Open-phase protection device for three-phase motor

Abstract

The invention provides an open-phase protection device for a three-phase motor. The open-phase protection device comprises a phase line A, a phase line B, a phase line C, an electromagnetic breaker DTA and an electromagnetic breaker DTB; the electromagnetic breaker DTA is arranged on the three phase lines, can connect or disconnect the phase lines A, B and C at the same time and partitions the phase lines A, B and C into front phase line bodies A,B and C and rear phase line bodies A,B and C, two terminals of the electromagnetic breaker DTA are connected with the front phase line body A and the front phase line body B through a branch I and a branch II respectively, a switch K1 is arranged on the branch I and the branch II and used for connecting and disconnecting the two lines, two terminals of the electromagnetic breaker DTB are simultaneously connected with the rear phase line body A and the rear phase line body B through a branch III and a branch IV respectively, a protective circuit is connected to the branch III or the branch IV in series, the protective circuit comprises a switch K2 and a relay J connected in parallel, the relay J is a relay for inducting whether a motor normally works or not, and trip protection action can be achieved for common open phase, special open phase, deliberate damage open phase and the like of the motor.

Description

technical field [0001] The invention relates to the field of electrical technology, in particular to a phase loss protection device for a three-phase motor. Background technique [0002] At present, for the phase loss protection device used for three-phase motors, the general method is to install a thermal relay on the live line for protection. The defect of this method is that the value set by the conventionally used thermal relay is too small, the trip is frequent, and it cannot be used normally. If the value is adjusted too large, there will be a delay in tripping when there is a phase loss, which will accelerate unnecessary aging and seriously affect the service life of the motor. Moreover, most of the phase loss protectors currently on the market need to pass through complex The parallel circuit realizes a phase loss protection for three phases, the structure is complicated, the cost is high, and it cannot protect some special phase loss. The phenomenon that two of the...

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Problems solved by technology

[0002] At present, for the phase loss protection device used for three-phase motors, the general method is to install a thermal relay on the live line for protection. The defect of this method is that the value set by the conventionally used thermal relay is too small, the trip is frequent, and it cannot be used normally. If the value is adjusted too large, there will be a delay in tripping when there is a phase loss, which will accelerate unnecessary aging and seriously affect the service life of the motor. Moreover, most of the phase loss protectors currently on the market need to pass through complex The parallel circuit realizes a phase loss protection for three phases, the structure is complicated, the cost is high, and it cannot protect some special phase loss. Phase fire wires, two of which are the same fire wire phenomenon, the general lack of phase protector cannot identify, at the same time, the trip protection cannot be realized for motor failures and other idling or useless work motors

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