Low voltage switchgear type VMK
The switchgear incorporates:
- apparatus cubicles and cable cubicles
- circuit-breaker cubicles disconnector cubicles
- transformer cubicles
The main busbars are located in a busbar compartment in the upper section of the cubicle. Vertical busbars are connected to these for supplying the apparatus cubicles. The apparatus is supplied from the vertical busbars located on the left and feed-out to the cable cubicle located on the right. The apparatus cubicles and cable cubicles are available in two depths. 325, 650 and 975 mm, with type designation VMK 3 and VMK 6 and VMK 9.
Characteristics
Optional erection
The switchgear can be installed as freestanding units or against a wall. For switchgear blocks for better erection basement construction from steel profile U6.5 is available.
Optional location of apparatus
The apparatus groups can be arranged in the apparatus cubicles in order of size or according to the operating sequence.
Supplementary
Apparatus groups can be easily replaced and reserve space can be easily utilised.
Simplified planning
All the apparatus cubicles have the same width and height. All apparatus groups have the same width adapted to the width of the cubicle. The modular heights vary depending on the size and function. Each cubicle accommodates a certain number of modules and it is a simple matter to calculate how many modularised apparatus groups can be accommodated.
Technical data
Standards
The switchgear fulfils the requirements of IEC 439 and conforms with FIE’s “Document 249/1972, Recommendations for the numbering of terminals”. Information regarding agreement with other standards will be supplied on request.
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Data
A complete constructional system for switch-gear and control gear includes a very large amount of components with many parameters which influence the technical data. The design and dimensions of specific equipment are also influenced by the existing operating conditions which are often unknown until relatively late during the planning stage. It is therefore meaningless to give detailed information in a catalogue of all the relevant performances and of the conditions under which they are applicable. It is for this reason that only certain rated data are specified here, sufficient to •enable the planning and calculation of a complete switchgear system. Further information on fully specified switchgear will be provided on request.
Diversity factor
| Number of outgoing units | Rated diversity factor as per IEC 61439 clause 4.7 |
|
| 2 - 3 4 - 5 6 - 9 10 and above |
0.9 0.8 0.7 0.6 |
Rated insulation voltage
| Busbar system | 1000V a.c. |
Rated currents, summary
Thermal rated current, VMK 6 with full busbar arrangement
| Enclosure to IP 21 | |
| Horizontal main busbars | 3200A |
| Vertical busbars for cubicles | 2100A |
| Partitions between horizontal busbars and between intermediate busbars and apparatus space reduce the rated current by approximately | 10% |
| Enclosure to IP 53 | |
| Value of rated currents reduced to approximately | 20% |
| Partitions as mentioned above and enclosure to IP 53 reduce the rated current by approximately | 30% |
Apparatus
| Circuit breakers | 4000A | |
| Discconectors | 4000A | |
| Mechanical switches | 1000A | |
| Blade-type fuses | 800A | |
| Starters | 1200A |
Short-circuit strength
| Of the horizontal busbar system with the maximum number of busbars in VMK6 | ||
| Peak withstand current | 120kA | |
| Short-time withstand current | 60kArms | |
| Strengthened with extra busbar holder | ||
| Peak withstand current | 175kA | |
| Short-time withstand current | 85kArms |
Arc-withstand strength
VMK switchgear has been tested successfully with arcs of 0.5s duration. Such tests are as yet not standardised.
Enclosures to IEC 144
| Normal version,without seals | |
| Self-ventilated | IP 21 |
| With seals | IP 53 |
| Extra | IP 54 |
Main dimensions of switchgear
| Cubicles | height [mm] |
width [mm] |
+bbc [mm] |
depth [mm] |
| VMK 3 | 2250 | 600 | 720 | 325 |
| VMK 6 | 2250 | 600 | 720 | 650 |
| VMK 9 | 2250 | 600 | 720 | 975 |
+bbc mean cubicle width + width vertical busbar compartment
NOTE: Cubicles height for 40M is 1930mm.
Width of adjacent cable cubicles, 296, 416 and 536 mm With side frame 328, 448 and 568 mm Internal space for installation of apparatus 48M or 40M (M=module) (1M=40 mm).
The design, data and dimensions are subject to modification without prior notice.
Description
Apparatus cubicles
The apparatus cubicles have a width of 600 mm, see summary of dimensions below. The cubicles consist of a framework with 2 sideframes of U-formed steel sections with two rows of holes in each flange. 2 trim plates and 2 kick plates. On the front the cubicles are fitted with hinged doors with locks which can be opened by separate door handles or a screwdriver. Each apparatus group normally has its own door. The rear of the cubicle can be open, covered with a rear panel or fitted with a door. The left-hand side is covered by a partition wall of insulating material, located on the left-hand side of the busbar compartment. The righthand side is open. The top is covered with a roof panel mounted 15 mm above the cubicle frame for ventilation purposes. In the event of an overpressure arising in the cubicle, both the rear panel and. the roof panel will be lifted without being: forced away from their attachments.
Busbar compartment
The vertical busbars are built into a separate compartment, located on the left-hand side of the cubicle. The busbar compartment consists of a side-frame, trim plates, kick plates and panels for the front and the rear. The roof panel is common to both the apparatus cubicle and the busbar compartment.
Cable cubicle
For connection of the apparatus groups a cable cubicle is used and this is placed on the right-hand side of the apparatus cubicle.. If the switchgear is of the free-standing type accessible from the rear. The rear space of the apparatus: cubicle can be used as a cable cubicle. Cables should not, however, be laid adjacent to the apparatus groups in the front of the apparatus cubicle. The cable cubicles are available in three alternative widths so that they can be adapted to the number and size of the cables to be connected. They are available with attachments and cable ducts. Side frames of adjacent apparatus cubicles are utilised for cable cubicles, However, a right-hand side frame is required for a cable cubicle which is positioned to the far right of a cubicle row.
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Busbar systems
Horizontal busbars
The horizontal busbars are placed in bus-bar holders in the upper section of the cubicle. A max. of two parallel bars per phase can be accommodated in VMK 3. In VMK 6 there is space for four parallel bus-bars per phase and. furthermore. up to tWo neutral busbars. VMG 6 is also available with two parallel busbar systems. each with two busbars per phase as in VMK 3. Sectionalising disconnectors can be supplied built into the horizontal busbar system.
Vertical busbars
The vertical busbars are available in four dimensions. They can be primary, i.e. connected to the horizontal busbars or secondary, i.e. connected to the horizontal bus-bars via a switch (if required combined with fuses) which then constitutes a main switch for the cubicle.
Branch connections from busbars
Busbar clamps with steel bases and copper-alloy uppers are used for making branch connections. The apparatus groups are connected with screws and bars with tapped inserts of steel. In both cases, high-grade steel screws with metric thread and with a tensile strength of 785 N/mm2 are used. Two sizes of screws are normally utilised. both having the same hexagonal socket head enabling them to be tightened with the same wrench. Screws that are to be loosened when changing apparatus groups are of the self retaining type.
Earthing and neutral busbars
An earthing busbar is located at the bottom of the cubicle and is attached to the cubicle frame. A neutral busbar, which is insulated from the cubicle frame, can also be located in the bottom of the cubicle adjacent to the earthing busbar. In VMG 6 with a single busbar system, one or two neutral busbars can be located in the upper section of the cubicle behind the phase busbars. Vertical busbars located in the cable cubicle are connected to the earthing busbar and neutral busbars for connection of neutral and earthing cables.
Equipment earth
Apparatus plates and apparatus are earthed through their fixing screws: doors through their hinges. Which are fastened with self-tapping screws. The hinges have serrated stainless pins. Apparatus mechanisms which are mounted on insulated bases are earthed with earthing conductors to the apparatus plate.
