Method for checking welding quality of stator winding joint of large power generator

Abstract

The invention discloses a method for checking the welding quality of a stator winding joint of a large power generator, comprising the following steps: 1) outputting constant 50A direct current by virtue of a 50A transformer direct-current resistance tester so as to be connected with the two ends of the stator winding joint; 2) utilizing a 0.2A-level current divider for measuring current and a direct-current voltmeter to monitor a direct-current value; and 3) measuring the voltages at the two ends of a joint resistor by using a high-accuracy digital multimeter, and converting the voltages into a resistance value. By utilizing the method, the measuring accuracy of the resistance value of the stator winding joint can reach 0.2mu Omega. According to the method disclosed by the invention, the voltages of the two ends of the joint resistor are measured by the high-accuracy digital multimeter so as to improve the accuracy, so that not only can large current be guaranteed, but also the high accuracy is met. The invention provides a method for measuring a resistance value of the welding joint simply, conveniently and accurately, so that the accuracy of the welding joint of a measured winding can be guaranteed, and an accurate resistance value is provided for the welding quality of a bar joint so as to handle the unqualified welding joint in time.

Description

technical field [0001] The invention relates to the field of maintenance of large-scale generators in water conservancy projects, in particular to a method for checking the welding quality of stator winding joints of large-scale generators. Background technique [0002] The stator winding of the generator is composed of many wire rods welded in series. These welding joints will be affected by various mechanical vibrations during the operation of the generator, and will be affected by the short-circuit current and the electromotive force generated by the short-circuit current when a fault occurs. In order to ensure that the temperature of each joint of the generator stator winding is in the normal range during the operation of the unit and prevent the occurrence of open welding accidents, the quality control of the welding of the stator winding joints during the installation process is particularly important. [0003] The existing methods for checking the welding quality of t...

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Problems solved by technology

However, under field conditions, when measuring with a loop resistance tester, the volume of the current test clamp of the tester is too large, and the space of the wire rod is small, and forced wiring may damage the insulation layer of the wire rod. The current test of the loop resistance tester The pliers cannot be connected to the narrow gap of the stator bar. The measurement range of the general loop resistance tester is also greater than 1μΩ (the resistance value of the joint with good welding quality is between 0.2μΩ-0.8μΩ), and it is measured with a 50A transformer DC resistance tester. Although it can meet the requirements of high current required for measuring small resistance values, and the clamps are easy to penetrate into the gaps of wire rods for wiring, the resistance value of the welded joints exceeds the accurate measurement range of the transformer DC resistance tester (the transformer DC resistance tester's Measurement accuracy is between 50μΩ—0.4Ω)

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