Modernized Systems for

24” Solar Tower Tunnel Telescopeat Kodaikanal

N. SIVA RAJ 13-04-2007

Indian Institute of Astrophysics, Bangalore

24” Solar Tower Tunnel TelescopeKodaikanal

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INAUGURATEDby

Dr. P. Subbarayan,

( Minister for Transport & Communications )

Govt. Of India

on 14th September 1960.************************

‘GRUBB PARSONS’Telescope - Coelostat - Control Systems

Designed by

Sir Howard Grubb Parsons & Co. Ltd,

Walker Gate, England

in May 1958****************************

SCIENTIFIC ACHEIVEMENTS46 Years Valuable Observational Data

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Modernized Systems for

24” Solar Tower Tunnel Telescopeat 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 *

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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

12th 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

Published in Academic Report: 2003-04A.V. Ananth N. Sivaraj K.C.Thulasidharen

Published in Academic Report: 2003-04

Modernized Control System for 24 Inch Solar Tower Tunnel Telescope

Modernized Control System of the Telescope

Bin No: 1 – R.A/Dec Coarse Control Drive, Limits, Interlock and Software InterfaceBin 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

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 20th 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************