Safety Requirements For The Electrical Part Of The Brake System

Due to the use of mechanical electric brakes, it is also very important to inspect the electrical components of the brakes.
(1) Under working voltage, operate the traction machine according to its operating mechanism, load duration, and cycle. When the brake reaches a thermal stable state, measure the temperature rise of the brake coil. The measurement method adopts the resistance method specified in Article 8.6.2 of GB 755-2008 "Rating and Performance of Rotating Electrical Machines" for measurement and calculation. When using B-level insulation, the temperature rise of the brake coil should not exceed 80K; When using Class F insulation, the temperature rise of the brake coil should not exceed 105K. For brakes with exposed surface temperatures exceeding 6 (TC), warning signs to prevent burns should be added.
(2) The withstand voltage test of the brake coil should meet the requirement of applying 1000V voltage between the conductive part and the ground for 1 minute, and there should be no breakdown phenomenon.
(3) The minimum suction voltage and maximum release voltage of the brake solenoid should be measured after the brake temperature rise test is completed. GB/T 24478-2009 "Elevator Traction Machine" stipulates that the minimum suction voltage and maximum release voltage of the brake solenoid should be lower than 80% and 55% of the rated voltage, respectively.
(4) Newer brakes are equipped with a brake monitoring switch. When the brake operates abnormally, the switch will activate and the elevator will stop for protection, providing a guarantee for the safe and reliable operation of the brake. But there are no relevant standard requirements, and I hope they will be reflected in the standards in the future for maintenance and inspection.
(5) Another key point of the brake electrical part is the control circuit of the brake coil. According to relevant standards, it can be summarized as follows: ① During normal operation, the brake should remain in a released state under continuous power supply. ② To cut off the brake current, at least two independent electrical devices should be used, regardless of whether these devices are integrated with the electrical device used to cut off the current of the elevator drive host. ③ The so-called independence refers to the absence of mutual control relationship between two contactors, which must be controlled by two independent signals and cannot be controlled by one signal When the elevator stops, if the main contact of one of the contactors is not open, the elevator should be prevented from running again at the latest when the next direction of operation changes When the elevator motor has the potential to generate electricity from the generator, it should be prevented from feeding power to the electrical device that controls the brake. ⑥ After disconnecting the brake release circuit, the elevator should be effectively braked without any additional delay. The braking response time of the brake should not exceed 0.5 seconds to prevent the elevator from pulling backwards or slipping. The response time of the working brake, which also serves as a braking element for the up speed protection device of the elevator car, should comply with the braking requirements of Article 9.10.1 of GB 7588-2003 If one contact in the circuit is stuck, the other contactor contact can still reliably disconnect the brake circuit to prevent slipping Can monitor the fault of contactor not opening to prevent another contactor not opening and causing a slide.