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How to Adjust the Mechanical Characteristics of Vacuum Circuit Breakers?

This is about the method of adjusting the mechanical characteristics of vacuum circuit breakers, the content of adjusting the mechanical characteristics of vacuum circuit breakers. It is relevant to the adjustment of the total travel and contact distance, contact travel, opening and closing speed and three-phase synchronicity as well as the inspection of contact wear, etc.


1. Adjusting the total run of vacuum circuit breakers and contact opening distance


(1) The total stroke of the conductive rod is generally achieved by adjusting the height of the opening limit screw.


(2) The contact opening distance can be measured from the actual run of the dynamic conductive rod in the arc extinguishing chamber, or from the total run minus the contact travel.


When the contact distance does not meet the requirements, we can adjust the contact stroke of vacuum circuit breakers or the thickness of cushion cushion. If the cushion becomes thicker, the contact opening distance will be reduced. Otherwise its open distance is increased.


For a certain type of VCB circuit breaker contact opening distance, there are specific technical conditions. The choice range of vacuum circuit breaker contact opening distance under different rated voltage is as followed:  3 ~ 6 kilovolt (kV) for opening distance from 8 to 10 millimeters; 10kV for the opening distance from 10 to 15mm; 20kV for the opening distance from 15 to 20mm; 35kV for the opening distance from 20 to 35mm.


2. Adjustment of the contact stroke of vacuum circuit breakers


The contact stroke is usually about 15 ~ 40% of the opening distance of the contact. Contact distance plus contact stroke is the total stroke of the operating mechanism. The contact stroke is generally achieved by adjusting the thread between the connecting head of the insulation tie rod and the dynamic conductive rod of the arc extinguishing chamber. During the adjustment, we need to operate the VCB breaker with a special wrench, pull out the metal shaft on the insulator end, and adjust it by rotating the connection head of the conducting rod of the arc extinguishing chamber.


(1) The connector with a pitch of 1.5mm can be adjusted to 0.375mm, 0.75mm, 1.125mm and 1.5mm respectively when the angle of rotation is 90°, 180°, 270° and 360°.


(2) The connector with pitch of 1mm, the adjustment distance is respectively 0.25mm, 0.5mm, 0.75mm and 1mm respectively when the angle of rotation is 90°, 180°, 270° and 360°.


(3) If the connector can not be rotated by 90° and 270°, it can be achieved by rotating the Angle of the arc extinguishing chamber.


3. Adjustment of opening and closing speed of vacuum circuit breakers


The opening and closing speed of vacuum circuit breaker is adjusted by opening spring. If the opening spring force is large and the opening speed is fast, the closing speed will be slower accordingly. If the opening spring force is small and the opening speed slows down, the closing be accelerated .


4. Three-phase adjustment of vacuum circuit breakers


The maximum synchronous error of the vacuum circuit breaker in three-phase splitting and closing should not exceed 1 millimeter. The adjustment method is the same as contact stroking, and it is checked by three-phase synchronous indicator.


5. The inspection of contact wear degree of vacuum circuit breakers


The change in contact stroke is the wear of the extinguished contact. Therefore, after each contact stroke adjustment, the adjustment amount must be recorded. When adjustment accumulates to the contact wear thickness, the arc extinguishing chamber should be replaced.


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