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

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DSH 201A ; A$ r/ f: w  f5 e  h" T# _+ | / Q+ |" l- {. V9 s7 [  U

Characteristics of D.C. electric circuits for verifying normal operation and making and breaking cap ... 2 @1 T/ m) R# m+ N9 _: L( _3 |

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Generality

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:
- Voltage drop
7 K/ r1 f" g6 u- h7 U, nThe maximum voltage drop which should not be exceeded, when passing from noload
( S6 ~  }; m7 O- b/ Vto load condition, is 5% of the rated voltage.
, x5 S" c- ^( I- Voltage ripple value
5 k5 R5 f. n$ AThe supply voltage ripple, at no-load condition, should not exceed 5%.
! M! u' o' H6 w1 Q/ ?4 r0 sNOTES:
- 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.
4 P) M; _$ W' i( p) W- The use of a three-phase rectifying bridge, which gives a theoretical ripple of about 4,2%, complies with this recommendation.
2 l' {1 V8 z; e+ x: V# j$ q- Recovery voltage
Test circuit, where:
+ x, |! _4 y! ]3 u. Y- E is the supply voltage at no-load condition;
" _& n" d2 {! \- 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;
- |$ r* H0 D# v8 x* ?" n' u) _& [- Rp is the parallel damping resistance.
Neglecting the parallel damping resistor, Rp, the parameters Li and Cp should be adjusted so as to obtain:
! e3 H" Y# q& ?6 z6 x4 x& \) I" _- Li = 2·10-3 H ± 25%, and
) }0 m9 t2 M+ L, d- Cp = 50 mF ± 25%.
NOTE - Adopting the above mentioned parameters, all CTL Laboratories will get approximately
$ @5 C2 ~! U0 d9 v- 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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) Q& x, x/ Q8 R% h6 q" q1 k