HK1189564B - Stop sequencing for braking device - Google Patents

Description

Stop sequencing for braking device

Technical Field

The present disclosure relates generally to braking devices and, in particular, to braking devices for use with elevators.

Background

In modern society, elevators have become ubiquitous machines for transporting people and cargo through multi-story buildings. Since the elevator is continuously operated throughout the day with frequent stops at the respective floors, the brake system of the elevator plays an important role in the smooth operation of the elevator.

Traction machines that use belt or rope driven systems to raise or lower an elevator car (such as those used in elevator systems) typically use mechanical or electromechanical braking systems to stop or temporarily maintain a particular action. For example, the electromechanical brakes of elevators typically utilize clutch-type braking mechanisms for supplying a holding or braking torque sufficient to slow or hold the elevator car in a fixed position. The braking torque supplied by the clutch-type brake may be mechanically generated by friction generated between a rotating brake disc rigidly attached to the machine shaft and a set of friction pads releasably placed in contact with a surface of the brake disc. Engagement or disengagement of the friction pads is electromechanically controlled by a brake coil. When the brake coil is activated, the magnetic attraction between the armature plate and the electromagnetic core causes the friction pads to disengage from the surface of the brake disc. When the brake coil is deactivated, a spring engaging the armature plate urges the armature plate into engagement with the surface of the brake disc. While such clutch-type brakes have proven effective and are still widely used today in various traction applications (e.g., elevators, etc.), they still have room for improvement.

For example, clutch-type brakes may not selectively apply different amounts of force to stop an elevator depending on the type of stop desired (e.g., emergency stop versus normal stop). A typical clutch-type brake is limited to its rated torque, which is also dictated by the mechanical limits of the brake, the material composition of its friction pads, etc. During an emergency situation, such as a loss of power to the building, the braking system must stop the elevator quickly. Such emergency stops are typically abrupt and cause the elevator car to stop with an emergency stop, which can be an uncomfortable experience for passengers riding in the elevator car. Since the elevator braking system provides the same braking torque for a normal stop as it provides for an emergency stop, the elevator car and passengers within the car may experience an emergency stop whenever the braking system is used to stop the elevator for an emergency stop. Thus, it follows that the clutch-type brake does not provide control or variation of the braking force to stop the elevator.

In view of the foregoing, improvements continue to be sought for providing an effective braking system for safely stopping an elevator while increasing the comfort of the stop to passengers.

Disclosure of Invention

According to one aspect of the disclosure, an elevator system is disclosed. An elevator system may include a car, a first brake having a first magnetic brake coil, and a brake control device having a brake power source. The first brake is movable between a disengaged position and an engaged position. The brake control device may be electrically connected to the first brake and may be configured to selectively delay movement of the first brake to the engaged position with a first residual current from the first brake coil. The first brake may be configured to be movable to a disengaged position when the first brake coil is energized by the brake power source, and may be configured to be movable to an engaged position when the first brake coil is de-energized. The first residual current may delay the movement of the first brake to the engaged position by slowing the rate of decay of the stored energy within the first brake coil. In an embodiment, the delay may be in the range of about 150 milliseconds to about 600 milliseconds. In some embodiments, movement of the first brake to the engaged position may be delayed in response to unintentional movement of the elevator car.

In some embodiments, the elevator system further includes a second brake having a second magnetic brake coil. The second brake may be electrically connected to the brake control device and may be movable between a disengaged position and an engaged position. The second actuator may have a second magnetic actuator coil. The second brake is movable from an engaged position to a disengaged position when the second brake coil is energized by the brake power source. The second brake may be configured to be movable to the engaged position when the second brake coil is de-energized. In an embodiment, the brake control device may be configured to selectively delay the movement of the second brake to the engaged position with a second residual current from the second brake coil.

According to another aspect of the disclosure, an elevator system may include a safety chain including a governor switch movable between an open position and a closed position. The safety chain may be electrically connected to the brake control device. In an embodiment, movement of the second brake to the engaged position may be delayed in response to the regulator switch transitioning to the open position. The elevator power source may be connected to the safety chain, wherein movement of the first brake may be delayed in response to a loss of power from the power source to the safety chain.

In accordance with another aspect of the present disclosure, a braking device for an elevator is disclosed. The brake system may include a first brake having a first magnetic brake coil and configured to be movable between a disengaged position and an engaged position, and a brake control device for selectively delaying movement of the first brake to the engaged position with residual current from the first brake coil, the brake control device being electrically connected to the first brake.

In an alternative embodiment, the braking system may include a second brake having a second magnetic brake coil and configured to be movable between a disengaged position and an engaged position, wherein the brake control device may selectively delay movement of the second brake to the engaged position with residual current from the second brake coil, the brake control device being electrically connected to the second brake.

In an embodiment, the brake control system can delay movement of the first brake in response to unintentional movement of the elevator car and/or a loss of power from the elevator power source. In embodiments including a second brake, the brake control device may delay movement of the second brake in response to an overspeed event. In an embodiment, such delays may be in the range of about 150 milliseconds to about 600 milliseconds.

In accordance with yet another aspect of the disclosure, a method of retrofitting an elevator system having a car, a first brake having a first magnetic brake coil, and a brake control device is disclosed. The method may include varying the brake control device to selectively delay activation of the first brake by controlling a rate of decay of stored energy within the first magnetic brake coil. The rate of decay may be controlled by recirculating the residual current through the first magnetic brake coil. In an embodiment, such delays may be in the range of about 150 milliseconds to about 600 milliseconds.

In an alternative embodiment, the method may further comprise varying the brake control means to selectively delay activation of the second brake by controlling the rate of decay of stored energy within the second magnetic brake coil. The rate of decay of the stored energy within the second magnetic brake coil can be controlled by recirculating the residual current through the second magnetic brake coil. In an embodiment, such delays may be in the range of about 150 milliseconds to about 600 milliseconds.

In an embodiment, the elevator system further comprises a safety chain having a governor switch movable between a closed position and an open position. The first brake may be activated before the second brake when the elevator car experiences unintended movement, and the second brake may be activated before the first brake when the governor transitions to the off position.

These and other aspects of the disclosure will be more readily apparent when the following detailed description is read in conjunction with the accompanying drawings.

Drawings

Fig. 1 is an exemplary elevator system that may use a brake control system constructed in accordance with the teachings of the present disclosure;

FIG. 2 is a schematic diagram illustrating one embodiment of a brake control system according to the teachings of the present disclosure;

FIG. 3 is an embodiment of a brake control device for use in the brake control system of FIG. 2; and

fig. 4 illustrates one embodiment of the interconnection of various electrical components of the brake control device of fig. 3 with an elevator system.

While the disclosure is susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the disclosure to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the disclosure.

Detailed Description

Referring now to fig. 1, an exemplary elevator system 20 is schematically illustrated. It will be understood that the form of the elevator system 20 shown in fig. 1 is for exemplary purposes only and is used to present a background for the various components of a typical elevator system.

As shown in fig. 1, an elevator system 20 may be at least partially present in a hoistway 22 vertically disposed within a multi-story building 24. Some components of the elevator system may be present outside of the hoistway 22, for example, in a machine room above the hoistway. Generally, the hoistway 22 may be a hollow shaft disposed within a central portion of the building 24, wherein multiple hoistways are provided if the building is of sufficient size and includes multiple elevators. The rails 26 and 28 may extend substantially the length of the hoistway 22. An elevator car 30 is slidably mounted on the pair of rails 26 (only one rail 26 is shown in fig. 1 for clarity) and a counterweight 32 is slidably mounted on the pair of rails 28 (only one rail 28 is shown in fig. 1 for clarity). Although not depicted in detail in fig. 1, those of ordinary skill in the art will appreciate that both the car 30 and counterweight 32 may include roller assemblies 34, bearings, etc. for smooth movement along the rails 26 and 28. Roller fittings, bearings, etc. may also be slidably mounted to the rails 26 and 28 in a secure manner.

To move the car 30, and thus the passengers and/or cargo loaded thereon, a machine (31) including an electric motor 36 may typically be provided at the top of the hoistway 22 or in a machine room above the hoistway 22. An electronic controller 38 may be electrically coupled to the motor 36, which electronic controller 38 in turn may be electrically coupled to a plurality of operator interfaces 40 provided on each floor to invoke the elevator cars 30, and an operator interface 42 provided on each car 30 to allow its passengers to specify the orientation of the cars 30.

The safety chain circuit 54 and the power supply 56 may also be electrically coupled to the electronic controller 38. A drive shaft 44 may mechanically extend from the motor 36, which drive shaft 44 in turn may be operably coupled to the traction sheave 46, and may also extend to be operatively coupled to a brake apparatus 52. In some cases, the traction sheave 46 may be part of the drive shaft 44.

A tension member 48 may be continuous around the pulley 46, the tension member 48 such as a round rope or a flat belt. The tension member 48, in turn, may be operatively coupled to the counterweight 32 and the car 30 in any suitable arrangement of ropes. Of course, many different embodiments or arrangements of these members are possible with typical systems including multiple tension members 48 and various arrangements for the motor and sheaves of the elevator system 20.

The elevator system 20 may also include a brake control system 58. In some embodiments, the machine 31 for raising and lowering the elevator car 30 may include a brake control system 58. As shown in fig. 2, the brake control system 58 may be electrically connected to the power supply 56 and mechanically coupled to the motor 36 of the elevator system 20. Brake control system 58 may include a brake apparatus 52 electrically connected to a brake control device 60.

The braking device 52 may include at least one brake. In an exemplary embodiment, the brake apparatus 52 may include a first brake (e.g., service brake 66) and a second brake (e.g., emergency brake 62). The first brake may be a separate unit from the second brake, or the first brake and the second brake may be components of a single brake unit. The emergency brake 62 may have a magnetic emergency brake coil 64 and the service brake 66 may have a magnetic service brake coil 68. When energized, the brake coils 64, 68 cause the brakes 62, 66 to disengage, thereby applying no braking force to slow or stop the elevator car 30. When the brake coils 64, 68 are not energized (or are not fully energized), the brakes 62, 66 are engaged and a braking force is applied to the elevator car (which may also be referred to as "dropping the brakes").

The brake control device 60 may be coupled to the brake coils 64, 68 of the brake apparatus 52, and may selectively control the attenuation of stored energy within one or both of the coils 64, 68 during certain operating conditions. In an embodiment, brake control device 60 may be part of electronic controller 38. In other embodiments, brake control device 60 may be separate from electronic controller 38 or incorporated into other components in elevator system 20. In an embodiment, brake control device 60 may control the decay of stored energy within each brake coil 64, 68 such that one of brakes 62, 66 may be engaged relatively quickly, and the engagement of the other brake may be delayed by the natural decay of stored energy within its associated brake coil. Sequencing of the application of the emergency brake 62 and the service brake 66 may reduce the initial hysteresis force applied to the drive shaft 44 (fig. 1) that results in a lower deceleration rate of the elevator car 30. Operating conditions of the elevator system during which attenuation of stored energy within one or both coils that may be used is selectively controlled include, for example, power loss, unintended car movement, ascending car overspeed, and the like.

The brake control device 60 may include a brake pick-up (brakeplick) 70 having a plurality of contacts, a power monitoring relay 72 having a plurality of contacts, an overspeed relay 74 having a plurality of contacts, an Unintentional Car Movement (UCM) relay 76, and a safety chain relay 78. The brake pick-up 70 is used to close the switches 80 and 82 to energize the brake coils 64 and 68 at the beginning of elevator operation and to open the switches 80 and 82 at the end of elevator operation. In an embodiment, power monitoring relay 72 may monitor Alternating Current (AC) power. In other embodiments, the power monitoring relay 72 may monitor Direct Current (DC) power, or DC and AC power. As discussed further below, the brake control device 60 may also include a brake power supply, a plurality of diodes, and a plurality of snubbers. A snubber may be used with the brake control device 60 discussed herein to prevent damage to brake control device elements when current is suddenly interrupted.

Turning now to FIG. 3, an exemplary brake control device 60 is disclosed. Brake control device 60 may be electrically connected to emergency brake 62 by emergency brake coil 64 and to service brake 66 by service brake coil 68. A first brake switch 80 may be connected to the UCM relay 76. As shown in fig. 3, brake control device 60 may include a first diode 84, which first diode 84 may be connected in parallel with emergency brake coil 64 through a first contact 86 of overspeed relay 74 and a main contact 88 of first power monitoring relay 72. Overspeed relay 74 is used to open switch 86 during an overspeed event to disconnect diode 84 to prevent current circulation in emergency brake coil 64. The first damper 90 may also be connected in parallel with the emergency brake coil 64. The UCM relay 76 may be connected to the emergency brake coil 64. The portions of the brake control device 60 and the emergency brake coil 64 described above may be collectively referred to as an "emergency brake circuit" 92. In an embodiment, the emergency brake circuit 92 may receive power from a brake power source 94, which brake power source 94 may be part of the brake control device 60.

As further shown in fig. 3, a second brake switch 82 may be connected to safety chain relay 78. Safety chain relay 78 may be connected to service brake coil 68. A second diode 96 may be connected in parallel with service brake coil 68 through a second contact 98 of overspeed relay 74 and a secondary contact 100 of power monitoring relay 72. The buffer 91 may also be connected in parallel with the service brake coil 68. A third diode 102 may be connected to safety chain relay 78. The portions of the brake control device 60 and the service brake coil 68 described above may be collectively referred to as a "service brake circuit" 104. Service brake circuit 104 may receive power from brake power supply 94.

As schematically shown in fig. 4, the power supply 56 may energize the safety chain 54 and the power relay 72. It should be understood that the power supply 56 may energize other components within the elevator system 20, such as, but not limited to, the electronic controller 38 and the operator interfaces 40, 42. Further, the power supply 56 may provide AC power and/or DC power depending on the power needs of the energized components. Further, the elevator system 20 may incorporate more than one power supply to energize various components within the system 20. For example, in an embodiment, separate brake power sources 94 may be used to provide power to the emergency brake circuit 92 and the service brake circuit 104.

The safety chain 54 may include a regulator 106 and various Electrical Protection Devices (EPDs)108 electrically connected together. Governor 106 monitors the speed of car 30. In alternative embodiments, devices other than the governor 106 may also monitor the speed of the car 30, including overspeed. The EPDs108 can monitor the safety status of various components of the elevator system 20. The regulator 106 and the EPDs108 may be connected together in a series circuit. The safety chain 54 may be "open" if one of the regulators 106 or the EPDs108 is not closed (closed circuit). Typically, the elevator car 30 is stopped or held in a stop when the safety chain 54 is broken. Such a disconnect condition may be triggered by governor 106 when the speed of car 30 exceeds a threshold. An open state may also be triggered when an unsafe condition is detected by EPD 108. As shown in fig. 4, overspeed relay 74, UCM relay 76, and safety chain relay 78 may be electrically connected to safety chain 54. In some embodiments, these elements may be part of the safety chain 54. Further, the brake picking member 70 may be energized by the power supply 56.

As shown in fig. 3-4, during normal operation of the elevator system 20, the first and second brake switches 80 and 82 may be closed, the safety chain relay 78 may be closed, the UCM relay 76 may be closed, and both the overspeed relay 74 and the power monitoring relay 72 may be energized. When energized, in the emergency brake circuit 92, the first overspeed relay contact 86 may be closed and the main power monitor relay contact 88 may be open. In the service brake circuit 104, the second overspeed relay contact 98 can be open and the secondary power monitoring relay contact 100 can be closed. In this embodiment, the second diode 96 is substantially disconnected from the service brake coil 68 because the second overspeed relay contact 98 is open.

The motor functions to stop the elevator when a signal is received to stop the elevator car 30 at a floor for passengers to get on and off. Service brake 66 and emergency brake 62 may be used to hold elevator car 30 in place during a stop. Accordingly, the first and second brake switches 80 and 82 may be turned off. However, in the embodiment shown in fig. 3, some of the residual current flowing from the service brake coil 68 may continue to circulate through the third diode 102 and the safety chain relay 78 back through the service brake coil 68. Some of the residual current from the emergency brake coil 64 may continue to circulate through the first diode 84 and the first overspeed relay contact 86 back to the emergency brake coil 64. Because such circuitry provides a low impedance current path for the residual current from the brake coils 64, 68, the current flowing through the brake coils 64, 68 decays relatively slowly. This slow decay in both brake coils 64, 68 delays the application of both service brake 66 and emergency brake 62 when power is removed by brake switches 80, 82. When the current dissipation exceeds a threshold value, it can no longer energize the coil and the corresponding brake will be engaged (dropped). In an embodiment, the delay may be in the range of about 150 milliseconds to about 600 milliseconds.

As is known in the art, when the speed of the moving elevator car 30 exceeds a defined threshold, overspeed of the car in either direction occurs. In the event of such an overspeed, the governor 106 is opened. In the embodiment shown in fig. 3-4, the opening of regulator 106 interrupts (disconnects) safety chain 54 and causes each of UCM relay 76, overspeed relay 74, and safety chain relay 78 to open. Although the regulator 106 is open, the power monitoring relay 72 may remain energized.

During an overspeed event, both the first overspeed relay contact 86 and the main power monitor relay contact 88 can be opened in the emergency brake circuit 92. This may cause first diode 84 to be disconnected from emergency brake coil 64. Thus, the current in the emergency brake coil 64 dissipates relatively quickly and the emergency brake 62 is engaged once the current becomes too weak to continue energizing the emergency brake coil 64.

In the embodiment shown in fig. 3, opening safety chain relay 78 disconnects third diode 102 from service brake coil 68. In the service brake circuit 104, both the second overspeed relay contact 98 and the secondary power monitoring relay contact 100 are closed, and thus the second diode 96 is connected in parallel with the service brake coil 68. Because this arrangement provides a low impedance circulation path for the residual current, some of the residual current from the service brake coil 68 may continue to circulate through the second diode 96, the second overspeed relay contact 98 and the secondary power monitor relay contact 100 back to the service brake coil 68. This slows the current decay in service brake coil 68, thus delaying the application of service brake 66. In an embodiment, the delay may be in the range of about 150 milliseconds to about 600 milliseconds. Once the residual current becomes too weak to continue energizing the service brake coil 68, the service brake 66 is engaged and the spring in the brake overcomes the force created by the energized coil and applies a braking force. In contrast, the residual current of the emergency brake coil 64 does not have a low impedance circulation path and decays rapidly, thus causing the emergency brake 62 to fall generally faster than the service brake.

As is known in the art, at times, the elevator car 30 may experience Unintentional Car Movement (UCM) during operation. An example of such a UCM event is movement of the car (30) while the car (30) is at a landing and the door is open or unlocked. In the event that UCM is sensed during operation, both UCM relay 76 and safety chain 54 are open. In the embodiment shown in fig. 3-4, opening safety chain 54 also opens safety chain relay 78, thus disconnecting third diode 102 from service brake coil 68. As shown in fig. 3-4, both the overspeed relay 74 and the power monitoring relay 72 are energized. When energized, in the emergency brake circuit 92, the first overspeed relay contact 86 may be closed and the main power monitor relay contact 88 may be opened. In the service brake circuit 104, the second overspeed relay contact 98 can be opened and the secondary power monitoring relay contact 100 can be closed. Since the second overspeed relay contact 98 is open, the second diode 96 is disconnected from the service brake coil 68. A first diode 84 is coupled in parallel with the emergency brake coil 64 through a first overspeed relay contact 86. Thus, during a UCM event, the service brake 66 drops without delay because the remaining service brake coil 68 current does not have a low impedance circulation path. Instead, application (or dropping) of the emergency brake 62 is delayed by the residual current being recirculated through the emergency brake coil 64. The emergency brake 62 will be engaged once the residual current becomes too weak to energize the emergency brake coil 64. In an embodiment, the delay may be in the range of about 150 milliseconds to about 600 milliseconds.

As shown in fig. 3-4, in the event of an elevator loss of power, both the overspeed relay 74 and the power monitoring relay 72, as well as the UCM relay 76 and the safety chain relay 78, may be de-energized. In this case, in the emergency brake circuit 92, the first overspeed relay contact 86 can be opened and the main power monitoring relay contact 88 can be closed. In the service brake circuit 104, the second overspeed relay contact 98 can be closed and the secondary power monitoring relay contact 100 can be opened.

In the embodiment of fig. 3, a first diode 84 is coupled in parallel with the emergency brake coil 64 through a main power monitor relay contact 88. On the other hand, since the sub-power monitoring relay contact 100 is open, the second diode 96 is substantially cut off from the service brake coil 68. In addition, the third diode 102 is disconnected from the service brake coil 68 by the safety chain relay 78. Since the service brake 66 current does not have a low impedance circulation path, the current in the service brake coil 68 will dissipate relatively quickly, allowing the service brake 66 to be engaged relatively quickly. Application of the emergency brake 62 will be delayed by some recirculation of the remaining emergency brake coil current back to the emergency brake coil 64 through the main power monitoring relay contact 88. The emergency brake 62 will be engaged once the residual current becomes too weak to energize the emergency brake coil 64. In an embodiment, the delay may be in the range of about 150 milliseconds to about 600 milliseconds.

Industrial applications

From the foregoing, it can be seen that the present disclosure sets forth an elevator with a novel braking system that reduces discomfort to passengers when the elevator car is stopped by the brake during an emergency stop or power loss event. Elevators are continuously used to transport passengers from floor to floor, creating frequent stops. The braking system of the present disclosure reduces discomfort to the occupant even in the event of an emergency. An emergency situation may occur when an elevator experiences a loss of power or a fault (e.g., an overspeed or UCM event). In an emergency, the braking device ensures a smooth stop of the elevator.

An elevator system may include a car, a safety chain including a governor switch movable between an open position and a closed position, a first brake having a first magnetic brake coil, a second brake having a second magnetic brake coil, and a brake control device having a brake power supply. The first brake is movable between a disengaged position and an engaged position. The second brake is movable between a disengaged position and an engaged position. The brake control device may be electrically connected to the first and second brakes and the regulator switch, and may be configured to selectively delay movement of the first and second brakes to the engaged position with a residual current from the respective brake coils. Selectively sequencing the engagement of the delay brake may at least soften the stopping of the elevator car for passengers.

While only certain embodiments have been set forth, alternatives and modifications will be apparent from the foregoing description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure.

Claims (24)

1. An elevator system (20), comprising:

a car (30);

a first brake (62) having a first magnetic brake coil (64), the first brake (62) being movable between a disengaged position and an engaged position; and

a brake control device (60) having a brake power source (94), the brake control device (60) being electrically connected to the first brake (62) and configured to selectively delay movement of the first brake (62) to the engaged position with a first residual current from the first magnetic brake coil (64).

2. The elevator system (20) of claim 1, wherein the first brake (62) is configured to be movable to the disengaged position when the first magnetic brake coil (64) is energized by the brake power source (94) and is configured to be movable to the engaged position when the first magnetic brake coil (64) is de-energized.

3. The elevator system (20) of claim 1, further comprising a second brake (66) having a second magnetic brake coil (68), the second brake (66) electrically connected to the brake control device (60), the second brake (66) movable from an engaged position to a disengaged position when the second magnetic brake coil (68) is energized by the brake power source (94) and movable to the engaged position when the second magnetic brake coil (68) is de-energized.

4. The elevator system (20) of claim 3, wherein the brake control device (60) is further configured to selectively delay movement of the second brake (66) to the engaged position with a second residual current from the second magnetic brake coil (68).

5. The elevator system of claim 4, further comprising a safety chain (54) electrically connected to the brake control device (60), the safety chain (54) including a governor switch (106) movable between an open position and a closed position.

6. The elevator system of claim 5, wherein movement of the second brake (66) to the engaged position is delayed in response to the governor switch (106) transitioning to the disengaged position.

7. The elevator system of claim 1, further comprising a safety chain (54) electrically connected to the brake control device (60), the safety chain (54) including a regulator switch (106) movable between an open position and a closed position and an elevator power source (56) connected to the safety chain (54), wherein movement of the first brake (62) is delayed in response to a loss of power from the elevator power source (56) to the safety chain (54).

8. The elevator system (20) of claim 1, wherein the first residual current delays movement of the first brake (62) to the engaged position by slowing a rate of decay of stored energy within the first magnetic brake coil (64).

9. The elevator system (20) of claim 8, wherein the delay is in the range of 150 milliseconds to 600 milliseconds.

10. The elevator system (20) of claim 8, wherein movement of the first brake (62) to the engaged position is delayed in response to unintentional car movement of the car (30).

11. The elevator system of claim 1, wherein the first brake (62) is part of a machine (31) for raising and lowering the car (30).

12. A braking system (58) comprising:

a first brake (62) having a first magnetic brake coil (64), the first brake (62) being movable between a disengaged position and an engaged position; and

a brake control device (60) for selectively delaying movement of the first brake (62) to the engaged position with a residual current from the first magnetic brake coil (64), the brake control device (60) being electrically connected to the first brake (62).

13. The braking system (58) of claim 12, wherein the brake control device (60) delays movement of the first brake (62) in response to an unintentional car movement event.

14. The braking system (58) of claim 12, further comprising a second brake (66) electrically connected to the brake control device (60), the second brake (66) having a second magnetic brake coil (68) and being configured to be movable between a disengaged position and an engaged position, wherein the brake control device (60) selectively delays movement of the second brake (66) to the engaged position with a residual current from the second magnetic brake coil (68).

15. The braking system (58) of claim 14, wherein the brake control device (60) delays movement of the second brake (66) in response to an overspeed event.

16. The braking system (58) of claim 12, wherein the braking system (58) is electrically connected to an elevator power source (56), and the brake control device (60) delays movement of the first brake (62) in response to a loss of power from the elevator power source (56).

17. The braking system (58) of claim 12, wherein the delay is in a range of 150 milliseconds to 600 milliseconds.

18. A method of retrofitting an elevator system (20), the elevator system (20) having a car (30), a first brake (62), and a brake control device (60), the first brake (62) having a first magnetic brake coil (64), the method comprising:

varying the brake control device (60) to selectively delay activation of the first brake (62) by controlling a rate of decay of stored energy within the first magnetic brake coil (64).

19. The method of claim 18, wherein the rate of decay of stored energy within the first magnetic brake coil (64) is controlled by recirculating residual current through the first magnetic brake coil (64).

20. The method of claim 18, wherein the delay is in a range of 150 milliseconds to 600 milliseconds.

21. The method of claim 18, further comprising varying the brake control device (60) to selectively delay activation of a second brake (66) by controlling a decay rate of stored energy within a second magnetic brake coil (68), wherein the elevator system (20) further includes the second brake (66) having the second magnetic brake coil (68).

22. The method of claim 21, wherein the rate of decay of stored energy within the second magnetic brake coil (68) is controlled by recirculating residual current through the second magnetic brake coil (68).

23. The method of claim 22, wherein the elevator system (20) further comprises a safety chain (54) having a governor switch (106) movable between a closed position and an open position.

24. The method of claim 23, wherein the first brake (62) is activated before the second brake (66) when the car (30) experiences an unintended car movement event, and the second brake (66) is activated before the first brake (62) when the governor switch (106) transitions to the off position.