The power control & Motor control centre is totally enclosed with dust and vermin proof modular construction , self supporting ,floor mounting air insulated cubicle type for use on 415/440 Volts 50 Cycles AC supply.
The panel shall be designed for operation in high ambient temperature and high humidity tropical atmosphere conditions. Sufficient provisions are made to facilitate inspection, cleaning and repair for installations wherein continuity of operation is of utmost importance.
// Construction: :
- Switchboards are fabricated from TATA Stealium Panel grade CRCA Sheet Steel, with load bearing members and doors of 2mm thick, and partitions of 1.6mm thick. Gland plates generally with 3mm thick sheet is used.
- Switchboards are totally enclosed with Complete dust and vermin proof using neoprene gasket. Degree of protection is not less than IP-52as per IS: 2147.
- Feeder and cable alley doors are provided with lift off concealed type hinges to maintain proper line and ease of operation.
- All hindged doors earthed with 2.5 sq mm green straned cooper flexible wire to the main frame.
- Functional unit such as circuit breakers /starters/ MCCB is arranged in multitier - formation.
- Panels are suitable for the specified condition in specification.
- Knockout holes of adequate sizes with rubber grommet is provided in proper location for wire connection.
- Panel shall be made of requisite vertical sections, which when coupled together shall form continuous dead front switchboards.
- The PCC & MCC shall be readily extensible on both sides by the addition of vertical sections after removal of the end covers.
- Lifting lugs are provided to lift the board/panel.
- Removable type 3mm gland plates are provided at the bottom of panel.
- The structure of panel is mounted on base frame of 3mm thick Sheet steel or on ISMC base Channel frame of 75x40x5mm. This design shall ensure that weight of the panel is adequately supported.
- The general construction confirm to IS-8623 for factory built assembled switchgear and control gear for voltage up to and including 1100V AC.
// Busbar :
- The busbar is air insulated and made of high conductivity, high strength Aluminum alloy, complying with the requirements of Grade E91E of IS: 5082 or E.C. grade copper.
- Depending upon the specification , busbar shall be air insulated and made of high conductivity , high strength , electrolytic grade, Aluminum / Copper of Grade E91E of IS: 5082.
- Depending upon the specification, busbar are in rectangular cross section suitable for carrying the rated full load current in separate busbar chamber with bolted covers.
- Current density is generally 0.8 A per sq.mm for aluminum & 1.6 A per sq. mm for copper.
- These bus bar’s are supported with non-hygroscopic epoxy / SMC supports at suitable intervals in order to withstand the dynamic forces of short circuit at 50/7OKA RMS Symmetrical for 1 sec.
- Bus bars are processed i.e. cutting, punching & bending is done in most modern hydraulic machine to avoid any burr, break etc.
- Copper Bus bars are always electrolytically tinned to avoid any oxidation & improve conductivity.
- Suitable clearances and creepage distances provided on the adequate size of Bus bar system to minimize the possibility of fault as per the relevant Indian standard.
- The main bus bar has continuous uniform current rating throughout the length of each Power Control Centre and the neutral busbar has a continuous uniform rating of 50% of the phase bus bar, unless otherwise specified.
- All the connection is done by cadmium plated high tensile bolts.
- For proper identification, the Bus bar and inter connection are insulated by color coded heat shrinkable sleeve of 1.1 KV grade Red, Yellow, Blue for phases and Black for Neutral .
- Continuous earth strip of required size is provided inside each shipping section at bottom, interconnected by bolt.
Powder coating Process
- Complete steel structure used in construction of Switchboards is thoroughly cleaned to remove all rust, scales, grease and other foreign matters. This is done through extensive metal treatment of the sheet by Eight Tank process as per the IS: 3618.
This treatment consists of Degreasing, Rising, Phosphating, &Passivation.
The sheet steel is then given a coat of highly corrosion resistant primer and then the same is coated to the specified shade as per IS: 5.
Generally thickness of the coating is not less than 120microns and after the coating the structure is baked in temperature controlled oven for 1hour in 200”Celcius to ensure proper bonding.
Different tests like peel off, rupture, etc are carried out for better quality of the powder coating.
PH value of the chemical used in the tanks for the treatment is checked periodically to maintain proper concentration of the chemicals.
Cable Termination and Control Wiring Process :
- Cable entries and terminals shall be provided in the switchboard to suit the number, type and size of Aluminum power cables and copper control cables.
- Provision shall be made for top or bottom entry of cables as required. Generous size of separate cabling chambers shall be provided with ample space for cable glands and terminals such that cables can be easily and safely terminated.
- All control wiring shall be carried out with stranded copper conductor of 1.5 sq.mm. PVC insulated wires of 1.1kb grade..
- Wiring shall be neatly bunched, adequately supported and properly routed to allow for easy access and maintenance.
Wires shall be identified by ferrules at each end and terminals would be provided with marker.
Prabhat Group © 2017. Developed and Managed by SME Business Services Ltd.
