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Small And Medium - Sized NEMA Standard Motor Repeat Shock Wave Test
Oct 31, 2017

Many manufacturing plants use repetitive shock wave testing as part of the NEMA standard motor components (eg stator and rotor) as a quality control test. When testing a large number of two NEMA standard motors with the same design, the repetitive shock wave test is quick and economical for detecting the following defects.

A. Winding grounding

b. turn short circuit

c. Winding short circuit

d. Wrong wiring

e. turns error

f. Conductor or Insulation Dislocation Repetitive Shock Wave Test is to compare an unknown winding with a known winding or an ideal good winding. That is, the shock wave waveforms on the two winding terminals are compared on the same oscilloscope. Larger defects are easy to detect, but require less skilled operator identification for smaller defects. For example, when the slot insulation is dislocated, or when two or more workers are produced, small defects are caused by the shaping of the winding coil or the winding end.

However, due to some of the shortcomings of the repetitive shock wave test, its general use has been limited, for example, before performing a shock wave test, a detailed test must be carried out. For example, there may be a resonance that would produce an abnormally high or low stress somewhere in the NEMA standard motor part insulation structure. Therefore, it is necessary to study the voltage distribution of the windings. When the number of these components is small, the detailed pre-test also shows how many problems. Design of the smaller changes, but also to conduct a detailed pre-test. When performing a repetitive shock wave test, the impulse voltage level and other test conditions shall be based on laboratory test data obtained on a specially designed (or several design) NEMA standard motor.

When a rotor or a stator has two or more identical windings, each winding, such as a multiphase stator, can be compared with another winding because the defects of any two identical windings are not necessarily the same. In order to make the shock wave test practicable, a similar design of the NEMA standard motor rotor or stator for each test, but from several different design pre-test to accumulate enough data is essential. When the rotor or stator does not have two identical windings, if the phase stator and the DC armature, there must be two identical parts for repetitive shock wave test. If the test is found to be unqualified, at least three parts are tested to determine Which one failed. It should be noted that, unless a large number of comparative breakdown tests have been carried out, there has been no satisfactory method to determine the equivalent value of the shock wave test voltage equivalent to the 60 Hz dielectric strength test.