RECENT DRDO DEVELOPMENTS
Advanced Automotive Electrical System for MBT Arjun
The Combat Vehicles Research & Development Establishment (CVRDE), Avadi, has developed Advanced Automotive Electrical System (AAES) for MBT Arjun. It is a state-of-the-art technology development programme with a processor-based control for the complete hull electrical system, MIL STD 1553B bus, touch screen display, data logging, and BITE capabilities. The system gives emphasis on optimum performance with better man-machine interface. With the use of this system, the crew will experience reduced fatigue levels and can concentrate on their primary role in a battlefield.
The system consists of Pentium processor-based dual controllers, viz., the hull controller with remote terminal units at engine and driver stations. It also includes driver's instrumental panel with electro- luminescent touch screen display, master relay box, etc. The engine's and driver's remote terminal units are identical. In case the active controller fails, the stand-by controller handles processing along with data communication without affecting its performance. Both the hull and the display controller remote terminal units control the function of the engine, automatic transmission, ancillary motors. fans, lamps and integrated fuel level monitoring of all the tanks, including the nose fuel tank.
Variable Speed Constant Voltage and Frequency Generator for Aircraft
The CVRDE, Avadi, has also developed a 1 kVA, 400Hz, 200VL-L Variable Speed Constant Voltage and Frequency Generator in consultation with Indian Institute of Technology (IIT), Madras. The heart of the system is a brushless induction generator (BIG). This doubly-fed machine is based on the principle of cascade connection, i.e., output of one machine is transformed as input to the other machine and both the machines are mounted onto the same shaft. The stator has single winding on which excitation winding and power winding are
Constant voltage is obtained by controlling the magnitude of excitation current as a function of speed. Constant frequency is obtained in the 3-phase inverter using pulse width modulation technique. In the present system, constant voltage is obtained in the first stage by controlling the excitation, while in the second stage, this constant voltage is rectified and converted to desired frequency in the microcontroller-based inverter .
The stator has a single winding for p-poles and q-poles. The p-pole winding is used as excitation winding and the q-pole winding as power winding. The excitation winding and the power winding are electrically and magnetically de-coupled from each other. The rotor consists of caged nests and is designed to respond to the magnetic fields of both the p-pole and q-pole windings. A closed-loop controller has been developed, fabricated, and tested. This controller is able to adjust the excitation of the generator so as to maintain the DC terminal voltage constant at 215V .The control scheme has been implemented using analog devices.
The brushless induction generator has a simple and robust form of rotor construction. The elimination of slip rings and rotating diodes allow the machine to operate at high speeds and act as a high frequency generator. Elemination of slip rings also enables maintenance-free operation. Since the excitation winding and the power winding are parts of the same winding of different tappings, reduction in space is achieved. At CVRDE, these generators with their controllers are being tested on LCA.