ A/ o" ^- The use of a three-phase rectifying bridge, which gives a theoretical ripple of about 4,2%, complies with this recommendation.( z& a7 g- l# X
- Recovery voltage
' @$ w0 }/ z) u# N. i1 u! P3 ^Test circuit, where:. E& j6 U# n5 q2 w6 L3 Z/ N
- E is the supply voltage at no-load condition;( w+ w' m6 j0 R, x# U
- Li is equivalent to the different self-inductances of the supply as well as the stray inductances of the rest of the test circuit;
7 x' {1 s1 V+ D! z- Cp is the stray capacitance of the circuit;
: `. N h! p e" M- Rp is the parallel damping resistance.
7 }- l; f( t$ x2 @% HNeglecting the parallel damping resistor, Rp, the parameters Li and Cp should be adjusted so as to obtain: m- B* U0 X2 g9 J& z; z: b4 q
- Li = 2·10-3 H ± 25%, and
# f1 l+ G0 y" y5 c) ?8 R- Cp = 50 mF ± 25%.+ ]; f4 q7 g2 R9 j- ^6 O6 `
NOTE - Adopting the above mentioned parameters, all CTL Laboratories will get approximately- [' W" L- Z5 I3 D) S2 g! v
- the same time constant T = Li / Ri = 2·10-3 / Ri;
( b4 @+ n$ L: j% r, R/ t' d- the same oscillatory frequency fo = 1 / 2· (Li Cp)1/2 500 Hz.& ? Z) }9 B$ f( \, o/ ]- h
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发表于 2012-9-5 11:26
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