Yamada Electric Mfg. Co., Ltd.

Yamada Electric Manufacturing Company Ltd.

Masahiko Niino

Kazuo Ito

Tomoyuki Ito

A bimetal 40 is secured at a holding portion 40b to a fixed pin 52 and a snap portion 40a is supported by a support portion 12a. The free end 40a' of the snap portion 40a comes in contact with a movable contact plate 30 to thereby rock the plate 30. The displacement of the snap portion 40a is restricted at a boundary end portion 40a' by the holding portion 40b. Due to this, when the thermal protector carries out a snap action (or is reversed), the snap portion 40a is rocked like a lever around the support portion 12a supporting the snap portion 40a, and the free end 40a' of the snap portion 40a is greatly displaced. Thus, the travelling distance by which the movable contact 32 travels when the movable contact plate 30 is rocked, can be increased. This can prevent a delay in snap.

Thermal protector

A motor protector includes a case having an open end, a terminal plate secured to the case and having a pair of fixed contacts, a disc-shaped bimetal supported in the case and having a pair of movable contacts engaged with and disengaged from the fixed contacts respectively, a temperature-sensitive switch disposed so as to close the open end of the case and sensing the temperature of a sensed object to be turned on when the temperature thereof reaches a predetermined value, and a heater disposed in the vicinity of the bimetal and connected in series to the temperature-sensitive switch.

Motor protector

A protective thermal relay comprises a main heater for heating a snap-action element of a bimetallic switch to open the switch. The main heater is connected in series with the motor or other device to be protected by the relay. There is also an auxiliary heater for the bimetal element that is energized through an abnormal condition detection relay, e.g., a negative phase sequence detector, when the abnormal condition occurs. The auxiliary heater is a positive temperature coefficient type and will heat and hold the switch in the motor off mode as long as the negative phase sequence or other abnormal situation remains.

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Nagoya, Japan

Masahiko Niino