Mini Sreejeth

Efficiency optimization of vector controlled induction motor drive

In this paper an efficiency optimization algorithm for vector controlled Induction Motor (IM) Drive has been developed and the performance of the IM Drive under different operating conditions has been analyzed. The controllable electrical loss in IM Drive is minimized by the optimal control of direct axis (d-axis) stator current, which controls the magnitude of rotor flux. Thus, the efficiency of the motor is optimized by weakening the rotor flux, which in turn reduces the core losses. The implemented algorithm is tested under different operating conditions of IM Drive including sudden change in load, commanded speed and equivalent circuit parameter variations of IM and performance of the drive under dynamic condition is analyzed in detail.

Development of supervisory control for distributed drives system

Continuous monitoring and control of motors and drives have become a need of process industries, which require operation of various drives in a pre-designated sequence. The programmable logic controllers (PLCs), an intelligent device, can realise automated operation. Distributed control system has partially autonomous local computational capability, interconnected through a digital communication link and coordinated by a supervisory control and data acquisition (SCADA) system. The resulting system has the advantages of local as well as centralized control. This paper describes the methodology, implementation, operation, monitoring and control of distributed drives with PLC and SCADA system. The performance of the drives are studied and analyzed for starting and load perturbation.

PLC based automated liquid mixing and bottle filling system

Automating repetitive tasks in the industries increases the productivity; reduces the probability of error and maintain product quality. Traditional methods of mixing fixed quantities of different types of liquids and filling them in bottles involve manual mixing of the constituent components based on measurements and bottling of the mixture as desired. Manual handling of such tasks is time consuming; expensive and often lack consistency in product quality due to human errors. A Laboratory Prototype of a Programmable Logic Controller (PLC) based automated liquid mixing and bottle filling system is designed to automate the control and mixing of two different liquids in predefined proportion and filling the generated mixture in bottles to achieve quality control; reduce human intervention and improve productivity. The mixing system draws fluids from two storage tanks and mix them in a user selectable pre-defined proportion and stores the mixture in an overhead reservoir. The bottling system transfers the mixture from the overhead reservoir to conveyor fed empty bottles based on the user defined ladder logic. The developed laboratory prototype of the automated system has housekeeping features; which include high and low level liquid indicators; emergency alarm for warning the operator and automatic stop features etc.

Sensitivity analysis of induction motor performance variables

The effect of parametric variations in three phase induction motor such as stator resistance, rotor resistance, leakage and mutual inductances on the induction motor performance variables such as input power, output power, stator current, starting current, magnetizing current, power factor, efficiency, developed torque and starting torque have been analysed. A nonlinear polynomial of the induction motor is derived and solved for determining the slip using computational methods to estimate the realistic value of slip of the induction motor at different load conditions. The designer of high performance drive system requires the knowledge with changes in parameters. Sensitivity analysis of machine performance variables is carried out to predict the performance affected by parameter variations through mathematical and computational methods. The analysis is carried out using the equivalent circuit of induction motor, where core loss resistance is omitted and also using the exact equivalent circuit of the induction motor, where the core loss resistance is considered.

Estimation of stator resistance in sensor-less induction motor drive using MRAS

Model Reference Adaptive System (MRAS) based estimation of stator resistance in a vector controlled induction motor (IM) drive is presented in this paper. The developed algorithm utilizes voltages and currents in synchronously rotating reference frame for the estimation of stator resistance thus reducing computational complexities as compared to the other estimation methods based on flux calculations. The algorithm used for stator resistance estimation is independent of speed. The estimated stator resistance is used for evaluation of rotor speed. The developed model is simulated using Matlab/Simulink and the dynamic responses of the IM drive are analysed for different operating conditions. The developed algorithm is stable in all four quadrants of operation including operation at low speed as well as zero speed.

PLC based power factor correction of 3-phase Induction Motor

A Programmable Logic Controller (PLC) based power factor correction method for a 3-phase Induction Motor (IM) through switching of shunt capacitors is proposed in this paper. A 3 phase IM has a low power factor (pf) at no load as it draws large magnetizing current and the active power delivered to the motor is low, which is utilized to overcome the no-load losses. The PLC based power factor improvement algorithm is developed and implemented on a 3 Phase laboratory prototype IM coupled to a DC generator and the effectiveness of the algorithm is tested under no-load and loaded condition. Based on the instantaneously measured value of power factor, the PLC switches the appropriate bank of capacitors into the circuit depending on the load condition to improve the pf. Large scale use of PLC in industrial automation, adaptability, simple implementation and economics justified its selection as the switching controller. A significant improvement in power factor under different loading conditions is observed.

Implementation and analysis of PLC SCADA controlled closed loop four quadrant speed control of chopper fed DC motor

In this paper, a scheme for closed loop speed control of DC motor in four quadrants using Programmable Logic Controller (PLC) is discussed. The armature voltage is varied using a Class E chopper circuit. The individual switches in the chopper circuit are switched using Pulse Width Modulation (PWM) control signals generated by PLC. Duty cycle of PWM signals are varied by PID controller of the PLC. Three main modes of operation have been implemented: Speed control mode, sinusoidal input tracking mode and step input tracking mode. The resulting current, voltage and speed waveforms are recorded on Digital Storage Oscilloscope(DSO) and analyzed. Speed, set point and control variables are observed on GUI made using SCADA software.

Distributed Drives Monitoring and Control: A Laboratory Setup

A laboratory setup of distributed drives system comprising a three-phase induction motor (IM) drive and a permanent magnet synchronous motor (PMSM) drive is modeled, designed, and developed for the monitoring and control of the individual drives. The integrated operation of IM and PMSM drives system has been analyzed under different operating conditions, and their performance has been monitored through supervisory control and data acquisition (SCADA) system. The necessary SCADA graphical user interface (GUI) has also been created for the display of drive parameters. The performances of IM and PMSM under parametric variations are predicted through sensitivity analysis. An integrated operation of the drives is demonstrated through experimental and simulation results.

Implementation of supervisory control system for PMSM drive

This paper presents an implementation of automation scheme for control of three phase Permanent Magnet Synchronous Motor (PMSM) drive. Performance evaluation and monitoring of drive is described using Supervisory Control and Data Acquisition (SCADA) and Programmable Logic Controller (PLC) system. The control, operation and monitoring of PMSM drive in three basic modes, i.e. position, speed and torque modes is achieved through PLC programming and SCADA. A Human Machine Interface (HMI) control is also developed for operation of drive system at field level controls. Ladder logic programs according to desired control mode of operations are developed to control and monitor the status of PMSM drive. SCADA screens have been developed to control and monitor the status of the motor and for field level control HMI touch screens are designed. The real time data related to PMSM drive such as output of position encoder, torque developed by motor, power input to motor, speed etc. are accessed for supervisory control of drive.