Sunit Kumar Saxena

A novel hybrid low cost controller for maintaining low input current harmonic over wide range of load conditions for power factor corrected boost AC to DC converter

With growing usage of switching power supplies, there has been excessive injection of current harmonics on AC power supply networks. Various agencies world-wide have framed benchmark for maintaining current harmonic distortion. Boost power factor corrected (PFC) converter is the most popular front end converter in power supplies. For medium to high power applications, average current mode control technique is used for controlling boost PFC converter. This technique works very well at near rated load conditions; however, if load drops down to a fraction of rated load, input current harmonic distortion increases considerably. A novel hybrid controller is proposed here which maintains low input current harmonic distortion over wide range of load conditions. The proposed hybrid controller dynamically switches between average current mode and transition or critical mode control (CRM) depending upon load conditions. The proposed hybrid controller provides a cost effective solution for applications having space and weight constraints, using low cost commercial off the shelf (COTS) integrated circuits (IC). Implementation of the proposed hybrid controller is illustrated here and experimental test results are recorded.

Novel exciter circuit for ignition of gas turbine engines in aerospace applications

Ignition Exciter System (IES) convert electrical energy at low voltage levels into high intensity sparks capable of firing an air fuel mixture in gas turbines. Generally, electronic switches are in series with the energy discharge path of the spark current. It requires bulky storage capacitor to account for the excessive loss in the series switches. These configurations reduce energy transfer efficiency, and lead to bulkier ignition exciter system. Proposed ignition exciter topology is designed to improve efficiency, reduce real estate and weight; which are major requirements of a high energy discharge system in space constrained environments such as in aerospace applications. Proposed topology makes an effective utilization of key characteristics of passive circuit elements in the formation and sustaining high energy spark. The spark formation circuit consists of an inductive element, utilized to generate high voltage pulse; sufficient enough to initiate an arc. The spark sustaining circuit consists of capacitive element, supplying only the spark energy once the igniter plug becomes conductive. The proposed circuit topology promises to meet the requirements of spark energy delivery into the spark plug at drastically reduced peak current levels. The proposed topology promises higher system efficiency, reduced part count and thus shall reduce the product cost, while making the overall ignition exciter system more reliable. This paper provides the proposed IES circuit design, parameter selection and circuit simulations results for 28VDC to 20kVDC, 18kW peak power IES system.

A novel AC-AC converter with minimum snubber requirement

Matrix converters inherently have problems with commutation which are generally mitigated by using snubbers. Problem of commutation also places a limitation on their voltage transfer ratio. In this paper, a new high frequency linked AC-AC converter topology is proposed which ensures reliable commutation, taking care of parasitic inductances, with minimum snubber on the input side. A simple switching algorithm to achieve this is also suggested. The topology has the flexibility to improve the voltage transfer ratio of a conventional matrix converter while maintaining unity power factor on the input AC side. Simulation results support the feasibility of the scheme.