Modernized Systems for 24 Solar Tower Tunnel Telescope at Kodaikanal N. SIVA RAJ 13-04-2007 Indian Institute of Astrophysics, Bangalore
24 Solar Tower Tunnel Telescope Kodaikanal ******* INAUGURATED by Dr. P. Subbarayan, ( Minister for Transport & Communications ) Govt. Of India on 14 th September 1960. ************************ GRUBB PARSONS Telescope - Coelostat - Control Systems Designed by Sir Howard Grubb Parsons & Co. Ltd, Walker Gate, England in May 1958 **************************** SCIENTIFIC ACHEIVEMENTS 46 Years Valuable Observational Data ***********************
Modernized Systems for 24 Solar Tower Tunnel Telescope at Kodaikanal H I G H L I G H T S * GRUBB PARSONS Control System * R.A and Dec. Fine Speed System * * Modernized Control System of the Telescope * * Coelostat Diurnal Drive & Tracking System * Modernized AC Synchronous Servo Motor Simovert Master Drive * * 15 Objective Lens Focus Control Drive * * Upgradation of Grating Mount & Drive Automation * * Electrical Rewiring of Telescope building * *****************
GRUBB PARSONS Control System Vaccum Tube Version of Electronics used in the System. Diurnal Drive consisted of thermostatically controlled oven and heater in the oscillator control circuit. R.A & Dec CW and CCW Coarse and Fine speeds, 15 Objective Lens, controlled through the system. The above System was completely discarded by replacing with our Modernized Control Systems on 12 th October 2006 Earlier Control System - Grubb Parsons, England
R.A and Dec Fine Speed System * Setting Speed of 1deg of arc/min of time * Guide Speed of 1 min. of arc/min of time, Became essential that still finer speed will be better for Sunspots Scanning. Coarse Speed AC Motors, Fine Guide Speed HS 50 RA & Dec (cw &ccw) EMC Coupling with Interlocking Circuit preventer & Audio/Visual Limits Indication. Integrated Mechanical Modular mount attachment developed by Mr. J.P.A.Samson. Observational Results: Fine speed movements in R.A & Dec the Image positioning accuracy has improved to less than 0.5 arc.sec. for Sunspot scanning with spacial finer steps. ( A.V. Ananth, Prof. Jagdev Singh, N. Sivaraj, K.C. Thulasidharen ) AC -Coarse & Stepper -Fine Motors Coupled with EMC
A.V. Ananth N. Sivaraj K.C.Thulasidharen A.V. Ananth N. Published Sivaraj in Academic K.C.Thulasidharen Report: 2003-04 Published in Academic Report: 2003-04
Modernized Control System of the Telescope Bin No: 1 R.A/Dec Coarse Control Drive, Limits, Interlock and Software Interface Bin No: 2 SS-2000 Superior Electric Slo-Syn Drive System Bin No: 3 Relay panel, EMC supply, +5v/+15v dc supply Bin No: 4 Variable Speed Stepper motor Grating Drive System Bin No: 5-15 Objective Lens Focus Control Drive Bin No: 6 Power Supply Dual 110v for SS-2000 drives and Dual 24v dc for the Electro-magnetic Clutch Modernized Control System for 24 Inch Solar Tower Tunnel Telescope
COELOSTAT DIURNAL DRIVE SYSTEM & TRACKING The Vaccum tube version of Diurnal drive was replaced with an advanced Solid State Drive System with higher accuracy in Finest Variable TWS tracking speed of the Solar image installed on 20 th December 1988. ( Prof. R. Srinivasan, K.S.Ramamoorthy ) Since then the Drive system is working exceptionally good except for the major problems developed with the AC Synchronous Motor due to ageing, a status where it can fail at any moment. The exact replacement of the motor is not available. Coelostat Diurnal Drive System Diurnal Drive Motor A.C Synch. Motor: H.P: 1/20, R.P.M: 1420, 200v, 3 Phase, Freq: 47 C/S, Make: Croydon, England
Modernized AC Synchronous Servo Motor & Simovert Master Drive Proposed SIEMENS System: A.C Synchronous Servo Motor with Incremental Encoder, Torque: 2.6 NM, R.P.M: 0 to 3000 rpm, Model: 1FK7042 5AF71-1AA0. SIEMENS SIMOVERT Master Drive/Converter: Power: 1.1KW, Input: 380 480 V AC, Model: 6SE7013 OEP50, Output Frequency / Max. digital resolution: 0 400Hz / 0.001 Hz = 0.1 rpm. The System has been procured and expected to be installed at KKL by the end of April 2007. Features planned: PC Control of Speed with GUI. PC Calculates the diurnal speed & sets the Synchronous Motor frequency accurately. Integrated GUI environment for R.A, Dec drives, focus control & Grating control. [ March 2008 ] ( Prof. R. Srinivasan, N. Sivaraj ) Modernized Version of Objective Lens Focus Control Drive Designed and fabricated Control drive for AC induction motor single phase running at constant speed of 1400 rpm incorporating AC magnetic solenoid brakes for instant stopping as soon as the forwarding and reversing of the lens is stopped. Keeps the Solar image precisely focused onto the focal plane, since the overshoot of the carriage moved in steps of 0.5mm is arrested by the shoes of an AC magnetic brake bearing, on the drum when the motor circuit is broken. The reduction gear box has a spring loaded slipping clutch torque of 0.6 lb.ins. on the end of the worm wheel, as a part of the carriage travel limiting device.
Upgradation of Grating Mount & Drive Automation ( Work in Progress ) Scope of Work * Fabrication of new mount for the Grating. * Replacement of existing gear system with more precision gear with zero backlash. * Mounting of Absolute Encoder on axis of rotation for position readout. * Modified Grating mount will have new Warm and wheel system. * Micro Stepping Slo-Syn drive - MD 808, Stepper Motor - KML 063 and 17 bit Absolute Encoder HEIDENHAIN ROC412 for accurate positioning. Planning, Preperations, Drawings and Preliminary works are in progress. Mr. P.U. Kamath from Mechanical Engineering Division is working on the new mount design & fabrication and myself working on the drive automation. The work is expected to be completed by end of December 2007. ( P. U. Kamath, N. Sivaraj )
Proposed Electrical Rewiring of Telescope Building * Ageing of Electrical wirings & frequent problems * Weak & broken Insulations * Rusted GI pipes & bad Earthings * Damaged light fittings. Requirements / Estimation and Proposal Submitted for approval. The above work is proposed to be carried out during September and October 2007.
With the Completion of Grating Drive Automation & Electrical Rewiring and Renovation of the building before the end of December 2007, I hope the 24 Solar Tower Tunnel Telescope becomes fully Modernized Telescope with Upgraded Scientific Observational Facilities. Thank You ************