The second year Electrical and Electronics Engineering students, and three faculty members of PSG Institute of Technology and Applied Research visited M/s Transformers and Electricals Kerala Limited, Cochin on 20thAugust 2016.
Doordarshan (DD) is an autonomous Government of India founded public service broadcaster. It is one largest terrestrial television networks in the world. Doordarshan HPT, Cochin, Kerala receives the programs from Delhi through satellite INSAT 3A&4B, mainly DD Cochin broadcast DD1 and DD news. The programs from Delhi studio are received as broadcast quality microwave/ Very High Frequency (VHF) signal through Parabolic Dish Antenna (PDA) receivers. The DD Cochin has high power transmitter (HPT) and low power transmitter (LPT). In HPT, video and audio carriers can be generated, modulates and amplified separately, combined in the diplexer at the transmitter output. But, in LPT audio and video signals are modulated separately but amplified jointly. The received program signals are amplified and filtered using exciter arrangement of 10 kW capacities. It consists of 6 amplifiers each of 2 kW capacities. Among, the 6 amplifiers, first 5 amplifiers are used for video signal processing and 1 for audio signal processing. The Amplitude Modulation (AM) technique is for video signal processing with the video carrier frequency of 224.25MHz. Similarly, the audio amplifier uses Frequency Modulation (FM) technique with Audio carrier frequency of 229.75MHz. The Vestigial Side Band Transmission (VSBT) method is used for broadcasting the program, which limits the number of channels in the spectrum allotted for TV. There are two types of transmitters are in use; they are Rohde and Schwarz which is for DD1 and NEC for DD news. The transmitter mast is generally has a height of 150 mts. It has two transmission stages i.e. lower band (LB) and upper band (UB). The entire process requires 60 kVA Uninterrupted Power Supply (UPS) and Automatic Voltage Regulator (AVR) arrangement. The exciter arrangement and transmitter cable are maintained in a air-conditioned room and with moisture remover arrangement to avoid disturbances in the broadcasting signal. Interactive session with the Doordarshan engineers has increased the student's confidence.
Transformers and Electricals Kerala Limited (TELK) is located in Angamaly near Kochi, Kerala. TELK manufactures Extra High Voltage Power Transformers (upto 315 MVA, 420 kV) and other equipments (CT, PT, Bushings) up to 420 kV class. TELK has an extra high voltage test laboratory for conducting all routine and type tests for EHV Power Transformers, Instrument Transformers, Bushings, Tap changers etc. The laboratory facility includes testing incoming materials, inprocess tests, in-house calibration, and transformer oil laboratory to test moisture content. During this visit, the students saw materials used in transformer manufacturing, and making of transformer coils and mounting structure. They are able to differentiate high power voltage and current transformers assembly and operating principle. They have also learnt about the testing of transformers and cooling material used in the transformers.