Efficiency is an important indicator of motor performance. Especially driven by energy conservation and emission reduction policies, motor users are paying increasing attention to their efficiency. To accurately assess motor efficiency, standardized type testing must be performed and appropriate efficiency testing methods must be used. Taking a three-phase asynchronous motor as an example, there are three main methods for determining efficiency. The first is the direct measurement method, which is simple and intuitive and has relatively high accuracy, but it is not conducive to in-depth analysis of motor performance for targeted improvements. The second is the indirect measurement method, also known as the loss analysis method. Although the test items are many and time-consuming, the calculation amount is large, and the overall accuracy is slightly inferior to the direct measurement method, it can reveal the key factors that affect the motor efficiency and help analyze the motor. issues in design, process and manufacturing to optimize motor performance. The last is the theoretical calculation method, which is suitable for situations where test equipment is insufficient, but the accuracy is relatively low.
Method A, the direct test method of efficiency, is also called the input-output method because it directly measures two key data required to calculate efficiency: input power and output power. During the test, the motor needs to run under a specified load until the temperature rise stabilizes or for a specific time, and the load must be adjusted within a range of 1.5 to 0.25 times the rated power to obtain the operating characteristic curve. Each curve needs to measure at least six points, including three-phase line voltage, current, input power, speed, output torque and other data. After the test, the DC resistance of the stator winding needs to be measured and the ambient temperature recorded. When conditions permit, it is preferable to use live measurement or embed temperature sensors in the winding in advance to obtain the winding temperature or resistance.
Writer:Ziana
Post time: Apr-11-2024