Modernization and performance data upgrading of high power electric motors at their repair process

The paper presents a possibility of improving perf ormance data and durability in exploitation of high power electric motors at their repair process. Some redesigning of the motors may be necessary. Examples of redesigned squirrel cage motor output up to 3200 kW are given. As a result increasing of durability for hard staring conditions (frequent or long lasting starts of the motor), diminishing the noise level or increasing of efficiency level of the redesigned motors were a chieved.W artykule przedstawiono możliwość znaczącej poprawy parametrów technicznych (w tym również trwałości eksploatacyjnej) silników elektrycznych dużej mocy, którą można osiągnąć w trakcie remontu. Do osiągnięcia tego konieczne są jednak pewne zmiany projektowo- konstrukcyjne w remontowanym silniku. Podano przykłady dla silników klatkowych mocy do 3200 k

Electric motors selection for middle and large capacity industrial drives

Selection of electric motors used in various kinds of industrial drives is realized at designing stage of that drives. But the exploitation condition of the machine not always can be properly foreseen at designing stage. And the exploitation condition (especially starting conditions) heavily influence electric motor’s working reliability. For middle and large capacity d.o.l. started induction motors the frequency and duration of their starts is of crucial importance for motor’s reliability. The motors for high frequency of starts and for long starting time (driving equipment of large inertia moment) should be specially designed. Proper design of the rotor cage for this motors is of high importance. Komel Center elaborated own methods and computer programs for designing rotor cages of large induction motors for heaviest starting conditions

Big capacity squirrel cage motors for frequently repeated or long lasting starts

High capacity induction squirrel cage motors used at different industrial driver are usually started by switching direct on line. Starting current, several times higher than nominal load current, causes thermal and mechanical, dynamic stresses dangerous for motor's structure. Both, stator and rotor windings are endangered at starting period, but stresses in rotor cages are usually considerable higher, therefore rotor design (and its manufacturing process) is of high importance for motor's durability

Assurance of high reliatibility for middle and high power induction motors at their design stage

The cost of an unexpected failure of a large AC motor can be very high. Not only the cost of simple repair (or replace) of the failed motor, but the costs of production breakdown should be taken into consideration. Many of the motor failures may be avoided by careful and proper motor design, especially by propper design of stator winding and its insulation system, bearing housing and bearing selection, rotor squirrel cages. At Komel Centre evaluation and calculation methods of mechanical and thermal stresses occurred in rotor cages of different types (deep bar, double cage, idle bar) at motor starting period are developed. The calculation are verified by special bench tests. The objects of the tests were sample AC motors 315, 500 and 800 kW, 6000 V. The same was performed for stator winding overhangs for 2 and 4-pole 6000 V motors. Very helpful in design process of reliable AC motors are case studies and expert evidences of different motors breakdowns and failures occurred at their exploitation. At Komel Centre many expert evidences of failed large AC motors of variouos manufacturers were carried out (see table 1)

Adjustment of squirrel cage motors to long lasting or frequently repeated starts

Induction squirrel cage motors used in many industrial drives, even of high capacity, are started by switching direct on line. Starting current, several times higher than nominal load current, causes thermal and mechanical, dynamic stresses dangerous for motor's structure. Both, stator and rotor windings are endangered at starting period, but stresses in rotor cages are usually higher, therefore proper rotor design (and its manufacturing process) is of high importance for motor's durability. Examples given in the paper show, that even standard motor with new, special, redesigned rotor can withstand as many as 70.00 long lasting starts, executed by switching the motor direct on line

Rule of Law Crisis, Judiciary and Competition Law

This article discusses the implications of the rule of law crisis on a core area of EU law: competition law. It analyses the reforms of the judiciary in selected EU Member States and the reaction of EU institutions. The article shows that the reforms of the judiciary give rise to doubts regarding the independence and expertise of courts which are responsible for reviewing the decisions of national competition authorities adopted under Articles 101–102 Treaty on the Functioning of the European Union (TFEU) and national competition laws. As a result, the effective judicial protection required by EU primary law is undermined. In addition, mutual trust, upon which the decentralized enforcement of EU competition law is based, is put into question. The article calls upon EU institutions, and in particular the European Commission, to monitor closely the developments in Member States which may affect the enforcement of EU (and national) competition rule

Ventilated ODP motors shaftheights 200 through 355 mm, an economical alternative to totally enclosed ones

Design and operating properties of ventilated (open drip proof) induction squirrel cage integral HP motors compared to totally enclosed fan cooled (TEFC) ones. In Europe TEFC motors are regarded as more reliable and better withstanding any environmental hazards. In US the approach to ODP motors is different, ODP motors are regarded as standard. In Poland manufacturing of ODP integral HP motors was abandoned in the 60-70 of the last century. Actually a new series of ventilated ODP motors of shaftheights 200-355 mm have been designed by KOMEL Centre. The motors, IEC degree of protection IP23, will be manufactured by two polish companies. Main features of the new motors incl. test results of 315 kW motor are presented