Abstract A safety device includes a resistance, a condenser and a relay winding which are star-connected across a three-phase source of AC potential providing the supply potential for a three-phase motor which is controlled, as to operation in the normal and reverse directions, by a three-phase magnetic contactor connected to the motor by forward or normal and reverse end limit switches. The safety device further includes a normally closed contact which is opened upon energization of the relay winding, and this contact is connected in series in the control circuit of the electromagnetic contactor. This control circuit is connected to the same single phase as is the series connection of the condenser and the relay winding. If the three-phase source of AC potential does not have the proper phase sequence, or if a single phase is inoperative, the relay winding is sufficiently energized to open the normally closed contact and thus interrupt energization of the magnetic contactor with resultant deenergization of the three-phase motor driving the winch.
Inventors
👤 S Ishikawa
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-28 06:03
CPC Classifications
H; H02; H02H; H02H11/00; H02H11/004
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
142 words
A safety device, for a three-phase motor operating a winch and connected to a three-phase source of A.C. potential through a motor reversing magnetic contactor in series with forward and reverse end limit switches, the magnetic contactor having forward and reverse operating windiNgs in a series control circuit energized from a single phase of such source of A.C. potential, said safety device comprising, in combination, a resistance, a condenser and a relay winding star-connected to each other and to said source with said relay winding being connected across said single phase; and a normally closed relay contact controlled by said relay winding and connected in said control circuit in series with said operating windings; said relay winding being energized to open said normally closed relay contact responsive to a phase reversal of said source or failure of a phase of said source.
Claim 2
Dependent Claim
142 words
A safety device, for a three-phase motor operating a winch and connected to a three-phase source of A.C. potential through a motor reversing magnetic contactor in series with forward and reverse end limit switches, the magnetic contactor having forward and reverse operating windiNgs in a series control circuit energized from a single phase of such source of A.C. potential, said safety device comprising, in combination, a resistance, a condenser and a relay winding star-connected to each other and to said source with said relay winding being connected across said single phase; and a normally closed relay contact controlled by said relay winding and connected in said control circuit in series with said operating windings; said relay winding being energized to open said normally closed relay contact responsive to a phase reversal of said source or failure of a phase of said source.
Claim 3
Dependent Claim
73 words
A safety device for a three-phase AC motor, as claimed in claim 1, including first, second and third conductors connected to respective terminals of said three-phase source; said resistance, condenser and relay winding having first ends connected to each other; the second ends of said condenser, said relay winding and said resistance being connected to said first, second and third conductors, respectively; said control circuit being connected to said first and second conductors.
Claim 4
Dependent Claim
43 words
A safety device for a three-phase AC motor, as claimed in claim 1, in which said operating windings are connected in parallel with each other in said series control circuit, and each in series with a respective manually operable normally open push button.