WO2008085169A1

WO2008085169A1 - Thermoelectric thermal management for drive circuitry and hoist motors in an elevator system

Info

Publication number: WO2008085169A1
Application number: PCT/US2007/000739
Authority: WO
Inventors: Lei Chen; Mikhail B. Gorbounov
Original assignee: Otis Elevator Company
Priority date: 2007-01-11
Filing date: 2007-01-11
Publication date: 2008-07-17

Abstract

A thermoelectric thermal management system (38) provides thermoelectric cooling or heating to maintain hoist motors (18a-18c) and motor drive circuitry (24, 30a-30c) of an elevator system (10) within a desired operating temperature range.

Description

THERMOELECTRIC THERMAL MANAGEMENT FOR DRIVE CIRCUITRY AND HOIST MOTORS IN AN ELEVATOR SYSTEM

REFERENCE TO COPENDING APPLICATIONS Reference is made to copending applications entitled THERMOELECTRIC THERMAL MANAGEMENT SYSTEM FOR THE ENERGY STORAGE SYSTEM IN A REGENERATIVE ELEVATOR, and THERMOELECTRIC TEMPERATURE CONTROL WITH CONVECTIVE AIR FLOW FOR COOLING ELEVATOR COMPONENTS, both of which are filed on even date with this application , and are incorporated by reference.

BACKGROUND OF THE INVENTION This invention relates to elevators. In particular, the present invention relates to a thermal management system using thermoelectric cooling to maintain elevator drive circuitry and motors in a desired operating temperature range.

This invention relates to elevator systems. In particular, the present invention relates to a thermal management system using thermoelectric heating and cooling to maintain components of an elevator system in a desired operating temperature range. Ambient conditions for an elevator system may range, for example, from above 0⁰C to about 45°C, with humidity ranging up to 95%. Components of the elevator system may be located in the machine room or the hoistway or the system, where the temperature can vary even more because these locations are not air-conditioned. Conventionally, air-cooling using fans has been used to cool components of an elevator system, such as the hoist motor and power electronics used to drive the elevators. This passive cooling with fans has limited effectiveness, and also creates a noise source that requires additional noise suppression. BRIEF SUMMARY OF THE INVENTION

An elevator system includes a drive system for driving an elevator and a thermoelectric temperature management system that cools components of the drive system, such as drive electronics and hoist motors.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an elevator system including a thermoelectric temperature management system for maintaining drive system components within a desired temperature range. FIG. 2A and 2B shows a thermoelectric temperature management system with thermoelectric devices in direct contact with elevator drive components for cooling and heating, respectively. FIGS. 3A and 3B show a thermoelectric thermal management system in which thermoelectric devices cool or heat an air stream, respectively, to control temperature of elevator drive components.

DETAILED DESCRIPTION FIG. 1 shows elevator system 10, which includes elevators 12a, 12b, and 12c. Each elevator 12a-12c includes elevator cab 14a-14c, counterweights 16a-16c, and hoist motors 18a-18c, respectively. Electrical power to operate elevators 12a-12c is provided by power system 20. While three elevators 12a-12c are shown in FIG. 1 , elevator system 10 can include any number of elevators, including only one. Power system 20 includes three-phase AC power supply 22, power converter 24, DC bus 26, smoothing capacitors 28a, 28b, and 28c, power inverters 30a, 30b, and 30c, controller 32, electrical energy storage (EES) system 34, bi-directional DC/DC converter 35 and dynamic brake 36. Three-phase AC power supply 20, which may be a commercial power source, provides electrical power to power converter 24. Power converter 24 is a three-phase power inverter that is operable to convert three-phase AC power from power supply 22 to DC power. In one embodiment, power converter 24 includes a plurality of power transistor circuits. Controller 32 controls the power transistor circuits to rectify the three-phase AC power from power supply 22 to DC power output that is supplied onto DC bus 26. While power supply 22 is shown as a three-phase power supply, power system 20 may be adapted to receive power from any type of power source, including a single phase AC power source and a DC power source.

Controller 32 monitors voltage across DC bus 26 with a voltage sensor or an overvoltage detection circuit, to assure the voltage across bus 26 does not exceed a threshold voltage level. This threshold level, which may be programmed into controller 32, is set to prevent overloading of components on power system 10. if the voltage across DC bus 26 exceeds the threshold level, controller 32 activates dynamic brake 46 to allow current flow through a dynamic brake resistor or resistors. This causes excess energy on DC bus 26 to be dissipated as heat.

Power inverters 30a-30c are three-phase power inverters that are operable to invert DC power from DC bus 26 to three-phase AC power. Power inverters 30a-30c may comprise a plurality of power transistor circuits that are controlled by controller 32. The three-phase AC power at the outputs of power inverters 30a-30c is provided to hoist motors 18a-18c of elevators 12a-12c, respectively.

The power transistor circuits of power invertors 30a-30c are also operable to rectify power that is generated when elevators 12a-12c drive their respective hoist motors 18a-18c. For example, if hoist motor 18a of elevator 12a is generating power, controller 32 controls the transistor circuits of power inverter 30a to allow the generated power to be rectified and provided to DC bus 26. Smoothing capacitors 28a-28c smooth the rectified power provided by power inverters 30a-30c on DC bus 26.

Hoist motors 18a-18c control the speed and direction of movement between respective elevator cabs 14a-14c and counterweights 16a-16c. The power required to drive each hoist motor 18a-18c varies with the acceleration and direction of elevators 12a-12c respectively, as well as the load in elevators 12a-12c, respectively. For example, if elevator 12a is being accelerated, run up with a load greater than the weight of counterweight 16a, or run down with a load less than the weight of counterweight 16a, a maximal amount of power is required to drive hoist motor 18a. If elevator 12a is leveling or running at a fixed speed with a balanced load, it may be using a lesser amount of power. If elevator 12a is being decelerated, running down with a heavy load, or running up with a light load, elevator 12a drives hoist motor 18a. In this case, hoist motor 18a generates three-phase AC power that is converted to DC power by power inverter 30a under the control of controller 32. The converted DC power is accumulated on DC bus 26.

Power system 20 may also include electrical energy storage (EES) system 34, which is connected to DC bus 26 through DC/DC converter 35 for conditioning the input power to EES 34. EES 34 includes battery storage modules, and may also include capacitive storage modules, together with switching circuitry to control charging and discharging of the storage modules. EES 34 stores excess energy output from power converter

24 and from power inverters 30a-30c during periods of negative power demand by hoist motors 18a-18c (i.e. regenerative mode). The energy stored in EES 34 may be used to power hoist motors 18a-18c during periods of positive power demand (i.e. motoring mode). The use of capacitive storage modules in parallel with battery storage modules within EES 34 can provide a current boost during periods of peak power demand by hoist motors 18a-18c.

Controller 32 provides control signals to EES 34 to manage the power stored in EES 34. During periods of positive power demand, controller 32 allows power stored in EES 34 to be available on DC bus 26. During periods of negative power demand, controller 32 allows excess power on DC bus 26 to be stored in EES 34.

By incorporating EES 34 into power system 20, several advantages are realized. Storing excess energy generated during periods of negative power demand on hoist motors 18a-18c avoids the loss of energy associated with converting the power on DC bus 26 to three- phase AC power through power converter 24. The demand on power supply 22 is reduced by the storage capacity of EES 34, resulting in reduction of the size and rating of the converter 24. In the event of a power failure or malfunction of power supply 22, energy stored in EES 34 may be used to power hoist motors 18a-18c for limited emergency and rescue operation of elevators 12a-12c.

Although the system benefits from the EES in various ways, the EES is not a necessary component enabling the deployment of the thermal management device in this invention. In other embodiments with no EES, the power from DC bus 26 is conditioned by a bi-directionaf DC/DC converter for powering the thermoelectric device 36.

Elevator system 10 also includes thermal management system 38, which cools (or heats) hoist motors 18a-18c, power inverters 30a-30c, and power converter 24 to maintain them within a desired operating temperature range. Thermal management system 38 includes thermoelectric (TE) heater/cooier 40, thermoelectric (TE) temperature management controller 42, ambient temperature sensor 44, motor temperature sensor 46 and inverter temperature sensors 48.

The ambient conditions for an elevator within system 10 may range, for example, from below 0°C to about 45°C, with humidity up to 95%. Hoist motors 18-18c, power inverters 30a-30c, and converter 24 can be located in the machine room or the hoistway of elevator system 10, where the temperature may vary even more because those locations are not air-conditioned.

Local temperature control of hoist motors 18a-18c and power inverters 30a-30c is provided by a thermal management system 38. As will be illustrated by FIGS. 2A-2B and 3A-3B, TE heater/cooler 40 may include thermoelectric elements directly in contact with hoist motors 18a-18c and power inverters 30a-30c, or may indirectly heat or cool hoist motors 18a-18c and power inverters 30a-30c by heating or cooling air that is directed onto them. TE heater/cooler 40 can also include heat pipes, heat sinks, and other heat exchangers in conjunction with the thermoelectric elements to cool or heat motors 18a-18c and inverters 30a- 30c. In another embodiment, the thermoelectric elements are used in conjunction with cool air and warm air ducts as described in the copending application entitled THERMOELECTRIC TEMPERATURE CONTROL WITH CONVECTIVE AIR FLOW FOR COOLING ELEVATOR COMPONENTS.

Control of TE heater/cooler 40 is performed by TE controller 42 as a function of sensed ambient temperature, sensed local temperatures of hoist motors 18a-18c, and sensed local temperatures of power inverters 30a-30c. TE heater/cooler 40 is operated by DC power provided by DC bus 26. The direction of current flow through the TE elements of TE heater/cooler 40 determines whether heater/cooler 40 operates in a heating or in a cooling mode. The operating mode is determined by TE controller 42 based upon inputs that include ambient temperature, the motor, and inverter local temperatures. The use of TE heater/cooler 40 provides a very small footprint for the thermal management system 38. TE heater/cooler 40 is capable of extremely fast response, and can provide both heating (if necessary) and cooling with the same device. TE heater/cooler 40 may include one or more thermoelectric modules for each component (motors 18a-18c and inverters 30a-30c), or several components may be cooled using the same thermoelectric module(s).

TE heater/cooler 40 also can function as a dehumidifier. As a result, moisture could otherwise condense on the surface of hoist motors 18a-18c and power inverters 30a-30c can be reduced, so that heat transfer between those components and the ambient environment is enhanced.

FIGS. 2A and 2B schematically illustrate an embodiment of TE heater/cooler 38 which provides direct cooling or heating to drive system components (i.e. motors 18a-18c or inverters 30a-30c). FIG. 2A shows operation in a cooling mode, while FIG. 2B shows operation in heating mode. In FIGS. 2A and 2B, TE device 50a is placed in direct contact with hoist motor 18a while TE device 50b is placed in contact with power inverter 30a. Each TE device 50a and 50b includes a series of alternating N type and P type semiconductor elements. The N type and P type elements are connected so that current will flow in a serpentine path as illustrated in FIGS. 2A and 2B. The direction of current flow will determine whether heat flows from hoist motor 18a and power inverter 30a toward TE elements 50a and 50b, respectively (as shown in FiG. 2A), or heat flows from elements 50a and 50b toward hoist motor 18 and power inverter 30a (as shown in FIG. 2B). In both cases, air stream 56 is directed between elements 50a and 50b, as shown in FIGS. 2A and 2B. TE heater/cooler 38 also includes fan 54, which provides air stream 56 that flows past thermoelectric elements 50a and 50b.

The heating and cooling produced by TE elements 50a and 50b is based upon the thermal flow that occurs within each of the N type and P type semiconductor elements. Movement of free charge carriers causes thermal flow within a semiconductor material. An N type material, the free charge carriers are electrons. In P type semiconductors, the free charge carriers are holes. Thus, thermal flow will be in the opposite direction to current flow in N type material, and will be in the same direction as current flow in P type material.

In FIG. 2A, current flows in the N type elements toward hoist motor 18a and power inverter 30a. This figure is for illustration purpose. The motor and power inverter and converter are not required to be physically located next to each other. Current flows in the P type elements in a direction away from the hoist motor 18a and power inverter 30a. As a result, both electrons in the N type elements and holes in the P type elements flow away from hoist motor 18a and power inverter 30a. A thermal gradient is produced in a direction away from hoist motor 18a and power inverter 30a and toward air stream 56.

In FIG. 2B, which illustrates heating of hoist motor 18a and power inverter 30a, the direction of current flow is reversed from that shown in FIG. 2A. Current flows in P type elements toward hoist motor 18a and power inverter 30a and flows toward hoist motor 18a and power inverter 30a in N type elements. As a result, a thermal gradient is produced in a direction toward hoist motor 18a and power inverter 30a and away from air stream 56.

FIGS. 3A and 3B show another embodiment of TE heater/cooler 36 in which TE elements 50a and 50b are positioned in air stream 56 produced by fan 54. Air stream 56, after heating or cooling by TE elements 50a and 50b, flows past hoist motor 18a and power inverter 30a.

In FIG. 3A, the current flow in elements 50a and 50b causes electrons in the N type elements and holes in the P type elements to move away from air stream 56 that is passing between elements 50a and 50b. As a result, thermal gradients are produced in a direction away from air stream 56, so that air stream 56 is cooled by elements 50a and 50b. As air stream 56 flows past hoist motor 18a and power inverter 30a, heat is transferred from hoist motor 18a and power inverter 30a to air stream 56, causing them to be cooled.

In FIG. 3B, the direction of current flow in elements 50a and 50b is reversed from the direction shown in FIG. 3A. Holes in P type elements and electrons in N type elements move toward air stream 56. As a result, a thermal gradient is produced and heat flows from elements 50a and 50b to air stream 56. As air stream 56 then passes hoist motor 18a and power inverter 30a, it transfers heat, thereby causing the ^• temperature of hoist motor 18a and 30a to be increased.

The examples shown in FIGS. 2A, 2B, 3A and 3B are intended to show the operating principles of direct and indirect cooling and heating with TE elements. The particular layout of hoist motors 18a- 18c and power inverters 30a-30c will dictate whether more than one drive component can be cooled/heated with a single TE module. In addition, in some cases only hoist motors 18a-18c or power inverter 30a-30c may be subject of thermoelectric thermal management, or other drive components that are adversely affected by extreme temperatures may be cooled or heated by thermal management system 38. In some cases, only cooling is required, since the drive components generate heat when they are operating. The TE thermal management system for the drive system of an elevator maintains the drive components in a temperature controlled environment. As a result, the drive components are not subjected to extreme operating temperatures that could cause premature failure.

By the use of thermoelectric devices to provide local temperature control, TE thermal management system 38 is capable of providing thermal management of the drive system components in locations such as the machine room or the hoistway which are not air conditioned. The benefits of the TE thermal management system include a very small footprint, extremely fast response, and the ability to perform multiple functions (heating and cooling) with the same device.

By maintaining a lower operating temperature for hoist motors 18a-18c, power inverters 30a-30c, and power converter 24, these components can have a higher power rating or a size reduction. In addition, thermal management system 38 offers a noise reduction compared to the fan systems that have been used for cooling. The lower operating temperature can also result in a reliability extension for the components, such as the power electronics of inverters 30a-30c.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that. changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. An elevator system comprising: an elevator; a drive system for driving the elevator; and a thermoelectric thermal management system for controlling an ambient condition of the drive system.

2. The elevator system of claim 1 wherein the thermoelectric thermal management system includes a thermoelectric device positioned to condition an air stream directed to a component of the drive system.

3. The elevator system of claim 1 wherein the thermoelectric thermal management system includes a thermoelectric device having a working surface in contact with a component of the drive system.

4. The elevator system of claim 1 wherein the thermoelectric thermal management system cools a hoist motor of the drive system.

5. The elevator system of claim 1 , wherein the thermoelectric management system cools drive circuitry of the drive system.

6. The elevator system of claim 1 wherein the drive circuitry includes a power inverter that converts DC power to AC power that operates the drive system and a converter that converts AC power to DC power.

7. The elevator system of claim 1 wherein the thermoelectric thermal management system controls temperature of the drive system as a function of at least one sensed parameter.

8. The elevator system of claim 7, wherein the sensed parameter comprises temperature of a component of the drive system.

9. The elevator system of claim 7, wherein the sensed parameter comprises ambient temperature.

10. The elevator system of claim 1 , wherein the thermoelectric thermal management system comprises: a thermoelectric heater/cooler; a temperature sensor for providing a temperature signal; and a controller for controlling operation of the thermoelectric heater/cooler as a function of the temperature signal.

11. A method of thermally managing a drive system component of an elevator system, the method comprising: sensing temperature of the drive system component, and controlling operation of a thermoelectric heater/cooler as a function of sensed temperature of the drive system component to maintain the drive system component system in an operating temperature range.

12. The method of claim 11 and further comprising." sensing ambient temperature; and controlling operation of the thermoelectric heater/cooler as a function of sensed ambient temperature and sensed temperature of the drive component.

13. The method of claim 11 wherein the drive system component comprises a hoist motor.

14. The method of claim 11 , wherein the drive component comprises drive circuitry.

15. The method of claim 14, wherein the drive circuitry comprises a power inverter and a power converter.

16. An elevator system comprising: a hoist motor, regenerative drive circuitry for delivering electrical energy to the hoist motor when the hoist motor is acting as a motor and delivering electrical energy from the hoist motor to an electric storage device when the hoist motor is operating as a generator; a thermoelectric heater/cooler for controlling temperature of at least one of the hoist motor and the regenerative drive circuitry.

17. The elevator system of claim 16 and further comprising: a controller for controlling the thermoelectric heater/cooler

^" as a function of sensed temperature.

18. The elevator system of claim 17, wherein the sensed temperature comprises ambient temperature.

19. The elevator system of claim 17, wherein the sensed temperature comprises temperature of the hoist motor.

20. The elevator system of claim 17, wherein the sensed temperature comprises temperature of the regenerative drive circuitry.