Reactive power compensation capacitor contactor we generally call it capacitor contactor, its model is CJ 19 (some manufacturers model is CJ 16), common models are CJ 19-2511, CJ 19-3211, CJ 19-4311 and CJ 19-6521, CJ 19-9521.
To know the purpose of the three lines, we first need to understand the structure of the contactor.
In fact, it consists of three parts:
1. The contactor part is CJX 2 series AC contactor, such as CJ 19-3211 its contactor is CJX 2-2510 as the basic contactor.
2. The contact, or the white auxiliary contact above the contactor, consists of three electrified often-on contacts and a normally closed contact. Due to design factors, it contacts the contact before the main contact of the main contact.
3. The damping line, which is the three lines. Speaking of damping, it is actually a wire with a large resistivity, also known as the resistance line, equivalent to a high power resistance, its role is to inhibit the current effect.
We know that a capacitor is an energy storage element, its basic characteristics are: AC resistance DC, high frequency resistance low frequency, its current is the advance voltage 90 degrees and the physical characteristics of the inductor, so it is used to compensate for the reactive power load in the offset line.
Knowing the characteristics of the capacitor, then when the capacitor is electrified, because it is an energy storage element, when it is just electrified, it is bound to produce a large charging surge. Its current is generally dozens of times of the rated current of the capacitor, and then it will decay with the charging cycle until the normal working current.
This surge flow is very fatal to the service life of the capacitor, because the line load will change the reactive power of the line, which is necessary to regularly adjust the number of input and capacitor compensation groups to achieve the best compensation effect.
After using the capacitor contactor, when the auxiliary contact and damping line on the contactor are connected on the current, the damping line is used to suppress the inflow of the capacitor, so as to protect the capacitor and increase the service life of the capacitor.
This contactor for reactive power compensation cutting capacitor is basically the same as the geometry and appearance of common contactors, only three more pairs of auxiliary contacts. Why are there three auxiliary contacts? If you look closely, that’s not an auxiliary contact, there’s a resistance wire on it, right?
It is the current limiting resistance, in the moment of sending power to the capacitor, the capacitor will produce a large charging current, vividly called surge, describes the instantaneous current meaning. This current can be dozens of times the rated current of the capacitor, such a large instantaneous current causes damage to the contact, capacitor and other electrical components of the capacitor, and also has an impact on the system.
In order to limit the surge flow, the current limiting resistance is added, and the small current is pre-charged to the compensation capacitor when input. When the contactor coil is charged, the current-limiting resistance first connects the power supply and the capacitor to charge the capacitor. With this resistance, the surge can be limited to 350 times; then the main contact of the contactor is closed, for a smooth transition.
Compensation capacitors of different capacity, the specifications of the matching contactors are different, and are marked on the capacitor, can also be estimated.
Post time: Mar-07-2023
