DSH 201A Characteristics of D.C. electric circuits for verifying normal operatio

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DSH 201A & W, t" c( v# w6 ^3 w8 u% f9 o

Characteristics of D.C. electric circuits for verifying normal operation and making and breaking cap ... ! E/ I. u  M6 x+ y/ Q" j

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Generality 6 Y( t% Y3 I' R9 v3 s  t0 `3 Z% T

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:
6 A# ^* [& B2 Z& m( }* P- `5 n: c- Voltage drop
) e6 u" K! q7 x2 BThe maximum voltage drop which should not be exceeded, when passing from noload
! O7 X2 V! \- l. I; U( @to load condition, is 5% of the rated voltage.
) d7 ~: ~: t) J+ c$ V" U" A! u- Voltage ripple value
- }8 W! D, ?, n2 dThe supply voltage ripple, at no-load condition, should not exceed 5%.
( h! D$ a/ P( V1 y6 XNOTES:
6 u% c4 d+ V# W+ D- 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.
; }' a' x: C8 X! jA 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.
- The limitation of the ripple, which occurs, in practise, in rectifying converters, may be obtained choosing appropriately a rectifying bridge.
* h2 G' L8 X; S. S, `1 t6 y- The use of a three-phase rectifying bridge, which gives a theoretical ripple of about 4,2%, complies with this recommendation.
$ G/ D& H5 x0 o- M' c- Recovery voltage
Test circuit, where:
- E is the supply voltage at no-load condition;
. j# e5 r9 k8 ]6 o2 C8 m- Li is equivalent to the different self-inductances of the supply as well as the stray inductances of the rest of the test circuit;
- Cp is the stray capacitance of the circuit;
- Rp is the parallel damping resistance.
Neglecting the parallel damping resistor, Rp, the parameters Li and Cp should be adjusted so as to obtain:
- Li = 2·10-3 H ± 25%, and
8 M' o1 s/ @  B- f) X- Cp = 50 mF ± 25%.
3 }& {1 {2 T4 [$ Y) _7 f! BNOTE - Adopting the above mentioned parameters, all CTL Laboratories will get approximately
0 c' w! ~- g3 L- the same time constant T = Li / Ri = 2·10-3 / Ri;
  X% U8 [' j" P7 K; ^) l7 E0 h- the same oscillatory frequency fo = 1 / 2· (Li Cp)1/2  500 Hz.

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