Patent Description:
At least some electric machines include accelerometers and temperature sensors to periodically measure, for example, vibrations and ambient temperature around the electric machine. Such measurements can be useful in determining the amount of wear experienced by the electric machine over time as well as the general health of the electric machine. Some electric machines include piezo-electric accelerometers to measure vibration. Some electric machines include resistance temperature sensors (RTDs) embedded in circuitry of the electric machine to monitor temperature. Such sensors can be integrated into the electric machine and its housing, and are generally powered by batteries or otherwise supplied power independent of the electric machine itself. Some electric machines (electrically commutated motors, for example) include current sensors integrated onto a controller (e.g., a motor controller) for measuring stator currents to properly operate the electric machine. Other electric machines (induction motors, for example) do not need to measure stator currents to operate. Data collected by sensors can be used and stored locally on the electric machine and, more specifically, on a memory device integrated within the housing. Alternatively, the data collected by the sensors may be transferred to a remote memory device such as, for example, a mass storage device or a cloud server using wired or wireless communications. It is, however, desirable to improve the fidelity of electric machine health data without the expense of complex retrofitting.

<CIT> relates to a motor monitoring system that uses several calculated monitoring values to determine a status of a motor and take a predetermined action when a threshold corresponding with the monitoring value is exceeded. The threshold may be calculated by an intelligent electronic device (IED) monitoring the motor.

S <CIT> relates to a power supply that comprises at least one transformer placed around an active power line and connected through at least one power conditioning system to provide a conditioned power source for at least one electronic device.

<CIT> relates to multiphase electric machines and, more particularly, to a monitoring system for such machines that enables the identification of incipient failure modes.

<CIT> relates to monitoring electric current in electric power systems, and more particularly to a current monitoring device that derives its operating power from one or more electric current inputs.

<CIT> relates to condition monitoring systems and, in particular, to rotation detection sensors and condition monitoring system based on such sensors.

<CIT> relates to a method and apparatus for monitoring the condition of electric motors. More particularly, the invention relates to an electric motor integrated monitoring system for monitoring and recording various operating parameters during life of the motor to predict malfunctions and estimate motor life.

In one aspect, the invention provides a health monitor circuit for an electric machine, according to claim <NUM>.

In another aspect, the invention provides an electric machine according to claim <NUM>.

In yet another aspect, the invention provides a method of monitoring health of an electric machine, according to claim <NUM>.

Embodiments of the health monitor circuit described herein provide improved fidelity of electric machine health data without the expense of complex retrofitting. More specifically, health monitor circuits described herein include multiple sensors for detecting operating parameters and environmental conditions for the electric machine, including a current transformer. The current transformer enables, for example, both stator current measurement and energy harvesting for supplying power to the health monitor circuit itself. The combination of operating parameters and environmental conditions such as, for example, ambient temperature, ambient humidity, barometric pressure, and acceleration with stator current measurements enables improved analysis and monitoring of electrical and mechanical degradation, or "wear," experienced by the electric machine, and further enables inferences of various aspects of the health of the mechanical load (for electric motors) coupled to and driven by the electric motor, or the health of the machine coupled to and turning the rotor (for electric generators). The current induced by the stator current in the current transformer may be rectified and applied directly to components of the health monitor circuit, or to an energy storage device that supplies power to at least the health monitor circuit. The health monitor circuits described herein may further include voltage regulating and power distribution circuits for generating and supplying power to components of the health monitor circuit. The health monitor circuits described herein may further include current sense circuits that enable periodic collection and storage of stator current measurements (and other measurements of operating parameters and environmental conditions) controlled by a microprocessor or other suitable processing device. The health monitor circuits described herein may further include a communication interface for communicating measurements to a remote device, such as, for example, a system controller or other suitable computing system. Such a communication interface may include one or more wired communication channel or wireless communication channel.

<FIG> is a block diagram of an example electric machine <NUM> having a health monitor circuit <NUM>. Electric machine <NUM> is illustrated as an electric motor that includes a rotor <NUM> and a stator <NUM>. Rotor <NUM> is configured to be coupled to a mechanical load <NUM>. Mechanical load <NUM> may include, for example, a rotatable load such as a fan, wheel, blower, impeller, compressor, fly wheel, transmission, or crank shaft, among others. Mechanical load <NUM> may also include a linear load, such as a solenoid or linear actuator, among others. In alternative embodiments, rotor <NUM> is configured to be coupled to a machine that turns rotor <NUM> to operate electric machine <NUM> as an electric generator. Such a machine may include a combustion engine, gas turbine, wind turbine, steam turbine, or any other suitable machine for turning rotor <NUM>. Referring again to the embodiment of <FIG> in which electric machine <NUM> is an electric motor, stator <NUM> generally includes one or more stator windings (not shown) that, when energized and conducting stator current, are electromagnetically coupled to rotor <NUM> and cause rotor <NUM> to turn, on a longitudinal axis, with respect to stator <NUM>.

Electric machine <NUM> is supplied alternating current (AC) from an AC source <NUM>. AC source <NUM> may include, for example, an electrical grid, a diesel, wind, or turbine generator, or any other suitable AC source. AC source <NUM> may alternatively include one or more direct current (DC) sources having an output that is converted, or "inverted," to an AC power before being supplied to electric machine <NUM>. AC power from AC source <NUM>, in certain embodiments, may be applied directly to stator <NUM>. In alternative embodiments, electric machine <NUM> may be supplied AC or DC power that is appropriately converted to AC and/or DC by electric machine <NUM> itself. For this purpose, among others, some embodiments of electric machine <NUM> include a motor controller <NUM>. In other embodiments, motor controller <NUM> may be omitted.

Motor controller <NUM> generally includes one or more processors, one or more memory devices, and a drive circuit (all not shown). Generally, the drive circuit supplies electric power to stator <NUM> of electric machine <NUM> based on control signals received from the one or more processors. The drive circuit may include, for example, various power electronics for conditioning line frequency AC power to be supplied to the stator windings of electric machine <NUM> with a desired current, i.e., phase and amplitude, and frequency. Such power electronics may include, for example, and without limitation, one or more rectifier stages, power factor correction (PFC) circuits, filters, transient protection circuits, EMF protection circuits, inverters, or power semiconductors. Motor controller <NUM>, in certain embodiments, may include a communication interface (not shown). The communication interface may include one or more wired or wireless hardware interface, such as, for example, universal serial bus (USB), RS232 or other serial bus, CAN bus, Ethernet, near field communication (NFC), WiFi, Bluetooth, or any other suitable digital or analog interface for establishing one or more communication channels between motor controller <NUM> and a remote device <NUM>. Remote device <NUM> may include a system controller, smart phone, personal computer, mass storage system, cloud server, or any other suitable computing system. The communication interface may include, for example, a wired communication channel <NUM> to remote device <NUM> or an antenna <NUM> for establishing a wireless communication channel with remote device <NUM>. The communication interface further includes a software or firmware interface for receiving one or more control parameters and writing them, for example, to memory. In certain embodiments, the communication interface includes, for example, a software application programming interface (API) for supplying one or more parameters for operating electric machine <NUM>.

In alternative embodiments, the communication interface may be implemented independent of motor controller <NUM> such that it serves both motor controller <NUM> and health monitor circuit <NUM>. In a further alternative embodiment, the communication interface may be incorporated into health monitor circuit <NUM>.

Electric machine <NUM> may include a casing within which rotor <NUM> and stator <NUM> are located. Electric machine <NUM> may also include an electrical housing, or "conduit box," within which various electrical components of electric machine <NUM> may be located, such as, for example, motor controller <NUM> and health monitor circuit <NUM>.

<FIG> is a schematic diagram of health monitor circuit <NUM> for use in electric machine <NUM> shown in <FIG>. <FIG> further illustrates electric machine <NUM> being supplied AC power form AC source <NUM> to cause electric machine <NUM> and, more specifically, its rotor to operate mechanical load <NUM>. Health monitor circuit <NUM> includes an energy storage device <NUM>, a rectifier <NUM>, a voltage regulator <NUM>, a communication interface <NUM>, a plurality of sensors <NUM>, a microprocessor <NUM>, a current sense circuit <NUM>, a memory device <NUM>, and a current transformer <NUM>. In certain embodiments, memory device <NUM> is implemented internal to, or as a component of, microprocessor <NUM>. In other embodiments, memory device <NUM> is a separate component from microprocessor <NUM>.

Energy storage device <NUM> is configured to supply power to health monitor circuit <NUM>. More specifically, to the extent rectifier <NUM>, voltage regulator <NUM>, communication interface <NUM>, sensors <NUM>, microprocessor <NUM>, current sense circuit <NUM>, memory device <NUM>, and current transformer <NUM> require power to operate, such power is supplied by energy storage device <NUM>. Energy storage device <NUM> may include, for example, one or more capacitors. In alternative embodiments, the energy storage device may include one or more batteries. Current transformer <NUM> and energy storage device <NUM>, in at least some embodiments, do not supply a precise and stable voltage that is needed for many components of health monitor circuit <NUM>. Accordingly, energy storage device <NUM> supplies, for example, a DC voltage to voltage regulator <NUM>. In certain embodiments, energy storage device <NUM> is omitted, and power is supplied to health monitor circuit <NUM> directly from current transformer <NUM>, rectifier <NUM>, and voltage regulator <NUM>. Voltage regulator <NUM> generates a stable DC voltage that can be used by the various components of health monitor circuit <NUM>. For example, in certain embodiments, voltage regulator <NUM> generates a stable <NUM> Volts DC (VDC) supply. Alternatively, voltage regulator <NUM> may generate a stable <NUM> VDC supply or any other suitable regulated voltage for operating health monitor circuit <NUM>. Voltage regulator <NUM> supplies the desired DC voltage on a DC bus <NUM>, or "rail," that delivers the desired DC voltage the various components of health monitor circuit <NUM>.

Current transformer <NUM> is configured to be electromagnetically coupled to a stator winding <NUM> of electric machine <NUM>, of which electric machine may include one or more. More specifically, as illustrated in <FIG>, current transformer <NUM> is configured to be electromagnetically coupled to an electrical conductor <NUM>, bus, or wire, that supplies, or "feeds," stator current to stator winding <NUM> itself. The current conducting through electrical conductor <NUM> is generally assumed to be the stator current conducting through stator winding <NUM> itself. Current transformer <NUM> generally includes a primary winding, or "coil," and a secondary winding <NUM>. For the purpose of current measurement, the conductor through which current is being measured, i.e., electrical conductor <NUM>, is considered the primary winding. In certain embodiments, where current transformer <NUM> is "clamped" onto electrical conductor <NUM>, or the "primary winding," the primary winding includes a single "turn. " In alternative embodiments, where an inductive coil is utilized as a primary winding, the number of turns is simply accounted for (as a ratio of primary turns to secondary turns) in using, measuring, and interpreting the current induced in secondary winding <NUM>.

Current transformer <NUM> is coupled to energy storage device <NUM>, for example, through rectifier <NUM>. When stator current is conducted through stator winding <NUM>, an electromagnetic field is generated that induces a current in secondary winding <NUM>, producing an AC signal that is received and converted, or rectified, by rectifier <NUM> to a DC signal for charging energy storage device <NUM>. In alternative embodiments, energy storage device <NUM> is omitted and the DC signal produced by rectifier <NUM> is supplied directly to components of health monitor circuit <NUM> or voltage regulator <NUM>. In addition to enabling harvesting of energy from the electromagnetic field generated by the stator current, the induced AC signal is also measurable and represents a measure of the stator current itself. Current sense circuit <NUM> enables periodic polling, or collection, of a stator current measurement from current transformer <NUM>. Current sense circuit <NUM> includes, for example, amplifiers, switches, and other electrical components (not shown) to enable collection of measurements. For example, in certain embodiment, current sense circuit <NUM> includes a current sense amplifier that is configured to detect a voltage in a current measurement circuit, the voltage representing the current induced in secondary winding <NUM>. The amplifier then generates and transmits an analog stator current measurement signal that represents the current induced in secondary winding <NUM>. Additionally, current sense circuit <NUM> may include a switch coupled to current transformer <NUM> and, when commutated, closes the current measurement circuit to enable collection of the stator current measurement. The switch may be coupled directly or indirectly to current transformer <NUM>. For example, the switch may be coupled indirectly through one or more discrete electrical components (e.g., resistors, capacitors, inductors, etc.). The current measurement circuit may include, for example, a current sense resistor, across which a voltage is detected by the current sense amplifier.

Current sense circuit <NUM> is coupled to microprocessor <NUM>. Microprocessor <NUM> includes one or more processing devices coupled to memory device <NUM>. Memory device <NUM> stores, for example, computer-executable instructions, or program code, as well as measurements collected from current transformer <NUM> and other sensors <NUM>. Microprocessor <NUM> is configured by gaining access to and executing the computer-executable instructions, or program code, stored in memory device <NUM>. Alternatively, microprocessor <NUM> may be configured by similarly gaining access to program code or firmware stored in read-only memory (ROM), random access memory (RAM), or any other suitable storage medium for program code. Microprocessor <NUM> is configured control the switch within current sense circuit <NUM> by transmitting a control signal to the switch to commutate the switch to enable collection of the stator current measurement. In certain embodiments, microprocessor <NUM> is configured to generate and transmit the control signal to commutate the switch at a sampling frequency of at least a frequency of the stator current supplied to the stator winding, thereby enabling collection of a stator current measurement once per cycle of the AC power supplied to the stator winding. In one embodiment, for example, the AC signal supplied to the stator winding may be a common standard frequency of <NUM> Hertz or <NUM> Hertz. In alternative embodiments, the sampling frequency at which microprocessor <NUM> collects stator current measurements may be greater or fewer than once per AC cycle.

Microprocessor <NUM> is coupled to sensors <NUM> and is configured to periodically collect measurements from sensors <NUM>. Sensors <NUM>, in certain embodiments, may include an ambient temperature sensor, an ambient humidity sensor, a barometric pressure sensor, or an acceleration sensor, such as a microelectromechanical systems (MEMS) triaxial accelerometer. Sensors <NUM> may also include one or more current sensors in addition to current transformer <NUM>. Sensors <NUM> may include any other type of sensor or device for collecting analog or digital data from electric machine <NUM>. Sensors <NUM> are configured to monitor various operating parameters and environmental conditions of or around electric machine <NUM>. Sensors <NUM> may further enable monitoring of various operating parameters of mechanical load <NUM>, particularly when combined with stator current measurements collected from current transformer <NUM>. At least some of sensors <NUM> may be installed on electric machine <NUM> or, for example on motor controller <NUM>, and transmit measurement data back to microprocessor <NUM>.

Microprocessor <NUM> is coupled to memory device <NUM> and is configured to write measurements from current transformer <NUM> and sensors <NUM> to memory device <NUM>. In certain embodiments, memory device <NUM> is a separate component from microprocessor <NUM>. In alternative embodiments, memory device <NUM> is implemented as a component within microprocessor <NUM>. Microprocessor <NUM>, in certain embodiments, is also coupled to communication interface <NUM>. Communication interface <NUM> may include one or more wired or wireless hardware interface, such as, for example, universal serial bus (USB), RS232 or other serial bus, CAN bus, Ethernet, near field communication (NFC), WiFi, Bluetooth, Xbee, Zigbee, DigiMesh, cellular, RF, or any other suitable digital or analog interface for establishing one or more communication channels <NUM> between health monitor circuit <NUM> and, for example, remote device <NUM> (shown in <FIG>). Communication channels <NUM> may, in certain embodiments, be continuous, or persistent, communication channels or, alternatively, temporary, or transient, communication channels that are established when remote device <NUM> is within range or otherwise available to connect with communication interface <NUM>. Communication interface <NUM> may include, for example, a wired connection <NUM> to remote device <NUM> or an antenna <NUM> for establishing a wireless communication channel with remote device <NUM> (all shown in <FIG>). Communication interface <NUM> further includes a software or firmware interface for receiving one or more requests for reading, for example, measurement data from memory device <NUM>. In certain embodiments, communication interface <NUM> may include, for example, a software application programming interface (API) for writing program code to memory device <NUM> or reading measurement data from memory device <NUM>.

Health monitor circuit <NUM>, in certain embodiments, may also include a backup battery (not shown) that supplies power to the various components of health monitor circuit <NUM> when electric machine <NUM> is not being powered or when any one of energy storage device <NUM>, rectifier <NUM>, voltage regulator <NUM>, or current transformer <NUM> fail.

<FIG> is a flow diagram of an example method <NUM> of monitoring health of an electric machine, such as electric machine <NUM>, e.g., an electric motor, coupled to mechanical load <NUM>. In alternative embodiments, method <NUM> monitors the health of an electric generator. Method <NUM> includes supplying <NUM> stator current to stator winding <NUM> of electric machine <NUM>. The stator current conducted through stator winding <NUM> and, more specifically, electrical conductor <NUM> that feeds stator winding <NUM>, electromagnetically couples <NUM> current transformer <NUM> to stator winding <NUM> and, more specifically, electrical conductor <NUM> that feeds stator winding <NUM>. The stator current induces a current in secondary winding <NUM> of current transformer <NUM>. The induced current is used to charge <NUM> energy storage device <NUM>. The induced current, which is generally an AC signal, may be rectified to a DC signal that is supplied to energy storage device <NUM>. Energy storage device <NUM> then supplies a DC signal to voltage regulator <NUM>, which regulates a desired DC voltage that is supplied to the various components of health monitor circuit <NUM>, including, for example, microprocessor <NUM>, sensors <NUM>, communication interface <NUM>, and memory device <NUM>.

Microprocessor <NUM> periodically collects <NUM> a stator current measurement from current transformer <NUM> based on the current induced in secondary winding <NUM>. Microprocessor <NUM> also periodically collects measurements from sensors <NUM> and writes measurements from sensors <NUM> and current transformer <NUM> to memory device <NUM>. In certain embodiments, microprocessor <NUM> periodically collects <NUM> the stator current measurement by transmitting a control signal to a switch in current sense circuit <NUM>. The switch is commutated to close a current measurement circuit in current sense circuit, which may include, for example, a current sense resistor or other suitable current sensing device. Method <NUM> may further include detecting a voltage in the current measurement circuit that represents the current induced in secondary winding <NUM>. The detection may be carried out by an amplifier, such as a current sense amplifier, that then transmits an analog stator current measurement signal to microprocessor <NUM> that represents the current induced in the secondary winding and, further indicative of the stator current conducted through electrical conductor <NUM> and stator winding <NUM>.

In certain embodiments, microprocessor <NUM> periodically collects <NUM> the stator current measurement by generating the control signal to commutate the switch within current sense circuit <NUM> at a sampling frequency of at least the frequency of the stator current supplied to stator winding <NUM>.

The methods and systems described herein may be implemented using computer programming or engineering techniques including computer software, firmware, hardware or any combination or subset thereof, wherein the technical effect may include at least one of: (a) enabling stator current measurement on electric machines; (b) enabling retrofit of electric machines to add stator current measuring using a current transformer that may be "clamped" onto a stator winding or an electrical conductor that feeds the stator winding; (c) enabling measurement of additional operating parameters and environmental conditions including ambient temperature, acceleration, ambient humidity, and barometric pressure; (d) improving fidelity of data collection for improved health monitoring by increasing sampling frequency, adding measureable parameters, and combining measurement data with stator current measurements; (e) harvesting energy to power health monitor circuitry from the current transformer that enables stator current measurement; (f) enable periodic measurement of stator current by storing of energy harvested by the current transformer from the electromagnetic field generated by the stator current to further enable alternating periods of charging and measuring; and (g) enabling the electric machine to operate as a sensor for monitoring operating parameters or environmental conditions of the mechanical load to which the electric machine is coupled.

In the foregoing specification and the claims that follow, a number of terms are referenced that have the following meanings.

As used herein, an element or step recited in the singular and preceded with the word "a" or "an" should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to "example implementation" or "one implementation" of the present disclosure are not intended to be interpreted as excluding the existence of additional implementations that also incorporate the recited features.

Here, and throughout the specification and claims, range limitations may be combined or interchanged. Such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.

Some embodiments involve the use of one or more electronic processing or computing devices. As used herein, the terms "processor" and "computer" and related terms, e.g., "processing device," "computing device," and "controller" are not limited to just those integrated circuits referred to in the art as a computer, but broadly refers to a processor, a processing device, a controller, a general purpose central processing unit (CPU), a graphics processing unit (GPU), a microcontroller, a microcomputer, a programmable logic controller (PLC), a reduced instruction set computer (RISC) processor, a field programmable gate array (FPGA), a digital signal processing (DSP) device, an application specific integrated circuit (ASIC), and other programmable circuits or processing devices capable of executing the functions described herein, and these terms are used interchangeably herein. The above embodiments are examples only, and thus are not intended to limit in any way the definition or meaning of the terms processor, processing device, and related terms.

In the embodiments described herein, memory may include, but is not limited to, a non-transitory computer-readable medium, such as flash memory, a random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and non-volatile RAM (NVRAM). As used herein, the term "non-transitory computer-readable media" is intended to be representative of any tangible, computer-readable media, including, without limitation, non-transitory computer storage devices, including, without limitation, volatile and non-volatile media, and removable and non-removable media such as a firmware, physical and virtual storage, CD-ROMs, DVDs, and any other digital source such as a network or the Internet, as well as yet to be developed digital means, with the sole exception being a transitory, propagating signal. Alternatively, a floppy disk, a compact disc - read only memory (CD-ROM), a magnetooptical disk (MOD), a digital versatile disc (DVD), or any other computer-based device implemented in any method or technology for short-term and long-term storage of information, such as, computer-readable instructions, data structures, program modules and sub-modules, or other data may also be used. Therefore, the methods described herein may be encoded as executable instructions, e.g., "software" and "firmware," embodied in a non-transitory computer-readable medium. Further, as used herein, the terms "software" and "firmware" are interchangeable, and include any computer program stored in memory for execution by personal computers, workstations, clients and servers. Such instructions, when executed by a processor, cause the processor to perform at least a portion of the methods described herein.

Also, in the embodiments described herein, additional input channels may be, but are not limited to, computer peripherals associated with an operator interface such as a mouse and a keyboard. Alternatively, other computer peripherals may also be used that may include, for example, but not be limited to, a scanner. Furthermore, in the exemplary embodiment, additional output channels may include, but not be limited to, an operator interface monitor.

The systems and methods described herein are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein.

Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

Claim 1:
A health monitor circuit (<NUM>) for an electric machine (<NUM>), the health monitor circuit (<NUM>) comprising:
a plurality of sensors (<NUM>) including a current transformer (<NUM>) configured to be electromagnetically coupled to an electrical conductor (<NUM>) that feeds a stator winding (<NUM>) of the electric machine (<NUM>), wherein the current transformer (<NUM>) enables measurement of a stator current conducted through the stator winding (<NUM>);
a rectifier (<NUM>) coupled to the current transformer (<NUM>) and configured to convert an alternating current (AC) signal generated by the current transformer (<NUM>) to a direct current (DC) signal to supply power for the health monitor circuit (<NUM>);
a memory device (<NUM>); and
a microprocessor (<NUM>) coupled to the memory device (<NUM>) and the plurality of sensors (<NUM>), the microprocessor (<NUM>) configured to periodically collect a stator current measurement from the current transformer (<NUM>) and write the stator current measurement to the memory device (<NUM>) by controlling alternating between first periods of supplying power for the health monitor circuit (<NUM>) and second periods of receiving stator current measurements at a sampling frequency of at least a frequency of an AC signal conducted by the stator winding (<NUM>) to collect the stator current measurement at least once per cycle of the AC signal supplied to the stator winding (<NUM>) before switching to supplying power for the health monitor circuit (<NUM>).