Specific Requirements

1.8.1 MCC shall comply with specification requirements indicated below:

cables, future additions of cables, ease and safe maintenance. Cable alleys shall be

provided with suitable hinged doors. Sheet steel barriers shall be provided between individual compartments of cable alley. This barrier shall be provided with the opening for power and control connections to any one circuit in the cable alley with the busbars and the adjacent circuits live.

1.8.3 For each vertical section a separate set of vertical bus bars shall be provided to Serve the modules.

1.8.4 The design of feeder trolley shall remain same for both single front and double single front and double front. Separate vertical busbars shall be used for each front. Identical feeder modules in both the fronts shall be interchangeable.

1.8.5 The outgoing feeder trolleys shall be fully drawout and shall have the following

features: It shall be possible to withdraw the trolley without having to unbolt or unscrew any power and control connections to the equipments mounted on the withdrawable trolley. Both power and control connections shall be drawout type. However incomer feeder may be of fixed execution.

1.8.6 Various compartment sizes in a vertical MCC panel shall be in multiples of a basic dimension. However the minimum module size shall be 200mm for switchfuse feeder and 240mm for contactor feeders.

1.8.7 The trolley withdrawal shall be by means of crank and screw arrangement or by movement on guided rollers. Plug in independent of manual force. Necessary clamping may be done to ensure all-round positive pressure on the drawout contacts once the trolley is plugged in. power drawout contacts shall be located towards the bottom position of each trolley. The trolley shall be lockable in fully plugged in position and devices shall be provided to ensure positive in. in test position power contacts shall be totally isolated and a device shall be provided for indication of test position.

1.8.8 All switch drives other than rotary switches shall be lockable in both ON and OFF positions. The switches shall be interlocked with the compartment door to prevent

opening of the door when the switch is in ON position. A defeat mechanism for this interlock shall also be provided.

1.8.9 The maximum height of the operating handles, etc on the panel shall not exceed 1900mm and shall not be below 300mm from the floor.

1.8.10 Unused modules in the panel shall be fully equipped with hinged door, power and control terminals for starter modules and cradle for future use.

1.8.11 All bimetal relays shall be separately mounted type with connecting links rated for the maximum rating of the contract in the Starter module.

1.8.12 Bimetal relays of various current ranges required for motors likely to be connected to a contactor must be identical in dimensions for interchangeability, else special mounting plate to mount different relays shall be provided.

1.8.13 Heavy-duty starters with saturable type CT operated relays shall be used for motors with starting time more than 15 seconds.

1.8.14 The feeders shall meet the requirement of type-II co-ordination as per IS 13947 1.8.15 All identical modules shall be interchangeable.

1.8.16 All switches or fuse switches shall be load break, heavy duty/motor duty air break type provided with quick make/break manual operating mechanism. The operating handle shall be mounted on the door of the compartment having the switch.

1.8.17 Fuses shall be pressure fitted, non-deteriorating HRC cartridge link types. Diazed fuses are not acceptable.

1.8.18 It shall be possible to handle the fuses during off load conditions with full voltage available on the terminals. Wherever required fuse pullers shall be provided. The fuse base shall be located in the modules to insert fuse pullers and insert or remove the

1.8.19 The contactors shall be AC3 rated, air-break type, equipped with three main contacts and minimum 2NO+2NC auxiliary contacts.

1.8.20 The coil of the contactor shall be suitable for operation on 240 V, 1PH AC supply and shall work satisfactorily between 65 to 110% of the rated value.

1.8.21 Bimetal relays shall be manually reset type with reset button brought out on the front of the panel. The reset push button shall be capable of being operated without opening the compartment door.

1.8.22 Bimetal relays shall be positive acting ambient temperature compensated type with adjustable setting range shall have built-in single phase prevention feature which operate even with 50% rated current at the time of single phasing.

1.8.23 Current transformers shall conform to IS2705. Protective current transformers shall have an accuracy class of “5P” and an accuracy limit factor greater than 10. Metering CT shall have an accuracy class of 1 and accuracy limit factor less than 5.

1.8.24 Current transformers shall be capable of withstanding the applicable peak momentary short circuit for 1 second and shall have a minimum rating of 10VA.

1.8.25 Voltage transformers shall be cast resin type and shall be provided with primary fuses. Miniature circuit breakers with auxiliary contact shall be provided on the secondary side.

1.8.26 All indicating instruments shall be of 96X96 mm-square pattern. All AC ammeters and voltmeters shall be moving iron type with accuracy class of 1.5 as per 1248. Ammeters for motor feeders shall have a non-linear compressed scale at the end to indicate motor starting current. Voltmeter shall be suitable for direct on line connection.

1.8.27 Pushbuttons for stop (Red colour stayput type) and reset (White) shall be provided on the front of the panel.

1.8.28 Cluster Led type indicating lamps shall be provided with translucent covers for ON, OFF and TRIP indications.

1.8.29 The switches, contactors and other power devices shall consider a margin of about 20% over the name plate current rating of the respective load.

1.8.30 Minimum of one NO and one NC spare contracts of all contactors & relay devices shall be wired to terminal block.

1.8.31 20% spare terminals shall be provided for each module.

1.8.32 For CT & VT circuits disconnecting type of terminals shall be provided . 1.8.33 Space heater with MCB & thermostat shall be provided for each vertical panel. 1.8.34 Necessary instrumentation for measurements of following parameters shall be provided for incoming feeders of 415 V MCC.

- 3 phase Current with selector - 3 phase Voltage with selector 1.8.35 Module Details

(a) Incomers

(i) The incomer modules of 415 V MCC shall be of switch fuse controlled. They shall be provided with

! One set of CT for metering ! Selector switches

! Ammeter ! Voltmeter

! Indication lamps for all three phases

(b)Feeders provided for supplying local control panels, power sockets etc., shall be provided with suitably rated switch & fuses .

(c) 240V, 1 phase, control transformer modules and space heating module shall be provided with incoming side switch, fuse, suitably rated 415/240V cast resin type

transformer (expected loads +30% margin) Secondary fuse, and supply indicating lamp and connection to the buses.

(d) Motor modules

(i) The motor modules shall be provided with ! On , Off and fault indicating lamps.

! Necessary auxiliary contactors for fault alarm circuit, 240V space heating circuit.

! Module on, off PBs for non reverible modules and forward reverse and ‘Off” PBs for reverseible modules.

! Appropriate circuitry for reciving the on , off and forward – reverse commands from remote panels / system , interlocks, On and Off command from local push buttons, etc.,

! Two pole MCB for space heating circuit.

ii) The motor modules rated above 22 kW shall be provided with 240V, 1 phase space heating arrangement.

iii) The modules for motors rated 18.5 kW and above shall have a CT The CT connection shall be so wired to the terminal block so that provision for remote current indication is available at the motor local push button station.

iv) Ammeters shall be provided on the panels for all motors rated above 18.5 kw.

v) Depending on the rating of the motors, the motor starter modules shall be designed as per the enclosed Electrical Design Engineering Basis data.

1.8.36 APPROVED MAKES OF COMPONENTS :-

1. Contactors, Bimetal relays, : - Siemens, L&T , Alstom/GE SFU , Fuses, timers etc

2. Numerical relays, Motor protection relays :- Alstom