Patent Application
20230007842
The invention relates to a method for testing an elevator hoisting machine brake and to a system for implementing the method. In general, the invention relates to ensuring sufficient braking effort of a hoisting machine brake.
Elevators have electromechanical hoisting machine brakes as safety devices to apply braking force to a traction sheave or a rotating axis of an elevator hoisting machine. There are normally at least two separate brake units, such as two, three or four units. They shall be dimensioned to stop and hold standstill an elevator car with an overload. If one brake unit fails, for safety reasons the remaining ones should still stop and hold an elevator car with suitable safety margin.
Due to their characteristics as elevator safety devices, operating condition of the hoisting machine brakes shall be confirmed.
One confirmation method is disclosed in EP 1915311 B1. According to the method, only one holding brake of the elevator hoisting machine is engaged at the end of elevator run, and motor torque is removed. If traction sheave starts moving due to the gravity effect, holding brake is considered defective.
There is a need for enhanced test methods, to get the brakes accurately tested in their entire operational range.
The object of the invention is to introduce a method which is capable of testing sufficiency the braking effect, particular the braking torque of an elevator hoisting machine brake, by using a test load with improved accuracy.
Advantageously the test load is established by complementing the load caused by elevator unbalance with an assisting motor torque of an elevator hoisting machine.
Assisting motor torque includes components selected to compensate against the unidealities of real-life elevator systems. Therefore, assisting motor torque provides for accurate testing of the hoisting machine brakes.
An object is to introduce a solution by which one or more of the above defined problems of prior art and/or drawbacks discussed or implied elsewhere in the description can be solved. An object is particularly to introduce a solution by which testing of hoisting machine brakes can be provided accurately and simply.
It is brought forward a new method for testing an elevator hoisting machine brake with a preselected test load TL, which method comprises:
Preferable further details of the method are introduced in the following.
According to some embodiments the method is repeated for each hoisting machine brake by keeping it open while keeping the rest of the brakes engaged in braking position.
According to some embodiments the test load TL corresponds to a preselected overload, which is represented by a factor OL as follows TL=OL*N, wherein N is a nominal load N of the elevator car, and preferably OL is selected from range 101% . . . 130%, more preferably 105% . . . 120%, most preferably OL=110%.
Preferably the elevator comprises:
an elevator car, a counterweight and elevator ropes arranged movably within a hoistway, wherein the elevator car and the counterweight are supported at least partially by means of the elevator ropes; and
a hoisting machine, which comprises
According to some embodiments measuring the movement of the elevator car is implemented by measuring rotation of the elevator hoisting machine, preferably measuring movement of the motor or the traction sheave connected to the motor and supporting the elevator ropes for moving the elevator car. The motion information of the elevator car for the drive unit may be obtained from a rotation sensor or a resolver connected to the motor or from a positioning device connected to the elevator car or located in the hoistway.
Preferably the hoisting machine motor is a synchronous permanent magnet motor.
It is also brought forward a new system for implementing the inventive method. The system may be a part of an elevator drive unit or provided separately. The system may be implemented in a hardware and/or software module of the elevator drive unit and/or in an elevator maintenance or installation tool to install or service the elevator.
According to an embodiment, the elevator drive unit comprises an elevator hoisting motor, preferably a synchronous permanent magnet motor, and a frequency converter configured to drive the motor.
According to some embodiments the system has an input for the motor current fed to the motor and an input for the car location, the inputs being connectable to the elevator drive unit.
In the following the present invention will be described in closer detail by way of example and with reference to the attached drawings, in which
The traction sheave 6 may be integrated to the motor 5 or connected to it in a suitable manner. Preferably the motor 5 is a synchronous permanent magnet motor. Preferably the brakes 7, 7′ are electromagnetic brakes which are arranged for example to press a braking shoe against a braking surface connected to the traction sheave 6 or separately from the traction sheave.
The motion of the motor can be controlled with a drive unit 15 as shown in
As shown in
The test load TL may be selected according to circumstances in a specific elevator installation. Preferably, the test load TL corresponds to a preselected overload, which is represented by a factor OL. Preferably the overload is selected OL=110% i.e. load 10% higher than a nominal load N of elevator car:
TL=OL*N, preferably TL=110%*N (1)
The method comprises confirming that an empty elevator car 2 is positioned at a test location stest, for example at the lowest or highest floor in the elevator hoistway 1.
The method further comprises gathering information of elevator balancing B and friction Fr of an elevator at the test location stest.
Balancing B may be a parameter registered into elevator control system. Balancing B may also be checked, for example from equation (5) in WO 2014135408 A1 called as a balancing weight mB. In said equation mB=[(PME,mid,up−PME,mid,dn) 2*g*vnom] mB represents the balancing weight difference in kilogram, vnom the nominal speed of the elevator, and g the gravitational acceleration 9.81 m/s2. According to this equation the balance at the middle location of the hoistway is obtained during a constant speed run by determining the motor current from which copper losses are removed in up and down directions and dividing the difference with the nominal velocity and g.
The balance check determines the balancing weight difference of the elevator. The balancing weight difference is the difference between the weight of the empty elevator car 2 and the weight of the counterweight 3 of the elevator. Further, the balancing B may be nominal balancing BN, or it may additionally contain position-dependent uncompensation term U, in addition to the nominal balancing BN:
B=B
N
+U (2)
Uncompensation is the position-dependent compensation error caused by moving components e.g. suspension ropes, hoisting ropes or compensation ropes of the elevator. It may be considered changing linearly as function of elevator car position s, such that nominal balancing BN is reached in the middle of elevator hoistway 1 for example. In general, the test method can be implemented at any floor or test location but in case the method is implemented at top and/or top floor in the hoistway, then a compensation is not required.
Friction Fr may be measured by moving the elevator car 2 very slowly up and down at the test location stest and measuring motor drive current in both directions. Force/current created by shaft friction (friction of the moving parts in the hoistway) is the calculated by (current upwards-current downwards)/2.
As the aforementioned force components have been determined, the test torque TM, in other words, assisting test torque, of the elevator hoisting motor 5 is determined based on said components TL, B and Fr:
T
M→(OL−B)*N+Fr (3)
In equation 3 above, balancing B is expressed as a percentage of nominal load N.
The hoisting machine brakes 7, 7′ are tested by opening one of the brakes at a time while keeping rest of the brakes engaged i.e. in their braking position. Torque is then applied, e.g. ramped up with an electrical motor 5 of the elevator hoisting machine 10 at most up to the required test torque TM, while observing motion state of the hoisting machine 10, for example observing movement of the traction sheave 6. If rotation of the hoisting machine 10 is observed, a signal indicating an operational anomaly of the brake or brake system is generated. This indication, preferably with more accurate situation analysis of for example at least one of the following: failed brake combination; statistical information, which torque value caused rotation etc. may be delivered e.g. to a service technician, to a remote monitoring center and/or to a cloud network for diagnosing the brake problem and scheduling maintenance.
Preferably, motor current IM corresponding to the required test torque TM is determined, as explained hereinafter. All hoisting machine brakes 7, 7′ are opened, hoisting motor 5 is activated, and motor current Ig required to keep elevator car 2 standstill with brakes open is registered. Required test current IM can then be determined from the current Ig, test load TL, balancing B and friction Fr, as follows:
I
M
→I
g*[(OL−B)*N/(B*N−Fr)−1] (4)
Use of this equation is possible when there is a linear relationship between motor current and motor torque. This is the case especially when hoisting motor is a synchronous permanent magnet motor.
Then current I at most up to the motor current IM is supplied to the windings of the hoisting motor 5 to generate the required assisting test torque TM; thereafter the test procedure continues in the same way as disclosed above for the other brakes of the hoisting machine 10.
According to a first example the method is implemented in following circumstances:
The brake test load to be verified on test is: 110%×1000 kg−50%×1000 kg=600 kg. In case of one failed brake set 7, 7′, remaining brake sets shall be capable of holding and decelerating 110% load. The drive unit 15 measures current Ig required to hold car 2 stationary when the brakes are not engaged. This current Ig represent the force to keep 500 kg stationary. Then one brake set is left open and others are closed. The drive unit 15 increases the current to motor by 0.1×Ig which corresponds to required test force.
Required test force representing the load of 600 kg< >IM=1.2×Ig
Needed force assistance from motor=600 kg−500 kg=100 kg< >0,2×Ig
IM→Ig*[(OL−B)*N/(B*N−Fr)−1]<->Ig*[(110−50)*1000/(0,5*1000)−1]=Ig*0,2
If it is detected that there is no movement on motor traction sheave 6 while test torque is been applied test is passed. Rest of the brake set combinations are tested by following the same procedure.
According to a second example the method is implemented in following circumstances:
The brake test load to be verified on test is: 110%×1000 kg−40%×1000 kg=700 kg. In case of one failed brake set 7, 7′, remaining brake sets shall be capable of holding and decelerating 110% load. The drive unit 15 measures current Ig required to hold car 2 stationary when the brakes are not engaged. This current Ig represent the force to keep 400 kg stationary minus 10 kg by friction Fr. Then one brake set is left open and others are closed. The drive unit 15 increases the current to motor by 0.41×Ig which corresponds to required test force.
Required test force representing the load of 700 kg< >IM=1.79×Ig
Needed force assistance from motor=700 kg−390 kg=310 kg< >0,79×Ig
IM→Ig*[(OL−B)*N/(B*N−Fr)−1]<->Ig*[(110−40)*1000/(0,4*1000−10)−1]=Ig*0,79
If it is detected that there is no movement of elevator car while test torque is been applied test is passed. Rest of the brake set combinations are tested by following the same procedure.
In the application, several details for the arrangement have been presented as preferred. This means that they are preferred, however they are not to be understood as necessary, because it may be that the arrangement can be implemented also without them.
It is to be understood that the above description and the accompanying figures are only intended to illustrate the present invention. It will be obvious to a person skilled in the art that the invention can be varied and modified without departing from the scope of the invention.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2021/068839 | Jul 2021 | US |
| Child | 17941499 | US |
