Roland Reekmans

Audible noise and losses in variable speed induction motor drives with IGBT inverters-influence of the squirrel cage design and the switching frequency

This paper describes a large number of experiments comparing audible noise, losses and efficiency of different induction motors supplied by an IGBT inverter. The influence of the switching frequency on the motor behaviour is analysed. As a comparison the motor is also supplied directly from the mains. Furthermore two different motors are compared to study the influence of the rotor cage design on the motor behaviour. It is shown that the choice of the switching frequency has a large influence on the audible noise produced by induction motors. By taking higher switching frequencies, the time harmonics move to a nonaudible region. At some higher switching frequencies subharmonics appear, having a bad influence on the audible noise. At higher fundamental frequencies the audible noise of the fan dominates. The switching frequencies can cause pure tones that are very disturbing to the human ear. The influence of the switching frequency on the efficiency is rather small. Minimal overall losses appear around 3 and 4 kHz. The voltage-frequency ratio should be taken constant from the point of view of the efficiency.<<ETX>>

Losses, audible noise and overvoltages in induction motor drives

Experiments are performed to analyse the influence of the Volt/Hz ratio and the switching frequency on losses, both in inverter and motor, audible noise of the motor and overvoltages. The effect of the squirrel cage design is investigated. The cable between motor and inverter is varied to minimise the overvoltages.<<ETX>>

Microcomputer-controlled torque calculator in DC drives

The indirect method for torque measurement in DC drives is presented. The microcomputer-controlled device calculates the torque from a voltage, a current, and a speed signal, using some preliminary stored values of parameters and characteristics. To avoid the temperature dependency of the resistance, the electromotive force (instead of the terminal voltage) is indirectly measured using a so-called electromagnetic force bridge. Experimental results prove the accuracy and the convenience of this method. It is concluded that the greatest merit of the indirect method consists in the fact that no mechanical impact on the installation is necessary. >

Using multimedia in variable speed drive teaching

Abstract The paper provides ideas and practical experiences using multimedia at the electrical engineering department in the field of electrical machines and variable speed drives. Using multimedia develpments, it is possible to confront students in a more attractive and efficient way with Electrical Machines and Drives. The paper approaches the term multimedia from different points of view The definition of a multimedia computer is explained and different authoring systems are presented. A practical example, visualisation of phenomena and construction of a squirrel cage induction machine, is looked at in a closer way. The conclusion is that the undergraduates gel more interested and even recommend additional multimedia applications in other topics of electrical engineering education.

Influence of Switching Frequency and Squirrel Cage Design on Audible Noise and Losses in Variable Speed Induction Motor Drives with Transistor and IGBT Inverters

AbstractA large number of experiments are performed to analyse the influence of the inverter type and the switching frequency on the audible noise, losses and overall efficiency in induction motor drives. Temperature measurements both in stator and rotor give an indication of the required derating, if any. Results for a standard design motor, consecutively supplied by a transistor based inverter and IGBT inverter are compared with the behaviour when the machine is directly connected to the mains. To analyse the influence of the rotor design, a special rotor with no current redistribution is constructed and mountedin a rewound stator. Higher switching frequencies have a large influence on audible noiseand temperature, but the overall efficiency remains nearly constant. However the distribution of losses is influenced.