Briefly discuss the braking test of 125% rated load of elevator with star sealing function

When the elevator stops due to sudden power failure or failure, it is one of the most common rescue operations to release the elevator brake and move the car to the floor station by operating mechanical or electric devices, so as to safely rescue the trapped people in the elevator. After the brake is released, the car moves in three ways: (1) from slow to fast; (2) basically keep uniform movement; (3) Intermittent movement. If the elevator is equipped with the star sealing function, when the brake is continuously operated and released, the car can basically keep a uniform speed after moving. After the permanent magnet synchronous drive engine loses power, the function of “motor sealing star” can be short-connected to the three-phase terminal of the motor to generate electromagnetic torque opposite to the mechanical torque caused by the imbalance of the cage and the weight, so as to realize the elevator can be kept at a constant low speed when the brake completely fails. This technology reduces the rescue with the staff of wrong operation, such as continuous loose brake) or equipment failure (such as remote loose brake line card resistance cannot be reset, plunger type brake resistance of moving iron core in the process of closing CARDS) capsules in the header or Dun risk, to a certain extent, also reduce the risk by shearing the car accident caused by mobile workers (out of control of capsules from stop slip velocity is small, It increases the reaction time of passengers to avoid risks, as well as the closing time of the well entrance of the automatic horizontal sliding door driven by power), and improves the safety of the elevator.
When the brake works normally in the elevator, the function of zero-speed lock brake is to keep the car stationary after the elevator is flat; In the case of safety emergency stop, it is necessary to absorb the kinetic energy of the elevator movement system, so that the driving main engine stops running. In order to prevent the elevator header, Dun bottom, open the door slide, such as serious accident, need to fully guarantee the performance of the brake, so must be validated in the safety inspection brake braking performance. TSG T7001-2009 Elevator Supervision Inspection and Periodic Inspection Rules — Traction and Forced Drive Elevator (including Amendment No.1, 2 and 3), the inspection contents and requirements of item 8.11 “Traction Inspection under Downward Braking Conditions” and item 8.13 “Braking Test” are aimed at the inspection of the mechanical braking force of the brake.
The basic principle of PSM gearless traction machine star sealing technology is that when the power supply of PSM is disconnected, the stator windings of the motor are shorted and the permanent magnet of the traction machine rotor is rotated by the mechanical torque caused by the weight difference between the two sides of the traction wheel. The alternating magnetic field generated by the permanent magnet generates an induced current in the stator closed loop, and the electromagnetic torque generated by the current prevents the rotor permanent magnet from running, forming an electrical braking torque. If 125% braking test is carried out with the participation of star sealing braking, the driving engine stops running as a result of the combined action of mechanical braking of the brake and star sealing electromagnetic braking of the motor, which cannot truly reflect the mechanical braking ability of the brake. Therefore, in order to accurately verify the effectiveness of the brake test, when the elevator has the star sealing function, personnel should first cancel the star sealing function before the emergency stop test of the brake, and only the mechanical brake should be able to make the driving main engine stop running.
Descending braking test method for 125% rated load of elevator with motor sealing function
1.1 Personnel shall have safe and easy access to contactors with star sealing functions
The operation contactor is used to extend the auxiliary contact design, and the normally closed auxiliary contact group of contactor is the star sealing contact, which is widely adopted at present. Common testing methods are as follows.
(1) During the downward movement of the car with a uniform distribution of 125% of the rated load, personnel shall press and hold the star sealing contactor (forced pull) with appropriate tools (such as insulation rod and screwdriver) to keep the star sealing contact disconnected; When the car is running at normal speed to the lower stroke, cut off the power supply to the motor and brake.
(2) Check the stop condition of the driving main engine and cage. The driving main engine should stop running and the cage should stop completely.
(3) Release the star sealing contactor.
(4) Check the cage should have no obvious deformation and damage.
1.2 Contactors with star sealing functions cannot be safely and easily accessed by personnel
If the control cabinet is installed in the upper part of the well, it is dangerous for personnel to hold the star sealing contactor while standing on the top of the running sedan, then how to cancel the elevator star sealing function?
1.2.1 Improve the design and add external switch for star sealing operation
When the control cabinet is installed in the well path, the break point of the star sealing connection line can be connected to an additional switch ON the emergency operation and dynamic test device (can be called “star sealing switch”). The star sealing function is active state “ON” and the star sealing function is cancelled state “OFF”. The operation method of emergency operation and dynamic test device shall be specified in the Operation and Maintenance Manual.
1.2.2 Alternative test Method (Taking a brand elevator as an example)
TSG T7001-2009 Item 8.11 “Towing Check under Downward Braking Conditions” requires that the car should be completely stopped and the towing ability of the elevator and the mechanical braking ability of the brake should be evaluated. Item 8.13 “The brake shall be able to stop the driving main engine” mainly evaluates the mechanical braking ability of the brake.
The star sealing contactor of a certain brand elevator is welded to the internal circuit board of the drive. The coil and contact of the contactor are welded on the printing plate (not connected by wire), and the star sealing cannot be canceled by disconnecting the normally closed contact; This brand elevator brake electromagnet coil is divided into two assembly sets. The test method of 125% rated load braking test proposed in items 8.11 and 8.13 of TSG T7001-2009 can be replaced by the following two tests.
(1) If a group of brake mechanical components that apply braking force to the brake wheel (or disc) do not work, the group of components is always in a raised state. In order to make a group of brake components in the lift state, the electrical logic line of the elevator requires that the star sealing contactor is always in the suction state, that is, the star sealing loop is broken and the star sealing function does not work.
In the absence of Feng Xing, make any group of mechanical components of the brake ineffective respectively. When the car is loaded with rated load and goes down at the normal running speed, check the braking condition of other brake components and verify the 8.13 “braking test” of TSG T7001-2009. If any set of components does not work, the brake should still have enough braking force to slow down, stop and maintain the stopped state of the car with rated load going down at rated speed. After the test, the car should have no obvious deformation and damage.
(2) In the case of Feng Xing’s participation, the cage is loaded with 125% rated load. When descending at the normal running speed, the power supply of the motor and brake should be cut off. The cage should slow down, stop and keep stopped. In combination with the braking conditions in paragraph (1) above, item 8.11 of TSG T7001-2009 “Towing Check under Braking Conditions” is comprehensively verified.
If both of the above tests are qualified, item 8.11 and Item 8.13 will be judged to be qualified.
2. Demonstration of alternative test methods
(1) Illustrate the braking effect when a group of components do not work under rated load. A towed elevator with a rated load of 1 000kg has two sets of brake mechanical components (hereinafter referred to as two sets of brakes) applying braking force, and the balance coefficient is 0.40. The braking force required for passing the braking test of a single group of brakes is more than 600kg, and the braking force of two groups of brakes is more than 1 200kg. This is equivalent to the carriage carrying not less than 160% of the rated load and more than 125% of the rated load specified in this clause.
If a set of mechanical components of the brake does not work, the rest of the brake components still have enough braking force to slow down, stop and keep the car with rated load going down at rated speed. When the balance coefficient q is between 0.40 and 0.50, 2(1-q) > 1.25-q, it can be determined that the brake has enough braking force to slow down, stop and keep the cage with 125% rated load at the rated speed. That is to say, meet “all the brake mechanical parts involved in the application of braking force to the brake wheel or disc shall be divided into two assembly devices. If a set of components do not work, there should still be enough braking force to slow down the cage carrying the rated load at the rated speed “, must meet the “when the cage carrying 125% rated load and running down at the rated speed, the operation brake should be able to make the tractor stop running”.
(2) Under the condition that the star sealing function is in effect, when the car is loaded with 125% rated load and goes down at the normal running speed, and the power supply of the motor and brake is cut off, in addition to the mechanical braking torque of the brake, there is also the star sealing electrical braking torque from the motor. Due to the large braking torque under the combined action of brake and star sealing, the brake deceleration of the elevator may be too large, so the possibility of the traction rope slipping on the traction wheel is greatly increased. Under the combined action of brake mechanical braking and star sealing electrical braking, if the car can stop completely, it indicates that the towing ability is qualified, and it can be determined that the car loaded with 125% rated load at normal running speed can be stopped under emergency braking condition with the star sealing function cancelled.
3 Conclusion
The purpose of the 125% rated load braking tests in items 8.11 and 8.13 of TSG T7001-2009 is to assess the mechanical braking and towing capabilities of the elevator brakes. The first step of the alternative test scheme is to carry out 100% rated load braking test when any group of mechanical parts of the brake do not work under the condition of star sealing does not work; On the premise that the test is qualified, the second step test is continued, that is, the braking test of 125% rated load is carried out when the star sealing is effective. Assuming that the mechanical parts of the brake are installed with no more than 3 groups, the braking torque required by the 100% rated load braking test (when a group of mechanical parts of the brake does not work) is greater than the braking torque required by the 125% rated load braking test under the condition that the star sealing does not work; The brake deceleration of the elevator is greater when the star sealing is effective than when the star sealing is not effective. Therefore, the qualification criteria of the alternative test method are more demanding than the inspection rules. If the former test passes, the latter test must pass.