Protection circuits
AssigneeSociete Chimique des Charbonnages S.A.
InventorThadee Domanski
Life of this patent
Estimating the term…
Abstract
A protection circuit is provided which incorporates a reed relay whose contacts form the circuit breaker of an electrical appliance. The winding of the reed relay is supplied with a rectified alternating current derived from a current transformer coupled to the supply line to the appliance. In order to avoid periods of zero current in the winding, the winding is also supplied with a rectified alternating current from a source which is out of phase with that supplying the supply line. Failure of the current on the line will cause the contacts to open. Preferably the relay has a set of self latching contacts to prevent re-energization of the winding once de-energized. A manually operable reset switch is provided in series with the self latching contacts.
Claims15
A protection circuit for protecting an electric appliance supplied through a power supply line, comprising
- a reed switch having a set of magnetizable contact members, a set of contacts, each contact being mounted on a respective one of the contact members, a capsule housing the contact members and the set of contacts, and winding means supported by the capsule and energizable to produce a magnetic field for causing relative movement of the two contact members between first and second relative positioned settings,
- generating means coupled to the power supply line to generate a current in response to the current drawn by the appliance through the power supply line,
- first rectifying means electrically connected to the generating means for rectifying the generated current and supplying the rectified current to energize the winding means,
- means supplying a current out-of-phase with the current generated by the generating means, and
- second rectifying means connected to the current supply means to rectify the out-of-phase current and supplying the current to the winding means in a sense to produce a magnetic field assisting that produced by the generating means, whereby the composite magnetic field generated will maintain the set of contacts in the said first setting while the supply of both currents to the winding means is sustained but will switch the contacts to the second setting when the supply of one of said currents to the winding means fails.
A protection circuit for protecting an electrical appliance connected to a polyphase supply, comprising:
- means coupled to each phase of the polyphase supply to generate currents corresponding to the currents drawn by each phase of the polyphase supply,
- rectifying means connected to each generating means rectifying the current generated thereby, and
- a reed relay having a set of contacts connected as a circuit breaker for the appliance, and
- winding means connected to the rectifying means to receive the rectified currents, the rectified currents supplied to the winding means all assisting in the generation of a magnectic field to close the set of contacts whereby in the event of current failure in one or more phases of the supply, the magnetic field will drop sufficiently to allow the contacts to open and so break the circuit of the appliance, and
- wherein the winding means comprises one coil for each phase of the polyphase supply, each coil being connected to receive the current from a corresponding said rectifying means, and wherein the rectifying means comprises a diode connected in a series with each coil.
A protection circuit for protecting an electrical appliance connected to a polyphase supply in the event of a current failure in one or more phases of the polyphase supply, the circuit comprising:
- a relay switch having energizing winding means and a set of contacts connectable as a circuit breaker for the appliance and actuable in response to energization of the winding means,
- current transformer means coupled to each phase of the supply for detecting the presence of a current in each phase of the said supply,
- rectifying means connected to each current transformer means for rectifying the output of the current transformer means, and
- means feeding the currents from the rectifying means to the winding means in a sense to assist each other in producing a magnetic field for actuating the set of contacts, whereby the failure of current in at least one of the phases of the supply will cause at least a partial current failure in the winding means and therefore de-actuation of the contacts, and
- wherein the relay switch includes a second set of contacts connected by the feeding means in series with the winding means and the rectifying means, the second set of contacts constituting a self-latching set of contacts for the relay switch, whereby failure of current in at least one of the phases of the supply will interrupt the current path between the rectifying means and the winding means.
Dependencies are inferred from the claim text.