By hvhipot 
Motor AC voltage withstand test? HV Hipot Electric Co., Ltd. specializes in producing AC withstand voltage testers with a wide range of product options. When looking for an AC voltage withstand tester, choose HV Hipot Electric Co., Ltd..
1. Purpose of AC withstand voltage test
AC withstand voltage test is the most effective and direct method to evaluate the insulation strength of power equipment. During operation, the insulation of power equipment will gradually deteriorate under the long-term effects of electric field, temperature, and mechanical vibration, including overall deterioration and partial deterioration, forming defects.
Although the AC withstand voltage test has an accumulation effect, it is closer to the actual operating state of the equipment and can expose some insulation defects of the equipment in advance, effectively discovering insulation weaknesses. Therefore, it is a firm test that determines whether the equipment can be put into operation.
Various preventive testing methods have their own strengths and can detect some defects and reflect the insulation condition. However, the test voltage of other testing methods is often lower than the working voltage of power equipment, but the AC withstand voltage test is generally higher than the operating voltage. Therefore, testing has become an important means to ensure the safe operation of transformers. The AC withstand voltage test is a relatively effective and direct method for evaluating the insulation strength of electrical equipment. It has a decisive significance in determining whether the electrical equipment can continue to operate, and is also an important means to ensure the safe operation of the equipment and avoid insulation accidents. Due to the fact that AC withstand voltage is a destructive test item, it must be strictly carried out in accordance with the standard regulations.
2. Voltage value for AC withstand voltage test
The most crucial issue in the AC withstand voltage test is to correctly select the value of the test voltage. On the one hand, it is required to maintain insulation level, and on the other hand, insulation degradation caused by high test voltage should be considered. Generally speaking, the following factors should be considered.
(1) The value, duration, and frequency of overvoltage that may occur on the test sample. If the possibility of the test sample being subjected to high overvoltage is extremely low, it is not necessary to use excessively high test voltage; If the test sample may be subjected to high voltage, the value of the test voltage should be appropriately increased.
(2) The insulation level used in the design of motors or electrical appliances.
(3) The condition of equipment insulation. Due to various conditions during operation, the insulation of the motor gradually deteriorates and the insulation performance decreases. Therefore, when determining the test voltage, the degree of insulation damage and operating life should be considered. For example, the test voltage of the running equipment should be 75-90% of the original factory voltage
(4) Spare parts, spare parts, and maintenance reseries resonances.
(5) The importance of motors and electrical appliances in the power system.
3. Factors affecting insulation AC voltage breakdown
(1) Temperature has a significant impact on insulation breakdown. As the temperature increases, the dielectric loss also increases. Poor heat dissipation conditions can lead to thermal breakdown, where an increase in temperature can cause a decrease in breakdown voltage.
(2) The power frequency is closely related to the dielectric loss. As the dielectric loss increases with the increase of power frequency, the breakdown voltage is also directly related to the power frequency.
(3) The pressurization time and voltage application time have a direct effect on the breakdown of insulation. If the applied voltage is high, the time required for breakdown to occur is shorter. If the applied voltage is low, the time required for breakdown to occur is longer.
(4) The degree of moisture absorption will cause a decrease in insulation breakdown strength when the insulation becomes damp. Materials that are not easily hygroscopic have a breakdown voltage that drops to about half of what it would be if they were not exposed to moisture. Materials that are easily hygroscopic may have a withstand voltage that is only one percent of what it would be when dry.
According to national standards, if the insulation structure of high-voltage electrical appliances, current transformers, bushings, and insulators is mainly composed of ceramic and liquid materials, only a 1-minute withstand voltage test is required; If it is mainly composed of organic solid materials, a 5-minute pressure test is required. For motors, the standard is a 1-minute withstand voltage time.