Brake resistance protection circuit and method of frequency converter [Invention]

This method and circuit can effectively avoid the risk of fire in the control cabinet caused by the burnout of the brake resistance caused by the current flowing through the brake resistance due to the failure of the brake unit and the long-term heating of the brake resistance.

Elevator gantry Crane Control Method [Invention]

The invention discloses an elevator gantry crane control method, which enables the elevator door to close at a given speed by detecting whether the command signal of the switch door conveys normally and giving a preset speed to the speed ring when the command signal of the switch door is lost, thus preventing the clamping accident of the elevator door from being quickly closed by an external mechanical device.

The patented technology solves the problem of clamping elevator door crane in case of abnormal door command or power failure.

Elevator control method and system based on position identification of lower forced switch [Invention]

Elevator control method and system based on position recognition of forced lower switch learn the installation position of forced lower switch in advance and judge whether the elevator is running at normal speed and position according to the learned installation position.If abnormal, control elevator to decelerate.When the elevator is detected passing through the second and first panels in turn during deceleration, the current floor is initialised as the second and first floors, respectively.The operation of the elevator is controlled according to the initialized floor information.If the elevator is powered up again after power failure, it is necessary to judge the signal of the downward forced switch and whether the elevator is flat or not.Restore the current floor information according to the judgment results.

Therefore, the elevator can be controlled according to the initial floor information and the restored floor information without using non-standard form or additional setting of PLC, which makes the elevator control system more convenient.

The patented algorithm automatically identifies the installation position of the forced switch under the elevator and reduces the requirement that the forced switch under the elevator must be installed below the second floor.With this technology, the forced switch under the elevator can be installed above the second floor, which brings great construction benefits for some occasions where the size of elevator shaft is limited.