Multi-motor drive system (MMDS) offers the advantage of modularity over a single-motor drive for high-power, medium voltage applications. However, connecting a large number of motors to the same mechanical shaft may lead to torsional oscillations. Thus, a dual-motor drive system (DMDS) where two motors of equal power ratings are coupled together, can be a good compromise to bring some modularity without creating unnecessary mechanical problems. Moreover, a DMDS can offer benefits other than just modularity. A torque-sharing strategy between the individual motors of a DMDS is developed in this paper. At rated load, the two motors are required to share the torque equally. However, at reduced load, the ratio in which the two motors share the load-torque is a design parameter for the DMDS. In the present work, this parameter is optimized in order to minimize the total copper-loss occurring in the drive. The torque-sharing strategy is validated through experiments on a motor drive consisting of two 3.7 kW induction motors coupled to a common mechanical shaft.

High-power, medium-voltage squirrel cage induction motor (SCIM) drives used for railway traction application are invariably operated with low inverter switching frequency in order to curb the switching energy losses. Carrier-based synchronous PWM techniques are very popular in such cases. Here, the carrier frequency (fc) is continuously varied such that its ratio with the frequency of the modulating signal (fm) remains constant. This ratio is defined as the Pulse number (P). Open-end winding induction motor (OWIM) has been recently established as suitable replacement for the conventional Y-connected SCIM drives specially for railway traction application. It has been established that OWIM drive offers more flexibilities in the choice of P. In this paper, the impact of orientation of the triangular carrier with respect to the modulating signal on the machine line-currents harmonics in analysed using double-fourier series. Double fourier series is used to calculate an appropriate phase-shift between the carrier signals of the two inverters of OWIM drive to improve the line-current THD further. The analytical findings are validated both through simulations as well as experimentally.

Wound-Rotor Induction Machines (WRIM) are extremely popular for high-power applications both as industrial motor drives and generators for harvesting wind-power energy. However, these machines suffer from a major drawback due to the use of slip-rings which require frequent replacements because of mechanical damage. Cascaded WRIMs are slowly becoming popular as an alternative for the conventional WRIM drives. In the inverse connected cascaded configuration, the rotors of two WRIMs are both mechanically coupled and electrically connected in reverse phase-sequence. This completely eliminates the need to use slip-rings as the rotors are not required to make electrical connections with any stationary circuit. However, both the modelling and control complexity of such a machine increases considerably. This paper aims to provide a simple model for an inverse connected cascaded wound rotor induction machine (ICC-WRIM) in the rotor frame of reference (FOR). The choice of the reference frame is justified in the paper. Further, a torque estimation technique using only the sensed stator currents is proposed. The validity of the developed model and torque estimation technique is established experimentally on a 7.4 kW laboratory prototype of an ICC-WRIM.

An improved vector-controlled drive for three phase squirrel cage induction motor is proposed in this paper. The proposed scheme is based on the concept of indirect field oriented control of induction motor using rotor flux orientation and is intended for a proportional integral controller based current controlled induction motor drive in the stationary reference frame. The proposed scheme helps in reducing the current tracking error including phase error and magnitude error in the above current controlled induction motor drive. This is achieved by adding an additional feedforward term, in addition to the back emf compensation and resistive voltage drop, in the existing state of the art technology for implementing a vector controlled induction motor drive in the stationary reference frame using proportional integral current controllers. The proposed algorithm is validated in simulation and hardware using a fractional horse power squirrel cage induction motor coupled to a dc generator.

A modified current controlled drive is proposed for three phase squirrel cage induction machine. The drive is implemented in the stationary reference frame using proportional resonant type of current controllers. The proposed drive controls the motor currents over one fundamental cycle and is based on the steady state model of the vector drive with rotor flux orientation. This offers two advantages. First, it becomes possible to formulate the close form expressions for the alpha axis and beta axis stator current references which is not possible in a dynamic model based implementation. Second, the overall control algorithm becomes simplified and all the divisions are eliminated. The proposed drive is validated both in simulation and hardware using a fractional kilowatt squirrel cage induction motor coupled to a dc generator.

In this paper, we propose a novel methodology for dynamic optimization of process quality control and maintenance planning while considering the real-time health state of the system. First, by investigating the relationship between product quality and tool degradation, a new tool condition monitoring (TCM) system for instantaneous diagnostic and prognostic is proposed. Subsequently, the existing process quality control policy is enhanced to become dynamic and extended to deal with machine deterioration with time. This is done via the proposed residual-life based evaluation and multistate magnitude of process shift schemes. Furthermore, the maintenance planning model is modified to capture real-time remaining life information. These models are integrated and built in conjunction with developed TCM system. As a result, the designed dynamic integrated model can evolve itself to re-evaluate the optimal values for the design parameters used in the entire lifecycle of the manufacturing process. Finally, an experimental case study is implemented to demonstrate the practical feasibility of the developed methodology. An extensive performance investigation revealed substantial economic benefits over conventional independent approach. This is further complimented with systematic sensitivity analysis. Moreover, we attempt to present potential implications and guidelines for various industrial scenarios to expand the model's robustness and relevance in industrial environment.

Current minimization is the widely used optimization technique for control of IPM motors that optimizes the torque per current ratio and the copper losses of the motor. In this paper a simplified current minimization technique for direct torque controlled IPM drives is proposed by utilizing a normalized look up table that is independent of motor parameters. The implementation strategy also includes the effect of field weakening, both due to the operation of the the motor above rated speed and due to a reduction in the dc-link voltage. The control strategy is supported by simulation results and demonstrated experimentally using a 2.5 KW IPM motor.