Electric motor controller for high-moisture applications and method of manufacture

An electric motor control system and methods of manufacture are provided. The system includes a power supply module including a printed circuit board (PCB) and a plurality of power processing components configured to convert an input voltage into an output voltage. The system also includes a motor management module including an encapsulated, heat-sharing package for housing a plurality of moisture-sensitive driver components configured to convert the output voltage from the power supply module and provide output voltages for application to windings of the electric motor.

BACKGROUND

The field of the invention relates generally to electric motor control systems, and more particularly, to moisture penetration protection for electric motor control systems used in high-moisture applications.

Electric motors are being utilized in a plurality of different heating, ventilation, and air conditioning (HVAC) applications (furnaces, heat pumps and air conditioners) with acceptable records of reliability. Although the reliability of electric motors has steadily increased through the years, there is an industry need for a moisture resistant electric motor to meet an increasing demand for longer warranties (e.g., from 1 year to 5-10 years). Moisture penetration is a leading cause of failures in electronic components of motor control systems, particularly in air conditioners and heat pumps where high-level humidity level typically occurs. Connectivity (e.g., integrity of signal connectors) is another leading cause of failures.

Present packaging processes in at least some known motor control systems include printed circuit board (PCB) mounted electronic components and cable connections for power and signal lines. Surface-mount thick film resistors used in the motor control systems are very sensitive to moisture penetration. When moisture penetrates the hardware electronics, silver migration at resistor terminals occurs and causes a resistance drop, resulting in a short circuit or disconnection. The connectors used for the power lines and the signal lines also provide a moisture penetration path, which impacts the overall moisture level of motor drive electronics inside the enclosure. In general, power lines of the motor control system input and connections carry higher current levels when the motor is running, so the resistive loss produced by the cable itself may reduce the surrounding moisture level. However, signal connections between the electric motor and the HVAC system controller typically carry very low current, so it cannot reduce the level of surrounding moisture. As a result, moisture penetrates the low power signal-level circuit, which includes numerous moisture sensitive components, and eventually results in a failure. As such, the known PCB-based packaging techniques do not provide a solution to moisture ingress over the desired warranty time, which causes field failures and additional expenses for consumers and motor suppliers.

BRIEF DESCRIPTION

In one aspect, an electric motor control system is provided. The system includes a power supply module including a printed circuit board (PCB) and a plurality of power processing components configured to convert an input voltage into an output voltage. The system also includes a motor management module including an encapsulated, heat-sharing package for housing a plurality of moisture-sensitive driver components configured to convert the output voltage from the power supply module and provide output voltages for application to windings of the electric motor.

In another aspect, a method of manufacturing an electric motor control system configured to be coupled to an electric motor is provided. The method includes coupling a plurality of power processing components to a printed circuit board (PCB) to form a power supply module. The power processing components are configured to convert an input voltage into an output voltage. The method also includes coupling a plurality of moisture-sensitive driver components within an encapsulated, heat-sharing package to form a motor management module. The moisture-sensitive driver components are configured to convert the output voltage from the power supply module and provide output voltages for application to windings of the electric motor. The method further includes electrically coupling the power supply module to the motor management module using high-voltage wires.

DETAILED DESCRIPTION

FIG. 1is an exploded view of an exemplary electric motor10. Motor10includes control system11, a stationary assembly12including a stator or core14, and a rotatable assembly16including a rotor18and a shaft20. In the exemplary embodiment, motor10is utilized as a fan and/or blower motor in a fluid (e.g., water, air, etc.) moving system. For example, electric motor10may be utilized in a clean room filtering system, a fan filter unit, a variable air volume system, a refrigeration system, a furnace system, an air conditioning system, and/or a residential or commercial heating, ventilation, and air conditioning (HVAC) system. Alternatively, motor10may be implemented in any application that enables motor10to function as described herein. Motor10may also be used to drive mechanical components other than a fan and/or blower, including mixers, gears, conveyors, and/or treadmills. In the exemplary embodiment, control system11is integrated with motor10. Alternatively, motor10may be external to and/or separate from control system11.

Rotor18is mounted on and keyed to shaft20journaled for rotation in conventional bearings22. Bearings22are mounted in bearing supports24integral with a first end member26and a second end member28. End members26and28have inner facing sides30and32between which stationary assembly12and rotatable assembly16are located. Each end member26and28has an outer side34and36opposite its inner side30and32. Additionally, second end member28has an aperture38for shaft20to extend through outer side34.

Rotor18comprises a ferromagnetic core40and is rotatable within stator14. Segments42of permanent magnet material, each providing a relatively constant flux field, are secured, for example, by adhesive bonding to rotor core40. Segments42are magnetized to be polarized radially in relation to rotor core40with adjacent segments42being alternately polarized as indicated. While magnets on rotor18are illustrated for purposes of disclosure, it is contemplated that other rotors having different constructions and other magnets different in both number, construction, and flux fields may be utilized with such other rotors within the scope of the invention.

Stationary assembly12comprises a plurality of winding stages44adapted to be electrically energized to generate an electromagnetic field. Stages44are coils of wire wound around teeth46of laminated stator core14. Winding terminal leads48are brought out through an aperture50in first end member26terminating in a motor connector52. While stationary assembly12is illustrated for purposes of disclosure, it is contemplated that other stationary assemblies of various other constructions having different shapes and with different number of teeth may be utilized within the scope of the invention.

Motor10further includes an electronics enclosure54which mounts on the rear portion of motor10to house control system11. Electronics enclosure54and control system11may sometimes be referred to collectively as a motor control assembly55. Electronics enclosure54includes a bottom wall56and a substantially annular side wall57. Control system11includes a plurality of electronic components58and a connector59mounted within electronics enclosure54. Control system11is connected to winding stages44by interconnecting motor connector52. Control system11applies a voltage to one or more of winding stages44at a time for commutating winding stages44in a preselected sequence to rotate rotatable assembly16about an axis of rotation. In an alternative embodiment, control system11is remotely positioned from and communicatively coupled to motor10. In another alternative embodiment, control system11is a central control system for more than one electric motor (e.g., in an HVAC system), and is communicatively coupled to motor10.

A casing72is positioned between first end member26and second end member28to facilitate enclosing and protecting stationary assembly12and rotatable assembly16.

FIG. 2is a block diagram of an exemplary motor control assembly55(shown inFIG. 1) for controlling operation of electric motor10including a motor management module for reducing moisture damage to signal components.FIG. 3is a perspective view of motor control assembly55including the motor management module.FIG. 4is an exploded perspective view of motor control assembly55.FIG. 5is an assembled view of motor control assembly55coupled to motor10. In the exemplary embodiment, motor control assembly55includes electronics enclosure54, which houses control system11. Control system11includes a power supply module200and a motor management module210that is physical separate from, but in electrical communication with power supply module200.

Power supply module200includes an input connector201a plurality of electrical components202, and an output connector203mounted on a component board, such as a printed circuit board (PCB)204. Power supply module200integrates large through-hole electrical components and power connectors of control system11that are not sensitive to moisture. In the exemplary embodiment, PCB204is coupled to an interior surface of bottom wall56of electronics enclosure54.

In the exemplary embodiment, input connector201includes power input line connectors205for coupling to a power source206. Input connector201interfaces with and receives input power from power source206via an opening in side wall57of electronics enclosure54. In some embodiments, power is supplied via a system controller220, such as an HVAC system controller.

Electrical components202of power supply module200are configured to convert input voltage received from power source206to a desired level of direct current (DC) voltage. Using output connector203, power supply module200outputs the converted DC voltage to motor management module210. Output connector203includes two high-voltage wires208for providing the converted DC voltage to motor management module210.

Motor management module210includes an input/output connector211and electrical components (shown inFIG. 8). Motor management module210houses moisture-sensitive electrical components of control system11within an encapsulated, heat-sharing package212that provides protection from damage and/or failure due to moisture entering electronics enclosure54, as described in more detail herein.

Heat-sharing package212includes an insulated metal substrate213coupled to a metal heatsink214formed in side wall57of electronics enclosure54. For example, heat-sharing package212may include an insulated metal substrate (IMS) or a thick printed copper (TPC) based packaging to integrate high power semiconductor devices and all moisture-sensitive components such as integrated circuits and surface mount resistors. Heat generated by electrical losses of the semiconductor devices causes the elements mounted on the heat sharing package to operate at relatively higher temperatures. The higher operating temperatures cause moisture near the motor management module210to evaporate.

Heat-sharing package212includes a minimization of external connections. Included in connections to the external environment are the power connections (which naturally tend to be moisture resistant). These power connections include the DC power from power supply module200and the three phase AC power to motor10. To provide the desired minimization of connections, the signal connections are made via a wireless connection to system controller220. Heat-sharing package212includes an insulated metal substrate with an over-molded cover that is selected to substantially make a water tight protection of the interior components. Heat-sharing between the power transistors and the signal components is assured by the close proximity of these components and the common heat spreader of the metal portion of the metal insulated substrate which lies under all the components. It is this heat-sharing that is being relied on to aid in the exclusion of moisture that could eventually be taken up by the low level voltage signal circuitry.

Motor management module210including power semiconductors (IGBTs, MOSFETs or other) mounted on heatsink214and other components generate heat as they switch power to the motor windings. Electric losses of other switching elements such as the DC/DC converter also contribute to elevate the temperature of the package. The high operating temperature of heat-sharing package212evaporates standing water on motor management module210, thus preventing water from penetrating inside motor management module210.

Input/output connector211is coupled to high-voltage wires208for receiving the converted DC voltage from power supply module200. Motor management module210converts the DC voltage to a three-phase alternating current (AC) voltage for driving electric motor10based in instructions received from an external device, for example, an HVAC system controller. Input/output connector211outputs the three-phase AC voltage to winding stages44of motor10via output power wires215.

In the exemplary embodiment, an external communications module230is communicatively coupled to motor management module210as well as system controller220. More specifically, in the exemplary embodiment, external communications module230is removably couplable to system controller220using a communication wire, and is communicatively coupled to motor management module210using wireless communication. However, external communications module230may also be communicatively coupled to system controller220using wireless communication. Alternatively, in some embodiments, external communications module230is integral to system controller220. External communications module230is controlled by a user, such as an original equipment manufacturer (OEM), and enables control of motor operation by transmitting control signals to system controller220and/or motor management module210.

FIG. 6is a block diagram of an exemplary power supply module200(shown inFIGS. 2-4) configured to receive input power from an AC power source. In the exemplary embodiment, power supply module200is configured to receive AC power from power source260. For example, in the exemplary embodiment, power source206is an AC utility or mains600that provides single-phase AC input voltage of 120V/240V/277V at 50/60 Hz.

In the exemplary embodiment, power supply module200includes input connector201for connecting to mains600, an inrush limiter602for inrush current protection, an electromagnetic interference (EMI) filter604for reducing EMI, a rectifier606for converting AC voltage from mains600to DC voltage, a transient voltage protection device608for lightning or power surge protection of rectifier606, at least one DC-link capacitor610to minimize voltage transients experienced during power switch operation, and output connector203to provide the resulting DC voltage to motor management module210.

FIG. 7is a block diagram of an exemplary power supply module200(shown inFIGS. 2-4) configured to receive input power from a DC power source. In the exemplary embodiment, power supply module200is configured to receive DC power from power source206. For example, in the exemplary embodiment, power source206is a micro-grid or nano-grid700that provides DC input voltage of about 380V.

In the exemplary embodiment, power supply module200includes input connector201for connecting to DC grid700, an inrush limiter702for inrush current protection, a reverse protector703for providing protection from wire misconnection, an electromagnetic interference (EMI) filter704for reducing EMI, at least one DC-link capacitor706configured to provide local protection from switching transients caused by power switch operation, a transient voltage protection device708for lightning or power surge protection in DC-link capacitor706, and output connector203to provide the resulting DC voltage to motor management module210.

FIG. 8is a block diagram of an exemplary motor management module210(shown inFIGS. 2-4). In the exemplary embodiment, motor management module210includes input/output connector211for receiving the DC voltage from power supply module200, power semiconductor switches800for switching the DC power to the motor phases as AC power, a microcontroller802for implementing an algorithm to control one or more gate drivers804to operate power semiconductor switches800, a low voltage power supply806and associated internal circuitry for providing low voltage power to microcontroller802from a higher voltage that is applied to entire motor management module210, and input/output connector211for coupling to motor winding stages. In the exemplary embodiment, low voltage power supply806is a DC-DC converter that supplies low voltage sources to microcontroller802and to a wireless communications module808.

In the exemplary embodiment, motor management module210also includes a plurality of sensors810for providing data to microcontroller802. Sensors810are configured to measure various operating parameters associated with the operation of motor10, including voltage measurements, current measurements, temperature measurements, vibration measurements, and/or any other known measurements associated with operating an electric motor or the operating environment. Sensors810are contained within heat-sharing package212and do not require penetration out of package212, which would create potential for moisture penetration.

In the exemplary embodiment, motor management module210further includes wireless communication module808for communicating with an external device to receive a motor control command signal, which is used by microcontroller802to switch power semiconductor switches800to drive motor10at an appropriate level. Wireless communication module808communicates with one or more remote devices, such as external devices. In the exemplary embodiment, wireless communication module808converts a received wireless signal into a control signal that microcontroller802utilizes to control operation of electric motor10. Wireless signals may include, but are not limited to, Bluetooth, Bluetooth low energy, near field communications (NFC), infrared, and/or any other known types of wireless signals. Using wireless communication to communicate with external devices enables elimination of hardwired communication connectors. Such hardwired connectors are a common entry point for moisture, so their removal makes motor10more resistant to moisture.

In some embodiments, casing72and/or electronics enclosure54are manufactured using metal, which may interfere with wireless signals being transmitted to microcontroller802. As such, motor management module210may be positioned adjacent to an opening814defined in casing72or electronics enclosure54. Motor management module210includes an antenna812within the over-molded portion of heat-sharing package212such that a wireless signal entering electronics enclosure54via opening814penetrates package212and is received by antenna812. Antenna812enables wireless communication between a user of motor10(i.e., a manufacturer of motor10, an HVAC system manufacturer using motor10, a technician of motor10, and/or a customer owning motor10) with microcontroller802to define, change, or override the operating parameters stored in a microcontroller memory device. Positioning antenna812adjacent to opening814enables wireless signals to be received by antenna812and transmitted to microcontroller802.

As described above, motor management module210includes heat-sharing package212, which is formed of an insulated metal substrate. During operation, heat generated by electrical losses of power semiconductor switches800causes low power circuits to operate at relatively higher temperatures. The higher operating temperatures cause moisture near the motor management module210to evaporate, thus providing additional moisture protection for motor management module210.

In the exemplary embodiment, microcontroller802includes at least one memory device816and a processor818that is communicatively coupled to memory device816for executing instructions. In some embodiments, executable instructions are stored in memory device816. In the exemplary embodiment, microcontroller802performs one or more operations described herein by programming processor818. For example, processor818may be programmed by encoding an operation as one or more executable instructions and by providing the executable instructions in memory device816.

Processor818may include one or more processing units (e.g., in a multi-core configuration). Further, processor818may be implemented using one or more heterogeneous processor systems in which a main processor is present with secondary processors on a single chip. As another illustrative example, processor818may be a symmetric multi-processor system containing multiple processors of the same type. Further, processor818may be implemented using any suitable programmable circuit including one or more systems and microcontrollers, microprocessors, reduced instruction set circuits (RISC), application specific integrated circuits (ASIC), programmable logic circuits, field programmable gate arrays (FPGA), and any other circuit capable of executing the functions described herein. In the exemplary embodiment, processor818controls operation of microcontroller802.

In the exemplary embodiment, memory device816is one or more devices that enable information such as executable instructions and/or other data to be stored and retrieved. Memory device816may include one or more computer readable media, such as, without limitation, an NFC electrically erasable programmable read-only memory (EEPROM), a standard EEPROM, dynamic random access memory (DRAM), static random access memory (SRAM), a solid state disk, and/or a hard disk. Memory device816may be configured to store, without limitation, application source code, application object code, source code portions of interest, object code portions of interest, configuration data, execution events and/or any other type of data. In the exemplary embodiment, memory device816includes firmware and/or initial motor configuration data for microcontroller802. Moreover, in the exemplary embodiment, memory device816stores diagnostic data associated with operation of motor10, for transmission to one or more external devices upon request. Diagnostic data includes, but is not limited to including, time powered, time run, time run above 80% demand, time in speed cutback region, time in temperature cutback region, good starts, failed starts, resets, stalls, number of bad serial packets received, watchdog shutdown events, time run in certain demand ranges, thermal shock events, power module temperature, bus voltage, open-phase events, UL lockouts, reverse start attempts, shaft watts, and torque.

FIG. 9is a block diagram of system controller220and external communications module230(shown inFIG. 2). In the exemplary embodiment, external communications module230includes an antenna900, a wireless module902, an interface circuit904, and a low power supply906which outputs 3.3V to power wireless module902. Interface circuit904translates signals between system controller220and wireless module902, and also receives power (24V AC) from system controller220.

FIG. 10is a block diagram showing communications between system controller220and motor10via external communications device230. In the exemplary embodiment, system controller220transmits a motor command signal to motor10. More specifically, in the exemplary embodiment, system controller220transmits a motor command signal via wireless module902. Wireless module808of motor management module210receives the motor command signal and operates power switches800to drive motor10in accordance with the motor command signal.

In one embodiment, motor10is used in a residential HVAC application, such as an air conditioner, a heat pump, and/or a furnace. System controller220is an OEM system controller with a thermostat. External communications device230enables communications between the OEM system controller and the thermostat, and wireless module808(shown inFIG. 8) of motor management module210. A user selects a mode of operation on the OEM system controller (i.e., heating, cooling, or continuous fan). The thermostat measures and provides a temperature to the OEM system controller. Based on the selected mode of operation and the measured temperature, the OEM system controller transmits a motor command signal to motor10. More specifically, in the exemplary embodiment, the OEM system controller transmits a motor command signal via wireless module902. Wireless module808of motor management module210receives the motor command signal and operates power switches800to drive motor10in accordance with the motor command signal.

In another embodiment, system controller220is an external programming device that includes external communications device230. The external programming device is a mobile computing device such as a smartphone, a tablet, or a laptop computer, and enables a user such as an OEM or a technician to configure, program, collect diagnostic information from, and/or perform field commissioning on motor10. External communications device230enables communications between the external programming device and wireless module808(shown inFIG. 8) of motor management module210. The external programming device monitors the building environment and transmits motor command signals to motor10. More specifically, in the exemplary embodiment, the external programming device transmits a motor command signal via wireless module902. Wireless module808of motor management module210receives the motor command signal and operates power switches800to drive motor10in accordance with the motor command signal.

The motor control system and methods described herein provide a two-module packaging design for the motor control system of an electric motor, particularly in HVAC applications. More specifically, a power supply module uses common printed circuit board (PCB) technology to integrate large through-hole electronic components and power connectors that are not sensitive to moisture. A motor management module uses an encapsulated, heat-sharing package to integrate high-power semiconductor devices and all moisture sensitive components such as ICs and surface mount resistors. The motor management module also eliminates all signal connectors for external communications devices by using wireless technology to prevent the penetration path of moisture into the motor control system. Additionally, the encapsulated, heat-sharing package provides additional moisture protection as heat generated by the plurality of moisture-sensitive driver components causes the low power supply to operate at a relatively higher temperature and evaporate moisture near the motor management module. By making the moisture-sensitive components less susceptible to moisture penetration and evaporating moisture near the motor management module, the motor control system and method described herein provide greater reliability and reduce the amount of electric motor failures due to moisture penetration, which results in decreased maintenance and operating expenses.

Some embodiments described herein relate to electric motors including electric motors and electronic controls. However, the methods and apparatus are not limited to the specific embodiments described herein, but rather, components of apparatus and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the methods may also be used in combination with any motor, and are not limited to practice with the electric motors as described herein. In addition, the exemplary embodiment can be implemented and utilized in connection with many other applications.

When introducing elements/components/etc. of the methods and apparatus described and/or illustrated herein, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the element(s)/component(s)/etc. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional element(s)/component(s)/etc. other than the listed element(s)/component(s)/etc.