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

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DSH 201A . G: p8 Z0 R) U$ X8 I8 e, U2 l

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

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Generality / v9 z3 E: s. o0 w3 _% K; x

8 |9 r3 S' {& v2 _  jTo 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:
- Voltage drop
The maximum voltage drop which should not be exceeded, when passing from noload
7 K. }: f' g3 a& c) Z' u4 ~8 Zto load condition, is 5% of the rated voltage.
- Voltage ripple value
2 h& B( M  y9 [" Y) |3 vThe supply voltage ripple, at no-load condition, should not exceed 5%.
* C+ k0 A" u9 C6 Y. Y8 @# XNOTES:
& H0 b5 o( T0 v( B; b- ?  F8 N0 ~# 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 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.
: S( j3 I& d8 [; ?  V- The use of a three-phase rectifying bridge, which gives a theoretical ripple of about 4,2%, complies with this recommendation.
& u5 x2 ^4 C& U- A- Recovery voltage
- C3 b- L2 O1 {5 ?Test circuit, where:
- E is the supply voltage at no-load condition;
) [2 L9 L7 }: V2 |* P( ~3 B9 o- Li is equivalent to the different self-inductances of the supply as well as the stray inductances of the rest of the test circuit;
4 h- u1 J5 U$ d1 R. O3 r( p- Cp is the stray capacitance of the circuit;
: `* I% \6 W% B# i% z9 U5 ~8 s' |- Rp is the parallel damping resistance.
) [" u, i8 F; f! R$ \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
- Cp = 50 mF ± 25%.
( m- ^$ B' A1 B" a7 N. [) P. CNOTE - 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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