Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Reexamination Certificate
1999-05-07
2001-04-24
Sherry, Michael J. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
C361S087000, C361S092000, C361S093600, C361S187000
Reexamination Certificate
active
06222713
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a protective switch with overcurrent and undervoltage functions for devices connectable to the usual AC mains with e.g. 230V/400V mains voltage, with the protective switch comprising a mechanical switching contact for a conductor, a latchable switch latch for the switching contact, an overcurrent sensor associated with the conductor and an electromechanical undervoltage relay whose exciting voltage is derived from the conductor voltage.
The protective switch can be of one-pole construction but it is preferably of multi-pole construction, in particular 3-pole construction. In this case, depending on the number of poles, several individual conductors to be monitored for overcurrent as well as a switching contact for each conductor are present. By contrast, a single common switch latch is sufficient in this case too, for operating all existing switching contacts.
The invention also relates to a overcurrent sensor as it is preferably and advantageously used in connection with a protective equipment switch of the type mentioned above.
STATE OF THE ART
Protective equipment switches of the type mentioned above are known in various designs. Traditionally a bimetal is used as an overcurrent sensor and the undervoltage relay is often integrated into the undervoltage relay in a separate unit.
With regard to the generic protective equipment switches there is the constant requirement of making them more economical, with a determining factor, apart from simple construction made of the smallest number of components possible, increasingly being the ability of fully automatic production or assembly if at all possible, and with the requirement for efficient calibration.
SUMMARY OF THE INVENTION
The protective equipment switch according to the invention comprises a mechanical switching contact for a conductor, a latchable switch latch for the switching contact, an overcurrent sensor associated with the conductor, and an electromechanical undervoltage relay whose exciting voltage is derived from the conductor voltage, with the overcurrent sensor in the case of overcurrent causing separation of the undervoltage relay from its exciting voltage, and with the release of the undervoltage relay causing unlatching of the switch latch.
When compared with known designs, the protective equipment switch according to the invention inter alia is characterised in that both in the case of overcurrent and undercurrent, unlatching of the switch latch is caused by the same component, namely the undervoltage relay. In the case of undervoltage, the undervoltage relay loses its excitement in the usual way and releases; in the case of overcurrent, excitement of the undervoltage relay is actively interrupted by the overcurrent sensor.
Preferably the undervoltage relay is directly able to unlatch the switch latch in that its armature is directly configured as a latch or latch lever for the switch latch.
By using the undervoltage relay as an active element for unlatching the switch latch, instead of the usual bimetal, mechanically fixed elements can be used to advantage for constructing the overcurrent sensor, with the overcurrent sensor preferably being constructed by combining a current transformer with an electronic circuit.
Such an overcurrent sensor which also forms part of the present invention.
By means of the current transformer signal according to a specified characteristic (e.g. one which approaches that of a bimetal generally comprising a 1/x or a hyperbola characteristic of time against the current) the electronic circuitry causes the mentioned separation of the undervoltage relay from its exciting voltage. In this connection it is of further advantage if the electronic circuit is an integrated circuit in the form of a so-called application specific integrated circuit (ASIC).
A particularly simple current transformer results from a pair of inductive loops on both sides of a section of the conductor on a printed circuit board, with, for the purpose of forming an iron core for the current transformer, a pair of iron core halves facing each other can be provided, one half on each side of the printed circuit board. The printed circuit board can at the same time also be used as a carrier for the electronic circuit.
By using a transformer, the voltage supply for the electronic circuit can be from the conductor, with, at least if the electronic circuit is designed as an ASIC, additionally a rectifier being required. As is the case with the ASIC, the voltage transformer as well as the rectifier can be installed on the mentioned printed circuit board and like the ASIC, it can be completely or only partly integrated.
Preferably, in the electronic circuit, the exciting voltage for the undervoltage relay is also derived from the transformed voltage. The said undervoltage relay can then be controlled directly by the electronic circuit and in particular if the said electronic circuit is an ASIC, it can be designed in a very small and compact way due to the low voltage level (typically 5 V).
Further preferred embodiments and advantages of the invention are disclosed in the following description of an embodiment, with reference to the enclosed drawings.
REFERENCES:
patent: 4013926 (1977-03-01), Lang et al.
patent: 4016518 (1977-04-01), Lang et al.
patent: 4025823 (1977-05-01), Lang et al.
patent: 4706158 (1987-11-01), Todaro et al.
patent: 4833563 (1989-05-01), Russell
patent: 4890184 (1989-12-01), Russell
patent: 5450048 (1995-09-01), Leger et al.
patent: 1 212419 (1970-11-01), None
Morgan & Lewis & Bockius, LLP
Schurter AG
Sherry Michael J.
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