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

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DSH 201A , u& f8 B) s5 U9 C1 H

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

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Generality

" ~$ O% I1 h! F& W) s' tTo 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:
7 D/ ~  B! ^9 \9 \* r7 e2 N- Voltage drop
: Z' V  M8 W, n7 a# j/ S' pThe maximum voltage drop which should not be exceeded, when passing from noload
to load condition, is 5% of the rated voltage.
. y  H2 `  [! X- s& m8 \) A9 D- Voltage ripple value
The supply voltage ripple, at no-load condition, should not exceed 5%.
NOTES:
7 ~$ N7 \8 H/ K4 g1 X% s- 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.
: R% }, t5 ?: C% J8 i9 D- vA 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.
# I! P) F6 o9 n2 l7 q# ]- 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
Test circuit, where:
5 U# }/ d) D" E. y. k* i/ F& h! h- 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;
- Cp is the stray capacitance of the circuit;
6 b4 n2 n2 p5 Q- Rp is the parallel damping resistance.
; O% j( i  Q1 B% c/ ^# v2 L- lNeglecting the parallel damping resistor, Rp, the parameters Li and Cp should be adjusted so as to obtain:
' Q. V) L1 S# H1 q8 T, R& u- Li = 2·10-3 H ± 25%, and
6 z( |! Q1 g: M  s- Cp = 50 mF ± 25%.
NOTE - Adopting the above mentioned parameters, all CTL Laboratories will get approximately
8 F, W$ S* U; {- the same time constant T = Li / Ri = 2·10-3 / Ri;
: H) }, G9 y+ P! C" [, g- the same oscillatory frequency fo = 1 / 2· (Li Cp)1/2  500 Hz.
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  v# ?  W) T) Z

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