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

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DSH 201A 9 b. H# g- S& j7 N2 ]

Characteristics of D.C. electric circuits for verifying normal operation and making and breaking cap ...

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Generality 9 ?: p( Z. Z- I/ f/ Q/ g6 b

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:
% L; v3 P4 ?+ Q9 y- H- Voltage drop
The maximum voltage drop which should not be exceeded, when passing from noload
to load condition, is 5% of the rated voltage.
* ?( M2 v8 a& u3 X+ t% z8 P& ^- Voltage ripple value
+ `6 d8 Y) K* S2 rThe supply voltage ripple, at no-load condition, should not exceed 5%.
, s$ \$ L9 f2 X/ JNOTES:
- 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 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.
- The use of a three-phase rectifying bridge, which gives a theoretical ripple of about 4,2%, complies with this recommendation.
- Recovery voltage
3 T" n  W$ M' @# j8 W; RTest circuit, where:
9 P. s9 J9 a+ n% j- E is the supply voltage at no-load condition;
* i; O; P5 p, ^) z9 q; ]- Li is equivalent to the different self-inductances of the supply as well as the stray inductances of the rest of the test circuit;
% m$ K* T. J3 \8 f% r: X8 j- Cp is the stray capacitance of the circuit;
7 M. z* z$ ]% m0 S; l- Rp is the parallel damping resistance.
8 J0 a& `2 K- N+ g' m! o5 q- [Neglecting the parallel damping resistor, Rp, the parameters Li and Cp should be adjusted so as to obtain:
8 D- ?. \% z8 J( n) `8 T+ m- Li = 2·10-3 H ± 25%, and
; S" g' o; A9 M7 Y5 d- Cp = 50 mF ± 25%.
3 l4 z2 M# j( i' @( G3 w8 ?NOTE - Adopting the above mentioned parameters, all CTL Laboratories will get approximately
+ Y9 f" M& d0 I- the same time constant T = Li / Ri = 2·10-3 / Ri;
6 U: X7 X2 p0 W  e' e- the same oscillatory frequency fo = 1 / 2· (Li Cp)1/2  500 Hz.
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