Electrical transmission or interconnection systems – Switching systems – Condition responsive
Patent
1999-06-17
2000-12-05
Jackson, Stephen W.
Electrical transmission or interconnection systems
Switching systems
Condition responsive
323908, H01H 8320
Patent
active
061570974
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for protecting a resistor, for preventing a rush current in turning on a power source, of a power source apparatus having a capacitor input type rectification circuit.
BACKGROUND OF ARTS
Conventionally, as shown in FIG. 8, a power source apparatus consisting of a capacitor input type rectification circuit is provided with a resistor 3 for preventing a rush current before a smoothing capacitor 4, in order to prevent a rush current in turning on the power source, and is composed so that the resistor 3 for preventing a rush current is short-circuited by a relay 2, etc., after charging to the smoothing capacitor 4 is completed. In the same drawing, a rectification circuit is indicated by 1, a detection circuit for detecting making or breaking of the power source is indicated by 5, a calculation circuit using, for example, a microcomputer, is indicated by 6, and a relay drive circuit is indicated by 7. In addition, an alternate current power source is indicated by 10, and a contactor 11 is used to turn on and off the alternate current power source.
The alternate current power source 10 is made by the contactor 11, an electric current for charging the smoothing capacitor 4 flows via the resistor 3 for preventing a rush current. The relay 2 is provided so that, by short-circuiting the resistor 3 for preventing a rush current after charging of the smoothing capacitor is completed, voltage drop or power loss does not occur by an electric current flowing into the resistor 3 for preventing a rush current in usual operations of a power source apparatus.
When the alternate power source 10 is made, energy (E) charged in the smoothing capacitor 4 is given by the following expression: voltage [V] which is rectification-smoothed. Herein, where it is assumed that making and breaking are carried out N times in a certain time period t [sec.], at this time, the mean voltage P[W] can be expressed by the following expression (2).
Almost all of the power is consumed by the resistor 3 for preventing a rush current.
Therefore, if the alternate current power source 10 is frequently made and broken, there may be cases where the power P[W] expressed by the expression (2) exceeds a permissible power of the resistor 3 for preventing a rush current, and reaches a burn-out or interruption.
However, since there is usually a method for using the power capacitor (W) of the resistor 3 for preventing a rush current in only a limited period of closing the power source, there are many cases where the power capacity is small although the overload capacity is high. Therefore, if the power source is frequently turned on and off, the temperature rise becomes high, whereby there causes a problem by which the resistor 3 for preventing a rush current is burnt out or interrupted.
Accordingly, it is an object of the invention to prevent in advance a resistor for limiting a rush current into a smoothing capacitor of a power source apparatus having a capacitor input type rectification circuit, from being burnt out or interrupted.
DISCLOSURE OF THE INVENTION
The invention is featured in that energy is calculated, which is charged from a smoothing capacitor in making the power source from the capacity of a smoothing capacitor of a capacitor input type rectification circuit and a value of rectification smoothing direct current voltage; mean power is calculated from the above energy and the number of times of making and breaking the power source, which have been carried out in a determined period of time; and a warning is issued by alarm indication or alarm output where the mean power exceeds a permissible power of a resistor for preventing a rush current in making the power source, wherein an interlock is secured so that the power source cannot be made, or a load side apparatus is stopped so as not to drive.
If the capacity of a smoothing capacitor and the value of a rectification smoothing direct current voltage are known in advance, the number of times of making and breaking the power source,
Hirose Kenji
Ono Akihisa
Jackson Stephen W.
Kabushiki Kaisha Yaskawa Denki
Roberto Rios
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