Some customers, when visiting the factory, raise the question of whether the motor products can be repeatedly subjected to dielectric withstand voltage testing. This question has also been asked by many motor users.Dielectric withstand voltage testing is a detection test for the insulation performance of motor windings during the production processing, as well as for the whole machine product testing. The criterion for judging qualification is that the insulation is not broken down under specified conditions.
To ensure that the motor insulation performance meets the requirements, in addition to choosing suitable electromagnetic wire and insulating materials, reliable process guarantees are also necessary. For example, protection during the processing, suitable fixtures, good impregnation equipment, and appropriate process parameters.
Taking the windings of high-voltage motors as an example, most motor manufacturers will perform turn-to-turn and dielectric withstand voltage tests on each coil. Before impregnation, the core with windings and the whole machine during the inspection test will undergo dielectric withstand voltage testing. This brings us back to the customers' doubts about the dielectric withstand issue.
Objectively speaking, dielectric withstand voltage testing is an irreversible destructive test. Whether it is for windings or individual coils, it is not recommended to conduct repeated tests, with the necessity of finding problems as the premise. In special cases where repeated testing is required, the test voltage should be reduced according to the relevant standard requirements to minimize damage to the insulation as much as possible.
Regarding the Dielectric Withstand Voltage Tester
The dielectric withstand voltage tester is an instrument for measuring the dielectric withstand voltage strength. It can intuitively, accurately, quickly, and reliably test various electrical safety performance indicators such as the withstand voltage, breakdown voltage, and leakage current of the tested objects. Through the dielectric withstand voltage tester, problems can be found and the compliance of insulation performance can be determined.
● Detect the ability of insulation to withstand working voltage or overvoltage.
● Check the quality of insulation manufacturing or maintenance of electrical equipment.
● Eliminate damage to insulation caused by raw materials, processing, or transportation, and reduce the early failure rate of products.
● Inspect the compliance of electrical clearance and creepage distance of insulation.
Principles for Selecting Dielectric Withstand Voltage Test Voltage
The best way to determine the test voltage is to set it according to the specifications required for the test. Generally, the test voltage is set at 2 times the rated voltage plus 1000V. For example, if a product has a rated voltage of 380V, the test voltage would be 2 x 380 + 1000 = 1760V. Of course, the test voltage may also vary depending on the insulation class and different product types have different voltage requirements.
Why is it important to frequently check the integrity of the test circuit?
Dielectric withstand voltage testers on the production line are used very frequently, especially the test leads and test fixtures which are often in motion, making them prone to internal core wire breakage and open circuits, which are generally not easy to detect. If there is an open circuit at any point in the loop, the high voltage output by the dielectric withstand voltage tester cannot truly be applied to the tested object. These reasons can cause the set high voltage not to be truly applied to the tested object during dielectric withstand strength testing, and naturally, the current flowing through the tested object will be almost zero. Since it does not exceed the upper limit set by the dielectric withstand voltage tester, the instrument will give a prompt that the test is qualified, considering the insulation to be qualified. However, the test data in this case is not true. If the tested object happens to have insulation defects at this time, it will lead to serious misjudgment.
Post time: Jan-16-2025