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Liaoning Jinli Electric Power Electrical Appliance Co.,Ltd

Notes on selection of tap changer for converter transformer

According to the working characteristics, the use of on-load tap changer should follow the following principles, adjust the selected tap-changer rated value.

(1)Selection of maximum rated pass current for Tap changer

Considering that the current of the converter transformer contains higher harmonics and overload current, the overload capacity of the load current of the tap changer can be increased, and the tap switch should be used within the reduced tolerance limit of 70%. Therefore, the use of tap-changer maximum rated through current should be considered to leave a certain margin.

(2)Voltage and level capacity of tap-changer

Considering that the recovery voltage at the fracture of the tap-changer has high harmonics, it will affect the ignition of the arc. Therefore, the tap switch-level voltage in principle to the maximum level of allowable voltage demotion (90%) and allowable limit breaking capacity (defined as 1.1PN = 1.1usmax·In, the type test according to increase 10% grade voltage to examine and use. and the transition resistance should be carefully considered that the recovery voltage on the contact head is limited to the allowable contact opening strength range.

(3) Life Index

Mechanical life 800,000 times, contact electrical life: The transformer load current reached the TAP switch maximum rated through the current is greater than 200,000 times, according to the reduction capacity 70% selected tap switch contact electrical life more than 300,000 times.

(4) Overhaul Oil Change cycle

The tap changer is provided with an on-line net oil installation auxiliary equipment, and the overhaul oil change cycle is more than 100,000 times.

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