Patent Application
20210296968
The present invention relates to measuring the temperature in an electric motor.
More specifically, the present invention relates to a system and method for measuring the temperature of a tightly wound stator field winding in an electric motor.
A common hindrance to motor performance is overheating. Excessive temperatures can build up in the windings of a motor, and interfere with motor function. In some cases, this can result in motor damage and even cause the motor to catch fire. Accordingly, many motors use thermal devices as a means of detecting and/or preventing excessive temperatures.
Thermal devices are generally placed inside the windings of the motor and bonded thereto by an adhesive, varnish, or encapsulation. This method is successful when the windings are loose, but has been proven difficult to execute when the windings are tightly wound, given that the thermal devices must be bonded or pressed against the windings. Accordingly, there is a need in the art for a method and system for effectively measuring motor temperature in a tightly wound stator field winding.
An objective of the invention is to simplify the process for attaching an insulated, thermo-electric temperature device in an electric motor for the purposes of measuring the temperature of a field winding.
In accordance with a preferred embodiment of the invention, the system of the present invention includes an electric motor having a stator and field windings thereon. The system further includes, a thermo-electric temperature device for measuring temperature mounted on the surface of a circuit board adjacent to the motor stator. The device is preferably one that is capable of measuring the temperature of the field windings in the electric motor. It may be appreciated that upon receiving a reading of excessive temperatures from the field windings, the motor electronics may alter the flow of current to the field windings, thereby preventing the motor from overheating.
The system further includes a thermally conductive material disposed onto at least one of the field windings of the stator. The thermally conductive material is preferably comprised of a material that is thermally conductive, but not electrically conductive. The circuit board is preferably arranged proximally to the thermally conductive material such that the device is in contact with the thermally conductive material. It will be appreciated that the thermally conductive material conducts the heat from the field windings to the device such that the thermal sensor reads the approximate temperature of the field windings. Furthermore, the thermally conductive material creates an intimate contact between the device and the windings. The intimate contact between the device and the windings is preferred as it ensures that the device, which is secured to the circuit board, relays accurate temperature readings of the windings without the needing to be in direct contact with the winding.
The features and advantages of the invention are apparent from the following description taken in conjunction with the accompanying drawings in which:
The invention relates to a system for measuring the temperature of field windings in an electric motor.
The system further includes a circuit board 104 having a thermo-electric temperature device 106 mounted thereon. The temperature device 106 may be of a material capable of conducting heat, and preferably having a resistance of 100-1000Ω at 0° C. Possible thermo-electric temperature devices for use in the invention include, but are not limited to, switching devices including bimetallic relays, avalanche PTC thermal sensors, resistive thermal devices (RTD) including KTY or PT1000. An exemplary thermo-electric temperature device of the type used in the invention is an Adafruit Platinum RTD PT1000 Sensor, Product ID: 3984, having a platinum resistance thermometer and a resistance of 1000Ω. The circuit board 104 is positioned adjacent to the field windings 102 with the surface of circuit board 104 on which the temperature device 106 is mounted facing field windings 102. Temperature device 106, mounted on the surface of the circuit board 104, is in direct contact with and surrounded by a thermally conductive material 108, positioned between the temperature device 106 and the field windings 102.
The thermally conductive material 108 is a compound suitable for conducting heat, but is preferably not electrically conductive. Examples of thermally conductive material of the kind used in the invention, include, but are not limited to adhesives, epoxies, greases, and pastes, as well as thermal pads, sheets, or foams. An example of a preferred thermally conductive material includes a thermal compound having a thermal conductivity greater than 2.5 W/(m-K), such as a Parker Therm-a-form CIP35 Thermally Conductive Cure-In-Place Compound. The thermally conductive material 108 operably connects the temperature device 106 to the field windings 102, and is configured to conduct heat from the field windings 102 and transmit such heat to the temperature device 106 with which the thermally conductive material 108 is in contact. In one embodiment, the thermally conductive material 108 may act as a binding agent, thereby binding the temperature device 106 to the field windings 102. In another embodiment, the thermally conductive material 108 may be compressed between the temperature device 106 and the field windings 102. The intimate contact of the temperature device 106 to the thermally conductive material 108 ensures that the temperature device 106 maintains proper heat conduction while the electric motor is running, ensuring consistent and accurate temperature readings of the field windings 102. Upon detecting an exceedingly high temperature reading from the temperature device 106, the motor electronics may alter or stop the flow of current to the field windings 102, thereby preventing the electric motor from overheating.
As is known in the art, the electric motor may include a circuit board 104.
The graph in
Although this invention has been shown and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions, and additions in the form and detail thereof may be made therein without departing form the spirit and scope of the invention. Accordingly, the present invention has been shown and described by way of illustration rather than limitation.
