Three-phase circuit tester

Abstract

The invention discloses a three-phase circuit tester. The tester comprises a sinusoidal oscillator, a voltmeter, an ammeter and a three-phase load, wherein the signal output terminal of the tester is connected with a non-shift-phase power amplifier and a two-circuit shift-phase power amplifier separately, and a work power supply provides a stabilized voltage direct current power supply for the above circuits. The stable low voltage three-phase alternating current with the equal three-phase voltage and 120 degrees of phase difference of three-phase voltage can be outputted, wherein the common ground wire is the neutral line of the three-phase alternating power supply. The detects of the existing three-phase alternating current experimental instrument, like unbalanced three-phase voltage and phase difference, instability, unsafety, large power consumption and volume and the like can be well solved. The tester can be used to conveniently observe the neutral current generation phenomenon caused by the unbalanced three-phase voltage or phase difference. The tester can be single used as the experimental instrument and can be combined with the common electrotechnics and electronic engineering practice rig. The tester can be used in the three-phase alternating current experimental project of various colleges and universities, thus greatly improving the experimental accuracy and effect and avoiding the risk of electric shock in experiments.

Description

Technical field [0001] The invention relates to an experimental device, in particular to a three-phase circuit experimental instrument. Background technique [0002] In domestic universities of all levels and types, the three-phase AC experiment is one of the electrical and electronic experimental projects that science and engineering students must do. The existing experimental devices used for this experiment are nothing more than two categories: one is a completely separate The instrument is assembled by the students to assemble the experimental circuit. The other type is to install the relevant instruments and equipment on the electrical and electronic experiment table. The students only need to plug in and connect according to the circuit. For example, the experimental project of "Measurement of Voltage and Current in Three-phase Circuits" (pages 70-72) in the university experimental textbook "Electrical Engineering and Electronics Practice Course" compiled by Fu Jiacai publi...

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Problems solved by technology

However, the three-phase AC power used in the above two types of experimental methods is directly taken from the three-phase AC mains, and for the three-phase AC mains, due to the uncertainty of the three-phase load of the entire grid system (the three-phase load is in each The time is random, resulting in unbalanced three-phase load) and the internal resistance of the power supply system is not zero, resulting in unbalanced and unstable three-phase electricity, which is manifested in the unequal and unstable three-phase voltages, and the phase difference of the three-phase voltages Also not 120 degrees or unstable

These will cause great errors in the experimental results, and even make it difficult for teachers and students to tolerate.

Not only that, the voltage of the three-phase AC mains is very high, and the safety of experimental instruments and people is low. Accidents such as equipment burnout often occur, and electric shocks sometimes occur (although usually due to good insulation, serious electric shock accidents are not prone to occur, but every This experiment still worries the teachers and students), and consumes a lot of power. The total power consumption of the light bulbs of each set of experimental instruments reaches one or two hundred watts, and the experimental equipment is bulky and heavy.

In addition, it is not possible to demonstrate the change of the neutral line current when the three-phase AC power supply changes from a balanced state to an unbalanced state.

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