In the micro-motor production process, it is necessary to measure the various parameters of the motor. In the traditional micro-motor test, the dynamometer is generally used for loading. The torque tachometer displays the motor torque, the rotational speed and the output power, and the electrical parameter measuring instrument measures the input voltage and current of the motor. Test a number of working points of the motor, draw the corresponding coordinates on the coordinate paper, draw points, and connect into a curve. In this test method, since the reading time of each parameter is not synchronized, the relative relationship between the parameters does not correspond, manual operation and recording of test data are required, and the unstable region of the asynchronous motor cannot be tested. The computer-controlled motor automatic test system can solve these problems well. Its modular structure, intelligent instrument, freely combinable and automatic identification of the micro-motor automatic test system can not only automatically test and store data of various motors. , draw curves, and can post-process data.
The system consists of a machine, a hysteresis dynamometer, an electrical parameter measuring instrument, a programmable controller, a torque tachometer, and a printer. According to the motor test requirements, the above instruments and equipment can be flexibly composed of a variety of dynamometer systems. The system uses the P machine as the upper computer, and the single chip microcomputer is the lower computer of each measurement item. It combines the advantages of P-machine computing power and anti-interference of single-chip microcomputer to make the system reliable and stable. The P machine finishes issuing control commands and data processing, printing and drawing characteristic curves. The MCU completes the test, control, display, and transmits data to the host computer (P machine). The hysteresis dynamometer loads and detects the torque speed signal. The electric parameter measuring instrument is an AC-DC universal meter. The frequency range is to measure the input electrical parameters of the tested motor, such as voltage, current, power, etc. The power supply is connected to the input of the power meter, and the output of the power meter is connected to the motor under test. The programmable controller is introduced into the motor automatic test system. According to the instructions of the computer, the motor under test is loaded, and the torque and speed signals output by the dynamometer are amplified and stored in the memory unit for computer call and display. Through the programmable controller, the closed-loop control of the system is realized. The torque tachometer mainly receives the torque and speed signals from the dynamometer, and the torque and power are displayed after being processed by the programmable controller. The system block diagram is shown in Figure 1.
Load principle and torque and speed signal generation 3.1 Loading principle In the motor automatic test system, the hysteresis dynamometer is used. The brake principle diagram is shown in Figure 2. The brake is composed of the inner and outer stators and rotors. The excitation coil has a hollow cup shape and is made of a hysteresis material. Both the inner and outer stators have teeth and slots, and the inner and outer stators are mounted in a tooth-to-groove position. When a current is applied to the excitation coil, a magnetic field is generated in the air gap, and the magnetic field interacts with the rotor material to generate a torque proportional to the excitation current micromotor 2000, Vol. 33, No. 6 (total phase).
The torque signal generated by the torque signal is picked up by four strain-type torque sensors mounted on the brake cantilever beam. Two resistance strain gauges are respectively attached to both sides of the cantilever beam to form a full-bridge circuit, which is proportional to the torque. Analog voltage signal.
The generation of the rotational speed signal is coaxially mounted with an optical encoder. A photocell and a bulb are mounted at both ends of the optical encoder. The optical encoder is evenly distributed with teeth and slots. The optical encoder rotates for 1 week. The photocell generates 60 pulses, that is, a square wave whose photoelectric tube output frequency is proportional to the rotational speed.
The realization principle of the automatic test of the unstable region of the asynchronous motor When the T n curve of the asynchronous motor is tested by the traditional dynamometer, the constant torque power machine is generally used. When the load torque is greater than the maximum torque of the motor, the motor transitions from the maximum torque. In the locked state, it is difficult to operate stably at its working point, and the test of the operating characteristics of the unstable zone cannot be achieved. The motor automatic test system adopts a programmable controller, which can control the excitation current of the stator coil of the hysteresis brake according to the speed feedback signal, thereby achieving the purpose of controlling the torque. When a certain unstable zone speed value is set, the load torque increases. When the load torque is greater than the maximum torque, the motor transitions from a steady state to a stalled state, and the motor speed decreases. After the speed feedback circuit detects this signal, The programming controller reduces the excitation current, and at this time, the load torque is reduced, so that the motor can stably operate at a certain speed given in the unstable region, and the automatic test of the unstable region of the asynchronous motor is realized. In this way, the loading of the system is a closed loop control mode.
The main functions of the system The system has a good man-machine interface and operational performance. It can generate coordinates from the motor automatic test system Li Shuyang Lee fluctuation, and the X-axis and Y-axis coordinates can choose any parameter. Different test methods should be selected according to different motors during testing.
The main measurement functions of the system are: automatic measurement - high speed to low speed, automatic measurement - low to high speed, load curve, constant speed measurement, constant torque measurement, manual operation. Automatic measurement - the speed from high to low is suitable for measuring from no load until the selected minimum speed. Automatic measurement - the speed is measured from the lowest speed from low to high. The load curve function requires that multiple torque points be input once. After all points are input, the computer starts point-by-point testing. Constant speed measurement allows the user to keep the motor under test at the desired speed. Other functions include: printing, display data, print curve, screen display curve, and storage data. Figure 3 shows the T n curve measured by a 750W three-phase asynchronous motor using this system.
Conclusion With the rapid development of computer technology, the micro-motor automatic test system based on computer control will replace the traditional manual test. The micro-motor automatic test system with modular structure, intelligent instrument and free combination is the hope and eagerness of micro-motor manufacturers and test units, and it is also the development trend of future test instruments. The automatic test of the motor by the system can improve the test efficiency and measurement accuracy, and has good economic and social benefits.
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