Isolator, knife switch selection
Isolator, knife switch is the main function of isolated power supply. To satisfy the isolation of functional requirements of the premise, main principle is to ensure its rated voltage and rated voltage not to be lower than the corresponding data line, rated working current of not less than the calculated current line. When the required switching ability, must be with the corresponding rated breaking capacity of isolator. Such as on short circuit current, should choose corresponding with short-circuit making capacity of disconnecting switch.
Isolator, knife switch circuit characteristics were selected primarily on the basis of Circuit decision circuit number, contact type and number. Some products can be modified, manufacturing plant in a certain scope in order to meet the different needs.
The isolator, knife switch (including knife change-over switch ) products insulation voltage for the majority of AC 500V, 440V DC, so installation ( or knife switch knife switch ) circuit, shall not exceed the rated voltage of AC 500V or DC 440V. The calculation circuit current also should not exceed the rated current. Knife switch pole number, location and mode of operation can be selected according to the actual need.
When the knife switch direct on-off small load, should pay attention to choose the corresponding switching capability. Especially when direct control of small motors when the inductive load, consideration should be given to the switch on and off in the process of current characteristics ( such as the starting current, the starting time etc. ).
Isolator, knife switch on according to the above principle selection, required for the short circuit performance verification, to ensure the specific installation position on the prospective short-circuit current does not exceed the rated short-time withstand current of electrical ( when a circuit with short-circuit protection appliances may be rated ultimate short-circuit current ).
Fuse combined electrical equipment selection, required in the isolator, knife switch selects the request, and then consider the fuse characteristics. Fuse type knife switch high limit breaking capacity, mainly for the corresponding level of the switchboard and power box. General purpose load switch rated current not exceeding 200A, on-off capacity is 4 times of the rated current, can be used as industrial and mining enterprises in the power distribution equipment for manual, frequent operation, or as the end of the line short circuit protection. High breaking capacity load switch rated current up to 400A, limit breaking capacity up to 50KA, suitable for the occasion of big short circuit current.
Current knife switch has two major categories of products. One is the lever operating mechanism of the single throw or double throw knife switch. This knife switch can cut off the current rating of the load current, mainly used for low voltage power distribution device of switch board or the power box and other products. Belongs to this class of products HD12, HD13 and HD14 series single throw knife switch, as well as HS11, HS13 series double throw knife switch. Another kind is the central handle type single throw or double throw knife switch. This kind of knife switch can not breaking current, only as isolated power supply used in the isolator, mainly for the general control panel.
Commonly used load switch fuse combined electrical apparatus, (also known as the iron casing switch or steel shell switch ) has HH3, HH4, HH10D and HH11 series, the maximum rated current up to 400A, a diode and triode two forms. The switch casing are generally equipped with a door lock mechanism, when the door open switch not closed. Fuse type knife switch are mainly HR3, HR5 and HH11 series. The HR3 series RT series fuse and knife switch, with operating mechanism, a front operation before repair, repair and operation after the side before operation, repair and so on several structural layout, the maximum rated current 1000A. HR5 series to update the product design, using 32 series fuse, with spring energy storage mechanism, a phase failure protection function, the maximum rated current 630A. HR11 series with RT15 type fuse, spring energy storage type operating mechanism, single lever pull handle, the maximum rated current 4000A. 3
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