Short circuit protection: the main power supply circuit is equipped with automatic air switch as the short circuit protection of crane; the control circuit is set with small capacity automatic air switch as short circuit protection.
Loss of voltage protection: the circuit structure has the function of voltage loss protection. When the power supply is restored after power failure, the crane can only run again by pressing the start button again, thus eliminating the possibility of self operation when the crane is powered on.
Emergency power-off switch: the crane is equipped with a red mushroom head rotary reset emergency power-off switch, which is used to quickly cut off the main power supply and control circuit of the crane in emergency. The emergency power-off switch shall be installed at a place convenient for personnel to operate.
Overload limiter: when the load reaches 90% of the rated lifting capacity, it will send out a prompt alarm signal. When the load reaches 110% of the rated lifting capacity, it will immediately cut off the lifting power supply and send out a prohibitive alarm signal. The sensor of overload limiter has the characteristics of moisture-proof and anti-seismic. The sensor is connected with the control box to reduce the interference of sensor signal.
Travel switch: the lifting mechanism is equipped with ascending and descending fire break limiters. As the limit switch of lifting mechanism lifting range, it also has the protection function against the adhesion of the controller; the crane mechanism is equipped with operation limit limiter, which is composed of travel limit switch and safety ruler. The travel limit switch is installed on the crane, and the safety ruler is installed on the rail bearing beam or wall where the crane is running, the crane can be operated within the safe range; the crane limit limiter can be either an ordinary limit switch or a photoelectric switch or a laser anti-collision device with higher performance, smaller volume and more accurate limit distance.
Zero position and interlock protection: air operated crane has zero position protection and interlock protection function of door switch. The zero position protection function prevents the occurrence of motor automatic operation when the crane recovers power supply after power failure and prevents accidents. The interlock of door switch can avoid the occurrence of people or objects falling from the door because the safety door on the crane is not closed and the cart suddenly runs.
Protection of phase failure, phase staggering, over-voltage and under-voltage: the integrated protector in the crane circuit system has the protection functions of phase failure, phase staggering, over-voltage and under-voltage. When the above four situations occur, the general power supply of the crane will be automatically cut off to prevent personal injury and equipment damage.
Grounding protection: the metal mechanism of crane and all electrical equipment metal shell, pipe groove and low voltage side of transformer are provided with reliable grounding, and the total grounding resistance is less than or equal to 4 Ω, and the crane rail is allowed to be used as the grounding wire. The insulation resistance of crane to ground at normal temperature shall not be less than 1m Ω (this value is the measured value of 500V meg-ohmmeter at room temperature).