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Liaoning Jinli Electric Power Electrical Appliance Co.,Ltd

Technical Requirements For Non-excitation Tap-changer

No excitation tap changer shall meet the following technical requirements according to the voltage level and the use range.

1. Contact pressure

When the contact pressure between the movable contact and the fixed contact is increased, the contact resistance decreases. But the pressure is too much, will not make the contact resistance continue to reduce, and make the torque increase accordingly. Contact pressure is generally required to be 25〜50n, measured using a dedicated manometer or spring. The minimum contact pressure of the measured contact is the separation force when the signal in series of the contact is extinguished or the thickness of the movable contact is less than 0.1mm.

2. Contact resistance

Contact mode is theoretically divided into point contact, line contact and contact with three kinds of contacts, in fact, there are only a few contacts between the stationary contact. Contact resistance and contact pressure, contact material. Contact surface roughness and technical contact area, generally should be less than 500μΩ, electric bridge method or voltage drop method to measure, if the voltage drop method to measure the current should be less than the rated passing current of 1/3. The 1~3 operation cycle of the tap changer should be carried out before the child is measured.

3. Insulation withstand pressure

The phase voltage of the full wave of the no excitation tap changer and the voltage in the middle or end is equal to 100% of the voltage of the lightning impulse test of the transformer, the voltage gradient between the contacts is about 3 times times of the adjustable pressure percentage (refers to the gradient within the pressure range). The power frequency to ground voltage and the interphase electric s are both Transformer's work frequency withstand voltage value. No excitation tap changer in the insulation withstand pressure test, the switch must be dry, and then immersed in the pressure of MKV to H of the transformer oil, so that all escape the bubble, impregnation time requirements not less than 0.5h. When the tap-changer adopts the plastic pressing piece, it must be tested in the transformer oil of the 85~100℃; other tap-changers can be carried out in the air, but the pressure resistance decreases by 2.5 times times and lasts for 5min.


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