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

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DSH 201A 1 V) N0 ^9 z) p9 `. n2 \ 1 v8 S- s; p* K2 ?' {% ^

Characteristics of D.C. electric circuits for verifying normal operation and making and breaking cap ... ; l$ [1 ^. s0 O+ r/ E2 g2 J; S; U

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Generality

9 C' Y* j& Q9 l4 ~! x( I2 k2 O3 [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:
! C5 ?9 }+ `5 y8 k8 q6 O- Voltage drop
7 l0 |& c3 J, l1 Z$ @; l$ F) S! mThe maximum voltage drop which should not be exceeded, when passing from noload
to load condition, is 5% of the rated voltage.
- Voltage ripple value
The supply voltage ripple, at no-load condition, should not exceed 5%.
NOTES:
- 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.
9 d8 G6 }' c7 Q( ~: ZA 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.
5 b  S* E& i& F2 H: K0 c7 f+ l+ _- The use of a three-phase rectifying bridge, which gives a theoretical ripple of about 4,2%, complies with this recommendation.
1 A5 n8 ~3 \0 s9 J- p4 m- Recovery voltage
& a" `% l9 B$ l. h- O, \! \Test circuit, where:
- 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;
+ m- Z7 _% E( ?) e; Z9 g! i, H% m2 ^- Cp is the stray capacitance of the circuit;
- Rp is the parallel damping resistance.
9 l, {# E. j! DNeglecting the parallel damping resistor, Rp, the parameters Li and Cp should be adjusted so as to obtain:
- Li = 2·10-3 H ± 25%, and
* Q$ A' A: R. o7 o- Cp = 50 mF ± 25%.
NOTE - Adopting the above mentioned parameters, all CTL Laboratories will get approximately
- the same time constant T = Li / Ri = 2·10-3 / Ri;
- the same oscillatory frequency fo = 1 / 2· (Li Cp)1/2  500 Hz.
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