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

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DSH 201A & O, d5 P3 L. X3 X0 C; f2 a

Characteristics of D.C. electric circuits for verifying normal operation and making and breaking cap ... 1 x# S% }( Y4 {

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Generality

% S# P5 l' I, E# Z# DTo 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
5 |' n) Z* D- f. \6 T3 Y5 K# cto load condition, is 5% of the rated voltage.
- Voltage ripple value
The supply voltage ripple, at no-load condition, should not exceed 5%.
  u6 m# {7 t8 B( n5 `/ Q5 _3 z' W0 [NOTES:
' Q  n' I2 b. h8 Y% B8 i6 O1 W" \- 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.
# _) Q* `+ ~) P- The use of a three-phase rectifying bridge, which gives a theoretical ripple of about 4,2%, complies with this recommendation.
- Recovery voltage
Test circuit, where:
- E is the supply voltage at no-load condition;
0 ^( S0 E2 _/ g1 {) n4 V$ @- Li is equivalent to the different self-inductances of the supply as well as the stray inductances of the rest of the test circuit;
( x0 ]3 L& D+ N8 q- 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
- y, E9 L0 U+ q- Cp = 50 mF ± 25%.
' m/ c$ A, _6 y9 k; `( \3 i5 vNOTE - Adopting the above mentioned parameters, all CTL Laboratories will get approximately
6 K, ^" l2 J8 |+ ]; a2 ]2 Z8 e2 e- 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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