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

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DSH 201A

Characteristics of D.C. electric circuits for verifying normal operation and making and breaking cap ... / Q! D. `; c' l3 P+ I' _, d# r

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Generality

) |9 r" ?' e- d3 fTo 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:
8 ?/ n, P+ ]$ ~7 _5 J% ~0 D$ A+ A- Voltage drop
The maximum voltage drop which should not be exceeded, when passing from noload
* N: l, G. o) m9 H! Hto load condition, is 5% of the rated voltage.
- Voltage ripple value
; q0 J: q- U( _The supply voltage ripple, at no-load condition, should not exceed 5%.
4 t/ B/ T. p2 n' x& B7 b4 G! wNOTES:
0 `) }+ I' \! x! w$ F+ b2 ~- 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.
& k' s1 S  k, B* u- The use of a three-phase rectifying bridge, which gives a theoretical ripple of about 4,2%, complies with this recommendation.
- T0 H2 k/ R1 o+ Z- Recovery voltage
Test circuit, where:
, W) l+ V. Q3 g+ x/ T' p- E is the supply voltage at no-load condition;
- Li is equivalent to the different self-inductances of the supply as well as the stray inductances of the rest of the test circuit;
/ i9 ?8 ]8 ~' v- 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:
: C* I5 G2 [1 |- Li = 2·10-3 H ± 25%, and
- Cp = 50 mF ± 25%.
. c- |6 t# c) r, V* h  e# ^' e8 o. dNOTE - Adopting the above mentioned parameters, all CTL Laboratories will get approximately
) a) i& Y' V4 g# h- the same time constant T = Li / Ri = 2·10-3 / Ri;
- {! l# A3 V7 o6 D' M- the same oscillatory frequency fo = 1 / 2· (Li Cp)1/2  500 Hz.
1 [" A; R" O5 T& Y9 K7 Z
: w3 a( m  ?6 A( j# \
7 Y  x: v1 j4 A6 s" b# C
& |0 y1 F/ Y6 E
$ V0 N4 P8 s" b! C! W