Winding temperature rise is an important performance indicator of a motor . There are two ways to calculate motor temperature rise: one is to use the resistance method, which calculates the temperature rise of the winding based on the change of the DC resistance of the winding; the other is to use a temperature measuring element for detection.
The resistance method is suitable for motor type testing, and can calculate the temperature rise of the motor relatively objectively and accurately. However, the hot resistance test is carried out when the motor is stopped, and the final test result deviates slightly from the actual value. However, the resistance method can reflect the overall temperature rise of the winding relatively accurately, and is therefore more accurate.
The use of temperature sensing elements is primarily for monitoring motors after they are put into use. One method is to detect the temperature rise of the windings, and the other is to monitor the bearing temperature. This method provides dynamic monitoring and measurement of the motor during operation, resulting in more timely data. It can also be linked to a control device according to pre-set parameters for temperature protection of the motor windings. However, the placement of the temperature sensing element is directly related to the final displayed temperature, meaning that the results obtained using temperature sensing elements are subject to uncertainty.
1. Resistance method for measuring temperature rise
The resistance method measures the temperature of a coil by observing the change in its resistance when it heats up. Specifically, it uses the relationship between the coil's DC resistance and its increasing resistance with rising temperature to determine the average coil temperature. Within a certain temperature range, the resistance of the motor coil will increase accordingly with rising temperature, and there is a specific functional relationship between its resistance and temperature.
2. Temperature sensing element
A temperature sensing element is the detection element of a temperature measuring instrument. Examples include thermocouples, resistance temperature detectors (RTDs), and thermistors. The temperature measured by a contact-type temperature measuring instrument is determined by the temperature sensed by the sensing element. After selecting an economical and reasonable temperature sensing element and secondary instrument that meets the accuracy requirements of production, the correct installation of the sensing element becomes a crucial practical issue. Improper instrument installation will lead to distorted measurement data.
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