BANGLADESH POWER DEVELOPMENT BOARD TENDER ... - BPDB

The main power supply shall have a short circuit capability of 50 kA.All electrical equipment shall conform to the appropriate IEC.All motors, controllers, auxiliary apparatus and conduit shall be substantiallygrounded to the structural parts of the crane.(1) Motors :All electric motors shall be of the wound rotor, drip-proof, protected type andtropicalized. They shall be in accordance with the latest edition of IEC Standardfor crane motors.(2) ControllerThe controllers shall be readily accessible for maintenance and inspectionpurposes. The nominal 415 volts, three phase, 50 Hz power supply from the maincollectors shall be controlled by means of a suitable manually operated main aircircuit breaker located in the operator's cab.The main power supply breaker shall be identified by a nameplate instructing theoperator to open the breaker when leaving the cab upon completion of work.a. Bridge and Trolley TravellingThe travel motion of the bridge and trolley shall be controlled by the normalmethods of acceleration, reversing and plugging the motor. Multi-pole contactorsmay be used.Within limits of each required speed, the drive shall be controlled to providesubstantially uniform speed regardless of load. The control shall include allnecessary relays, timers, and limit switches required, for smooth and safeoperation.b. Hoisting and Lowering ControlThe hoist drive shall be controlled to provide substantially uniform speed on eachmaster switch step regardless of load.(3) Main Circuit ContactorA main circuit contactor shall be provided in common for main power supplycircuit of main and auxiliary hoists, and for bridge and trolley travel.The main circuit contactor shall be controlled manually by a pushbutton switchlocated in the operator's cab and it's control circuit shall have necessaryinterlocking circuit as follows, but not limited to these.(4) Master SwitchThe master switches for the main hoist, auxiliary hoist, trolley travel, and bridgetravel shall be on the cam operated type, with a contact operating mechanism toensure, positive operation of the contracts in both directions. Contacts shall bedouble break, spring-operated, readily renewable without disturbing the wiringand with automatically adjusting fingers to reduce wear.Ghorasal 200 MW to 300 MW Gas Turbine Peaking Power Plant Project (Vol-2 of 3)134