| CPC H01H 47/36 (2013.01) [H01H 47/002 (2013.01)] | 12 Claims |
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1. An electromagnetic contactor comprising:
a first contact;
a second contact;
a mechanism to generate a biasing force for opening the first and second contacts;
an operation coil to generate an electromagnetic force for bringing the first and second contacts into contact with each other against the biasing force; and
a coil drive device to supply current for generating the electromagnetic force to the operation coil,
the coil drive device including
a rectifier to output, to a power supply line, an input voltage obtained by full-wave rectification of an AC voltage supplied from an AC power source,
a switching element connected to the power supply line in series with the operation coil,
a voltage detector to detect the input voltage, and
a controller to control on and off of the switching element, wherein
the controller controls on and off of the switching element so as to control a duty ratio that is a ratio of an on period of the switching element in a switching period shorter than one cycle of the AC voltage, and controls the duty ratio in accordance with a value of a first parameter indicating a magnitude of the input voltage that is calculated using a detected value of the voltage detector, in at least a partial period after start of energization of the operation coil in response to a close command for the electromagnetic contactor, and
when a calculation value of the first parameter is larger than a predetermined reference value, the duty ratio is set to a value lower than when the calculation value is equal to or smaller than the reference value, wherein the reference value is set to a value of the first parameter corresponding to a nominal value of the AC voltage, and
when the calculation value of the first parameter is larger than the reference value, the controller sets the duty ratio in accordance with a value obtained by dividing the reference value by the calculation value.
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