SU843112A1 - Device for testing heating of induction motor - Google Patents

Description

(54) DEVICE FOR TESTING FOR HEATING ASYNCHRONOUS ENGINE

prototypes for which the heating test is one of the most important are usually made in the singular. In addition, at the indicated connection of the phases of the winding device and the flow of them by a constant current, a magnetizing force (B.C.), mobile in the resultant space, is produced, the magnitude of the main harmonic of which exceeds the nominal voltage. three-phase current is approximately .Q but 1.3 times. When the rotor rotates in a magnetic field due to the specified NS, it induces currents of frequency close to the nominal, and there are losses that are several times higher than the nominal (due to the effect of current displacement). Increased losses cause overheating of the rotor and distort test results.

The purpose of the invention is to eliminate these drawbacks, namely, to simplify and improve the accuracy of the heating test of induction motors.

In order to achieve this goal, a direct current source is included 25 between the neutral point outputs of the 66th current of the motor under test and the output unit of the alternating current source.

FIG. 3. shows a schematic diagram of the device for testing the AOR for heating three-phase asynchronous motors; an alternator was used as an AC source; 2 - the same, the test motor is connected to a 35 AC source through a three-phase transformer.

The device consists of a test three-phase asynchronous motor 1 phase 2-4, the stator windings of which are connected in a star, forming a neutral point 5. Phase 6-8 of the stator windings of the alternating current generator 9 (figure 1) are connected in a star, forming a neutral point 10 and phases 11-13 of the secondary winding of the transformer 45 (figure 2) are connected into a star, forming a neutral point 15.

Phases 2–4 of the stator windings of the motor under test 1 and phase 6–8 of the alternating current generator 9 are connected respectively to each other (FIG. 1), and between them the neutral point 16 of the direct current is switched on between their neutral points 5 and 10.

 2-4, the stator windings of the test motor 1 and the phases 11-13 of the secondary winding of the three-phase transformer 14 (FIG. 2) are also interconnected, and a DC source 16 is connected between their neutral points 5 and 15. The primary winding 0 17 of a three-phase transformer 14 is connected to an AC source 18, which can be served by an electric machine generator or a common network.65

The device works as follows.

When the engine 1 rotates at idle, the direct current from the generator 16 creates the necessary current load on the stator winding of the test motor 1, and the effective value of this phase is determined by the values of DC and AC.

At a nominal stator voltage and an effective value of the current in the phase equal to the nominal, nominal losses in the stator winding and core are ensured.

A constant current flows in all phases of the motor 1 in the same direction, for example, from the beginning of the phase to the end, (figures 1 and 2 are arrows).

Accordingly, the fundamental harmonic of the magnetic field produced by the resultant n. S. direct current, is obtained equal to zero. At the same time, in the air gap of the engine 1, a third harmonic of the magnetic field arises, stationary in space,. which creates additional rotor losses. The magnitude of the losses in the rotor during testing is equal to the difference between the measured values of the power supplied to the motor at a given value of direct current and at a constant current equal to zero.

If, at the rated current load of the winding and the nominal losses in the stator core, the rotor losses with the nominal losses are insignificant, then the measured temperature rises practically correspond to the nominal ones. In the general case, the difference between the actual nominal losses in the rotor AR causes a change in the temperature of the cooling air by

dR

Magnitude and in,

where P is the loss.

ftPr

corresponding to the excess temperature of the cooling air, which can be taken as an amendment to the measured values of exceeding the temperature of the winding and the stator core.

In the proposed device, the power of the power sources does not exceed 5-10% of the rated power of the tested engine, since the AC source covers only the no-load losses of the tested engine, the rotor losses and the total losses in the transformer, and the DC source is part of the main losses in the stator winding.

The proposed scheme is simpler than the known ones, for testing according to this scheme, neither the installation of the loading machine with the use of current transducers, nor the second motor, with the test subject, is required. This will also reduce the cost of equipment by eliminating the test benches needed to test the engines under the direct load scheme.

The additional effect of the present invention is determined by the decrease in the accuracy of the test results, making it possible to improve the technical and economic indicators of newly developed engines based on more reliable experimental data.

Claims (2)

Invention Formula A device for testing the heating of a three-phase winding asynchronous motor, equipped with a neutral point output, containing an alternating current source, the output unit of which is designed as a three-phase winding — with a neutral point output and an adjustable direct current source, as in In order to simplify the device and improve the accuracy of the test, the DC power source is included between the terminals of the neutral points of the windings: the motor under test and the output block of the AC source. Sources of information accepted by you during the examination of j 1. Gerva GK Industrial testing of electrical machines. Energy 1968. , 2. OST 16 0.688.040g73. Electric machines. Experienced load methods for testing. General 0 1 guidelines. (Put. 2