HK1108678B - Elevator testing system - Google Patents

Description

Elevator test system

Technical Field

The present invention relates to elevator systems. In particular, the invention relates to a method and a system for testing the operation of a safety circuit in an elevator system, especially already existing, in order to achieve a desired safety level.

Background

It is of primary importance for the operation of an elevator system that the elevator system should function without faults and especially in a predictable manner. Especially in the case of systems, such as remote monitoring systems, connected to the safety circuit of an already existing elevator, it must be ensured that the operation of the safety circuit of the elevator system complies with the desired safety standards even after the connection of said systems.

Elevator systems employ various monitoring devices and methods to ensure the safety of the elevator. One of them is the so-called electric safety circuit. The safety circuit consists of safety device contactors connected in series. If either safety device breaks the safety circuit, the elevator will stop or will not start moving. The safety circuit monitors e.g. car doors, hoistway doors, locks etc. The safety circuit is open if e.g. the elevator car door is open.

Fig. 1a shows an example of a safety circuit configuration. In fig. 1a, there are three safety contacts 10, 12, 14 connected in series. The safety circuit is connected to the main contactor 16 and the monitoring card 106, which is shown as a highly simplified resistor circuit. The main contactor 16 and the monitoring card 106 are connected to a common ground point 18 (neutral ground). The worst fault situation that can be caused by the monitoring card is illustrated in fig. 1b, where the neutral conductor connected to the neutral ground point 18 is disconnected (110). In this case, the fault may cause current to flow through the main contactor sufficient to keep the main contactor energized "while the safety circuit is open.

We assume that each resistor 100, 102, 104 has a size of 300 k. In this case, the minimum bridge resistance has a magnitude of 450 k. In other words, two parallel 300 k-resistors are connected in series with a third 300 k-resistor. Fig. 1c shows a circuit corresponding to the circuit in fig. 1 b. Resistor 112 has a magnitude of 450 k. If the safety circuit voltage (U)_max) Is 230Vac, the maximum possible fault current will be about 0.5A.

Based on the above various factors, it is possible that the fault current generated in the event of a fault will be sufficient to keep the main contactor energized. If the main contactor remains energized even when the safety circuit is open, the elevator does not comply with the safety regulations.

Elevator safety regulations recommend that the neutral ground of the safety circuit should be connected to the neutral ground via an analysis card, such as e.g. a remote monitoring card. The recommendations given by the safety regulations determine the safest way to implement the connection of the analysis card to the safety circuit. If a deviation from this is chosen, the corresponding safety level must be verified by a risk analysis. A common recommendation to avoid a circuit bypass current condition is to direct the return current of the main contactor to neutral ground via the neutral conductor of the analysis card, so that the safety circuit cannot be erroneously bypassed in the event of a fault. Such a circuit is shown in fig. 1 d. However, in many existing elevator control systems, it is often difficult to later change the connections.

Disclosure of Invention

The object of the invention is to disclose a method and a system for ensuring the safety of the safety circuit of an elevator system when a monitoring card is connected to the safety circuit of the elevator system.

According to the invention, a method is provided for ensuring the operation of a safety circuit of an elevator or escalator, said safety circuit comprising safety contacts in series with a contactor, characterized in that the method comprises the steps of:

determining a maximum bypass current to the contactor in a fault condition;

connecting a test device in series with the safety circuit, the test device including at least one resistor to generate an expected test current greater than the maximum bypass current; and

the neutral point of the safety circuit is shifted if the contactor remains energized by the aforementioned test current.

Preferably, the expected test current is generated when the elevator or escalator is operating.

Preferably, the method is used to test each of the parallel safety circuits separately.

Preferably, the test device is connected in series with the safety circuit at a position in the safety circuit closest to the contactor.

According to the invention, there is provided a system for ensuring the operation of a safety circuit of an elevator or escalator, said safety circuit comprising safety contacts connected in series to a contactor, characterized in that it further comprises:

a test device connected in series with the safety circuit and comprising at least one resistor for generating a desired test current for the contactor, said test current being greater than the maximum current flowing to the contactor in case of a fault; and

means for shifting the neutral point (18) of the safety circuit in the case where the contactor remains energized by the aforementioned test current.

Preferably the test device is arranged to generate said expected test current when the elevator or escalator is in motion.

Preferably, the test device is used to test each of the parallel safety circuits separately.

Preferably, the test device is connected in series with the safety circuit at a position in the safety circuit closest to the contactor.

Inventive embodiments are also presented in the description part and drawings of the present application. The inventive content disclosed in the application can also be defined in different ways. The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of explicit or implicit sub-tasks or in respect of advantages or sets of advantages achieved. In this case, some of the features included in some aspects may be superfluous from the point of view of separate inventive concepts. Within the framework of the basic idea of the invention, features of different embodiments of the invention can be applied in conjunction with other embodiments.

The invention relates to a method for ensuring the operation of a safety circuit of an elevator or escalator, said safety circuit comprising safety contacts connected in series with a contactor. In the method, a maximum bypass circuit to the contactor is determined under a certain fault condition; a test device connected in series with the safety circuit, the test device including at least one resistor to generate an expected test current greater than the maximum bypass current; and shifting the neutral point of the safety circuit if the contactor remains energized by the aforementioned test current.

In an embodiment of the invention, the test current is generated when the elevator or escalator is running.

In an embodiment of the invention, each parallel circuit is tested separately in case of parallel safety circuits.

In an embodiment of the invention, the testing device is connected to a point in the safety circuit located closest to the contactor.

The invention also relates to a system for ensuring the operation of a safety circuit of an elevator or escalator, said safety circuit comprising safety contacts connected in series with a contactor. The system further comprises a test device connected in series to the safety circuit and comprising at least one resistor for generating a desired test current for the contactor, said test current being greater than the maximum current flowing to the contactor in the event of a fault, and means for shifting the neutral point of the safety circuit in the event of a fault in which the contactor remains supplied by the aforesaid test current.

In an embodiment of the invention the test device is used to generate a test current when the elevator or escalator is running.

In an embodiment of the invention, the testing device is adapted to test each parallel circuit separately in case of parallel safety circuits.

In an embodiment of the invention, the test device is connected to a point in the safety circuit located closest to the contactor.

The present invention has several advantages over existing solutions. The present invention makes it possible to determine whether it is necessary to shift the neutral point. By applying the invention it is easy to test the elevator safety circuit in different operating states of the elevator, such as when the elevator car is moving.

By following the procedure disclosed in the invention, a sufficient level of elevator safety can be ensured without the need to pass the neutral conductor of the main contactor through the analyzing card to the neutral point.

Drawings

In the following, the invention will be described in detail with reference to embodiments, in which

FIGS. 1a, 1b, 1c and 1d are block diagrams of prior art safety circuits;

FIG. 2 is a block diagram of the test apparatus of the present invention for securing a safety circuit; and

fig. 3 is a block diagram of a safety circuit in which the connection points of the test device are indicated.

Detailed Description

The present invention will be described in detail with reference to fig. 2 and 3. Fig. 2 is a block diagram of the test apparatus of the present invention for securing the safety circuit, and fig. 3 is a block diagram of the branch safety circuit, showing points to which the test apparatus is connected.

The test device 202 shown in fig. 2 includes a switch 200, a lamp 24 and a resistor 26. The switch 200 is used to open the safety circuit, the resistor 26 is used to determine the value of the test current, and a lamp, such as an LED lamp (LED is a light emitting diode), is used to detect the test current. The test device 202 is connected in series with the safety circuit at the point closest to each main contactor, in other words, at points 301a and 301b as shown in fig. 3. If the safety circuit comprises several branches, each branch is tested separately.

In the actual test of the safety circuit, the elevator or escalator is operated while the switch 200 of the test device 202 is closed. When the switch 200 is open, the main contactors 16 should open and the elevator should stop immediately. The lamp 24, such as an LED lamp (LED is a light emitting diode), confirms that the test current flows through the test device 202 and that the test current is actually connected to the safety circuit. Once the safety circuit testing is completed, the testing device 22 is removed and the original safety circuit connections are restored.

If, after the switch 200 has been opened, the main contactors 16 remain energized and the elevator does not stop, the test device 202 reveals a situation in which the safety circuit connection fails the test. As a consequence of the detection of such a situation, the neutral point 18 has to be shifted so that it crosses the analysis card 106 (see fig. 1 d).

In the case where the safety circuit voltage is 230VAC, the maximum overflow current (spill current) is about 0.5mA in the case shown in fig. 1 b. For the safety circuit to work adequately acceptable, the test current of the main contactor 16 must be greater than the maximum overflow current, for example three times the maximum overflow current with a safety factor of 3, i.e. about 1.5mA in the case shown in fig. 1 b. To determine an acceptable test current and/or safety factor, various risk analysis methods may be utilized. This ensures that the main contactor 16 will not remain connected. If the factor is 3, the test resistance 26 of the test device 202 has a maximum value of 150K Ω in the case shown as an example.

The operation of the safety circuit must be ensured for either direction of movement of the elevator, since the safety circuit can control different devices depending on the direction of movement of the elevator.

The above-described method of testing a safety circuit is designed for use especially in old elevators. In newer elevators, the elevator safety circuit is generally designed in such a way that the neutral ground is passed over the analysis card, taking into account the situation of the aforementioned safety circuit.

One of the objects of the invention is to avoid unnecessary shifting of the neutral point. According to the disclosed test method, it can be determined whether the neutral point needs to be shifted. At the same time, unnecessary shifting of the neutral point is avoided.

Another object of the invention is to respond to high demands regarding existing elevator safety systems. In response to higher demand levels, the test arrangement of the present invention is employed, wherein the presence of an excessive holding current (holding current) in the safety circuit is determined to be impossible.

It is obvious to the person skilled in the art that the invention is not limited to the embodiments described above, in which the invention is described, but that many variations and different embodiments of the invention are possible within the scope of the inventive concept.

Claims (8)

1. A method for ensuring the operation of the safety circuit of an elevator or escalator, said safety circuit comprising safety contacts (10, 12, 14) in series with a contactor (16), characterized in that the method comprises the steps of:

determining a maximum bypass current to the contactor in a fault condition;

connecting a test device in series with the safety circuit, the test device including at least one resistor to generate an expected test current greater than the maximum bypass current; and

if the contactor remains energized by the aforementioned test current, the neutral point (18) of the safety circuit is shifted.

2. Method according to claim 1, characterized in that the expected test current is generated when the elevator or escalator is running.

3. A method according to claim 1, characterized in that the method is used for testing each of the parallel safety circuits individually.

4. A method according to claim 1, characterized in that the testing device is connected in series to the safety circuit at a position (301a, 301b) in the safety circuit closest to the contactor (16).

5. A system for ensuring the operation of a safety circuit of an elevator or escalator, which safety circuit comprises safety contacts (10, 12, 14) connected in series to a contactor (16), characterized in that the system further comprises:

a test device (202) connected in series with the safety circuit and comprising at least one resistor (26) for generating an expected test current for the contactor (16), said test current being greater than a maximum current flowing to the contactor in case of a fault; and

means for shifting the neutral point (18) of the safety circuit in the case where the contactor remains energized by the aforementioned test current.

6. A system according to claim 5, characterized in that the test device (202) is arranged to generate said desired test current when the elevator or escalator is in motion.

7. A system according to claim 5, characterized in that the testing means (202) are arranged to test each of the parallel safety circuits individually.

8. A system according to claim 5, characterized in that the test device is connected in series with the safety circuit at a position (301a, 301b) in the safety circuit closest to the contactor (16).