Elevator braking in a battery powered elevator system

• US 9,586,789 B2
• Filed: 08/13/2013
• Issued: 03/07/2017
• Est. Priority Date: 08/13/2013
• Status: Active Grant

• Current Assignee: Otis Elevator Company (Otis Worldwide Corp.)
• Original Assignee: Otis Elevator Company (Otis Worldwide Corp.)
• Inventors: Agirman, Ismail, Marvin, Daryl J.
• Primary Examiner(s): Horn, Robert W
• Application Number:
  US14/911,378
• Publication Number:
  US 20160194179A1
• Time in Patent Office: 1,302 Days
• US Class Current: 1/1
• CPC Class Codes: B66B 1/32 effective on braking devices , e.g. acting on electrically controlled brakes brake control H02P, lift brakes per se B66B5/02
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence
• CPC Class Codes: H02P 3/18 for stopping or slowing an ac motor

Abstract

An elevator system includes a battery; a machine having a motor to impart motion to an elevator car; an inverter having a plurality of switches to convert DC power from the battery to AC power for the machine in a motoring mode; a speed sensor coupled to the machine, the speed sensor to generate a speed signal indicative of machine speed; and a controller to apply braking signals to a group of the switches in a braking mode, the braking signals having a duty cycle in response to the speed signal.

Claims

1. An elevator system comprising:

a battery;

a machine having a motor to impart motion to an elevator car;

an inverter having a plurality of switches to convert DC power from the battery to AC power for the machine in a motoring mode;

a speed sensor coupled to the machine, the speed sensor to generate a speed signal indicative of machine speed; and

a controller to apply braking signals to a group of the switches in a braking mode, the braking signals having a duty cycle in response to the speed signal.

2. The elevator system of claim 1 wherein:

the braking signals have a common duty cycle.

3. The elevator system of claim 1 wherein:

the braking signals have different duty cycles.

4. The elevator system of claim 1 wherein:

the group of switches is a subset of the plurality of switches.

5. The elevator system of claim 1 wherein:

the plurality of switches includes the group of switches and a further group of switches, the further group of switches being non-conductive during the braking mode.

6. The elevator system of claim 5 further comprising:

a first DC link connecting the battery to the further group of switches; and

a second DC link connecting the battery to the group of switches.

7. The elevator system of claim 6 wherein:

the first DC link has a positive DC voltage.

8. The elevator system of claim 1 wherein:

the braking mode is entered upon opening of an elevator safety chain.

9. The elevator system of claim 1 wherein:

the duty cycle of at least one of the braking signals increases with time in braking mode.

10. A method of controlling an elevator system having a machine that imparts motion to an elevator car and a battery, the method comprising:

determining if a braking mode has been entered;

in braking mode, opening a first group of switches that couple the machine to the battery;

detecting a speed signal indicative of speed of the machine; and

applying braking signals to a second group of switches that couple the machine to the battery, the braking signals having a duty cycle in response to the speed signal.

11. The method of claim 10 wherein:

the braking signals have a common duty cycle.

12. The method of claim 10 wherein:

the braking signals have different duty cycles.

13. The method of claim 10 wherein:

the braking mode is entered upon opening of an elevator safety chain.

14. The method of claim 10 wherein:

the duty cycle of at least one of the braking signals increases with time in braking mode.

15. A motor control system comprising:

a battery;

a machine having a motor;

an inverter having a plurality of switches to convert DC power from the battery to AC power for the machine in a motoring mode;

a speed sensor coupled to the machine, the speed sensor to generate a speed signal indicative of machine speed; and

a controller to apply braking signals to a group of the switches in a braking mode, the braking signals having a duty cycle in response to the speed signal.