NATIONAL ALUMINIUM COMPANY LIMITED - Rites

• By-pass pass arrangement shall be provided to operate the motor in case of failure in
frequency converter.
Thyristor converter
• Minimum ratings of thyristor cells
• PIV rating : 2.5 times the peak value of line voltage
• dv/dt rating : 200V/microsecond for voltage control and
1000V/microsecond for inverter control.
• di/dt rating : 100A/ microsecond.
Protective features
• AC line surge suppression net network
• Under voltage in supply network
• Phase sequence protection and monitoring
• RC snubber network across each thyristor cell
• Thyristor fuse failure
• Under voltage in Dc line
• Over voltage in Dc line
• Over speed monitor
• Over load
• Earth fault
• Instantaneous over current
• Transformer fault
• Cooling fan failure – Stall monitor for motor Alarms
Above condition shall be annunciated. Following warning signals shall also be provided as
minimum in addition to above.
• Motor fault (winding / bearing te temperature, vibration) as applicable
• Loss of frequency command
• Meters, Switches, Lamps
Following shall be provided as minimum meters:
• Input volt meter and ammeter with selector switches
• Output voltmeter and ammeter with selector switches.
• Output frequency ncy meter
• Selector switches, pushbuttons, and lamps as required.
• kW meter for drive ratings above 200 kW Regulation and controls
Control facilities shall include following but not limited to:
• Reference speed setter
• Ramp generator
• Speed feed back
• Current feed back
• Trigger module
• Pulse transformers
• Logic control module
Technical Specification:Sec-6, Electrical
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