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

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DSH 201A

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

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Generality

7 T/ w6 Y; q5 g$ ?/ J0 PTo 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
2 X! G0 C5 G. EThe maximum voltage drop which should not be exceeded, when passing from noload
$ O1 E: T  R7 }9 g( D+ j$ B' Ito load condition, is 5% of the rated voltage.
- Voltage ripple value
The supply voltage ripple, at no-load condition, should not exceed 5%.
9 [9 a* B9 r1 ^/ E) A8 cNOTES:
) ~8 f& b* I) N9 v  m- 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.
- 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:
1 T8 [* f+ a. g8 s* I+ @; L1 b- E is the supply voltage at no-load condition;
$ C' t4 e. u0 ~7 z" Q8 R- c- Li is equivalent to the different self-inductances of the supply as well as the stray inductances of the rest of the test circuit;
' ]% _- T) d9 \6 i- Cp is the stray capacitance of the circuit;
9 w) R; C& Z8 d# ?; n- 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
# P* x7 y+ H& o  @, s3 x! b. w* J- Cp = 50 mF ± 25%.
7 [6 L9 i% b( m3 |; E. GNOTE - 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.



& l! x  H4 B$ J0 O) d9 X; _
& K3 a+ H2 W! c# `, o$ m3 H) F- x
5 s/ a8 N1 y( D* U& ?3 v' V