Vacuum contactors are generally used in conjunction with current-limiting fuses. Vacuum contactors are used for on-off operation to make electrical equipment run or stop. Fuses are used for short-circuit protection, which can break the short circuit and cut off the faulty electrical equipment through melt melting. Only the tacit cooperation between contactor and fuse and the vacuum tester can control and protect the electrical equipment.
Contactors are vacuum type and SF6 type, and vacuum type is mainly used at present. According to its working principle, vacuum contactors have mechanical holding type, electrical holding type and permanent magnet holding type.
Mechanical holding type means that after the closing coil is electrified, the closing electromagnet is driven to drive the insulating rocker to close the main contact of the contactor, and after the closing is completed, the contactor is kept in the closed state by the closing locking device; Compressing the opening spring during the action of closing electromagnet; When the brake is opened, the trip coil is electrified, the opening electromagnet is driven to trip the closing lock, and the opening spring drives the operating mechanism to realize the opening.
Electrical hold type means that when closing, the closing relay and the closing latching relay switch instantaneously during the closing process, and when the closing relay loses power, it switches instantaneously to the charging of the closing latching relay, so that the closing coil is always charged; After the closing coil is electrified, the closing electromagnet is driven to drive the insulating rocker to close the main contact of the contactor and keep it in the closed state; Compressing the opening spring during the action of closing electromagnet; When the brake is opened, the power supply of the closing latching relay is cut off, and the closing coil loses power. Under the action of the opening spring, the contactors are quickly separated.
Permanent magnet holding type means that when closing, the closing coil is excited to produce electromagnetic force in the same direction as the permanent magnet, which acts on the armature to drive the crank arm to close the contactor main contact; After the closing is completed, the closing coil is powered off, and the permanent magnet force acts on the armature alone to keep the contactor in the closing position; When opening the brake, the opening coil is excited, which produces electromagnetic force in the opposite direction to the permanent magnet force, which weakens the effect of the permanent magnet on the armature and works together with the opening spring to realize opening the brake.
High-voltage vacuum contactor has a series of advantages, such as long life, small size, low price, frequent operation, less maintenance workload and good breaking performance, so it has been widely used.
The current-limiting fuse relies on quartz sand filled around the melt to absorb the heat of the arc and the diffusion of free gas to the quartz sand gap to extinguish the arc. Current-limiting fuse uses DC arc extinguishing method to break the current, that is, in the process of strong cooling, the arc voltage higher than the working voltage is established, so it has the function of current limiting. The advantage of this kind of current-limiting fuse is that it will be cut off at the initial rising stage of the current before the large expected short-circuit current appears, and the peak value of the expected current has not yet reached. In this way, the following electrical equipment will be protected from the impact of high electric load and thermal load, and it can not be designed according to the full short-circuit current before fusing, which will bring huge economic benefits. It should be noted that the protection characteristics of high-voltage current-limiting fuses must be correctly and reasonably selected, otherwise the expected protection effect will not be achieved.
Usage of vacuum tester
(1) This instrument can be used for two purposes:
1. It is used for the quality control of vacuum interrupters in the production line and the warehousing inspection of interrupters of circuit breaker manufacturers.
2. Used to detect the vacuum degree of the vacuum interrupter installed on the switchgear. This kind of detection mainly uses
Judging the bearing capacity of vacuum interrupter in routine maintenance and capacity test of power supply department.
(2) Connection:
Connect the output end of the magnetron current on the panel with the magnetron coil through wires, so that the contact of the interrupter is in a state of separation (the coil is sheathed outside the interrupter), and connect the high-voltage line and the signal input line to the moving end and the static end of the interrupter respectively. Note that the high-voltage line should be suspended (as shown).
note:
The instrument must be well grounded before use! There should be enough distance between the coil and the high voltage output end.
Check that the connection is correct before starting the machine.
After turning on the power of the instrument, the display screen displays the following menu:
(3) pipe type selection:
When measuring, first choose the tube type. There are many types of tubes stored in the instrument. See the appendix table for specific parameters.
1. Operation mode of pipe type selection:
Press [Select key] to make [◢ ◢] point to select the test pipe type, press [Confirm key], and use [+key] or [-key] to adjust the pipe type parameters. When the display shows that the pipe type is consistent with the pipe type code to be measured, press [Confirm key] to return to the main menu. If the pipe type to be measured is not given in the specification, it can be replaced by a pipe type with similar size and the same wiring mode.
2. Measurement
Press [select key] to make [◢ ◢] to test the vacuum tube "Pa", and press [confirm key] to make the instrument in the measuring state. And automatically complete all the measurement, calculation, display and other whole processes.
3. Print:
If you need to print test data, press [Enter] to return to the main menu, press [Select] to make [◢ ◢] print test data, and then press [Print] to print out all measurement data.
4. If there are no substitutable parameters, press the [select key] to make [◢ ◢] point to "A", so that the ionization current can be directly given. Generally speaking, Ionization current (A) is two orders of magnitude smaller than vacuum degree (Pa).
This instrument adopts the method of starting the high voltage twice. If the instrument returns to the initial state after starting the high voltage for the first time, it is rejected for inspection. Check whether the vacuum tube is in a closed state, if not, the tube has been seriously leaked or completely leaked.
Hainan electric network