Aldo Boglietti

A Critical Approach to the Iron Losses in Induction Motors

Since induction motors represent the more consistent electrical motors used in industrial environment, the increase of the induction motor efficiency represents a crucial aspect to obtain a consistent energy saving. In the USA, from 1997 the electric motor producers have to build high efficiency motors in according to the protocol promulgated by the Energy Policy Act (EPACT). This protocol defines the minimum value of the efficiency for general purpose, 2 or 4 poles, 400V, 50÷60 Hz, three-phase induction motors with a rated power in the range 1÷200 HP [1]. In Europe, the European Committee of Manufacturers of Electric Machines and Power Electronics (CEMEP) has realized a similar protocol to which the electric motor producers can to agree in voluntary manner [2]. An increase of the motor efficiency means a reduction of the loss contributions. The total motor losses can be divided in the stator and rotor Joule losses, in the iron losses and in the mechanical losses. A viable way to improve the efficiency of an induction motor is the reduction of the iron loss contribution, because this choice does not require a complete change of the magnetic sheet shape. A possible solution for getting a strong reduction of the iron losses could be the use of good quality magnetic materials (with specific iron losses in the range 2.7÷3.5 W/kg at 1.5 T) instead of the low or medium quality magnetic materials typically used in general purpose induction motors (with specific iron losses from 5.3 W/kg up to 8.0 W/kg at 1.5 T). In a previous paper [3], the authors have shown that a reduction of the magnetic material specific iron losses does not produce the expected iron loss reduction.

Modern Heat Extraction Systems for Power Traction Machines—A Review

This paper presents a review of modern cooling system employed for the thermal management of power traction machines. Various solutions for heat extractions are described: high thermal conductivity insulation materials, spray cooling, high thermal conductivity fluids, combined liquid and air forced convection, and loss mitigation techniques.

Induction motors field oriented control based on averaged parameters

This paper exposes the performance of field oriented control for induction motors drives based on average motor parameters, rather than individual ones. The average parameters for a group of industrial motors of small size (7.5 kW, 50 Hz, 4 poles, 380 V) have been evaluated, with reference to field oriented control. Averaged field oriented controls based on the mean values of motors parameters, obtained by statistical analysis or from motor data sheets, have been set up. Test criteria, chosen to evaluate the control performance, are presented and discussed.<<ETX>>

Power derating for invertor fed induction motors

The aim of this work is to give a contribution to find a simple methodology for defining a power derating index for invertor-fed induction motors. The theoretical and experimental work has put in evidence the possibility of defining a derating coefficient using only no-load tests performed with a sinusoidal square wave and PWM invertor supply. The defined derating indexes for each invertor supply are verified by means of load tests performed on a motor equipped with thermal sensors to measure the copper and iron temperatures. In addition, for the PWM supply, the effects of the modulation index on the motor efficiency are also considered.<<ETX>>

A Statistical Analysis of the Induction Motors Produced by Italian Electromechanical Companies on the Base of the Efficiency Frame Proposed by the Cemep Agreement

The reduction of energy consumption through an increase of electrical system energy efficiency is now an important target for every countries. This choice allows to reduce the CO2emission and other pollution sources due to electrical energy production. Making reference to the European Union, typically 60%-80% of energy absorbed by industrial sectors and 35% of energy absorbed by commercial sectors are due to electrical motors. In the industrial field, a motor consumes an annual quantity of electricity which approximately corresponds to 5 time its purchase price, throughout its whole life of around 10—12 years [1]. The electrical motors are by far the most important type of load. They are used in all the sectors in a wide range of applications, such as: fans, compressors, pumps, conveyors, mills, winders, elevators, transports, home appliances and office equipments. Since the motors are the larger users of electrical energy, even small efficiency increase will produce very large energy saving in the European Union. These concepts are not new, but their importance has assumed an important role across the end of the seventies and the start of the eighties, with the well known energetic crises. Even if the Italian people remember just the “by foot Sunday”, those years saw the blossom of national proposals linked to a much more rational use of the energetic resources, with a particular reference to every type of energy saving. Making reference to the Italian approach, it is important to underline the “Progetti Finalizzati Energetica I and II” which put together the competencies of the academic and industrial people with very interesting results.