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

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DSH 201A   U7 Y2 e0 K- x, A , A+ }4 V9 e4 u8 A

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

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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:
$ i3 m2 _( [( `/ ?; w6 S. b) f% w" }$ |( d- Voltage drop
! |+ q& ~2 g9 ?+ N9 K! xThe maximum voltage drop which should not be exceeded, when passing from noload
to load condition, is 5% of the rated voltage.
" Z& M) X; f* j7 m/ T/ V$ k2 V: |- Voltage ripple value
The supply voltage ripple, at no-load condition, should not exceed 5%.
! z6 I8 a4 J% j- r1 L& 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.
/ q  K5 c$ ]  m& M- 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;
- Li is equivalent to the different self-inductances of the supply as well as the stray inductances of the rest of the test circuit;
" }" a! t7 ]" \* L- Cp is the stray capacitance of the circuit;
9 K2 g  H8 U3 \5 r8 v: n# D$ M- Rp is the parallel damping resistance.
( s% r8 x+ \  oNeglecting the parallel damping resistor, Rp, the parameters Li and Cp should be adjusted so as to obtain:
1 r# d& \+ _  X" {4 \( i( C. Q- Li = 2·10-3 H ± 25%, and
3 j: u; l' C& ?- 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.
, X3 J! x* v) Q, ~
+ u  G* r7 K6 v! x; n. l7 F7 j: ~

& u2 @% L/ b3 L1 I" [+ M, @8 |