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Nowadays, electric motors and frequency converters have a great variety of applications. In motor feedback systems, communication is performed over separate sensor cables, which are notable for their high cost. Power line communication (PLC) over the motor cable is a promising and cost effective alternative. In this paper, a communication concept based on PLC and direct sequence spread spectrum (DSSS) channel access method is presented for motor cable communication. The channel characteristics and noise in the channel of a laboratory test setup are studied. Effect of the frequency converter output and switching frequencies on the channel noise are investigated. Capacitive and inductive signal coupling methods are evaluated and compared first theoretically by measurements and analysis of channel characteristics, and then practically by data transmission tests carried out in the laboratory test setup. Software-defined radios (SDRs) are used as the data transmission devices for the communication concept evaluation. Concept's performance against variation of a signal-to-noise ratio (SNR) and switching frequency of the converter are evaluated. The concept applicability limits and optimal settings are presented. It can be stated that the concept provides a wider application range, than available solutions and can be effective for motor monitoring and speed data transmission. [ABSTRACT FROM AUTHOR]

The authors' research group is developing a mobile sensor for operation inside combustion chambers of big industrial power plants. The aim of developing the ball-formed sensor is to measure process information inside big combustion chambers (heat power over 100 MW), hopefully mainly from places which cannot be reached by ordinary measurement equipment outside the chamber. The sensor ball needs means for communication during operation. In order to provide a reliable communication link through the extreme harsh conditions, one must clarify the basic phenomena inside combustors, especially electromagnetic noise and attenuation. According to measurements, attenuation at frequency band 2-18 GHz is ~10 dB/m. [ABSTRACT FROM AUTHOR]

Microwave‐based measurement can provide new methods and practical solutions for the challenging task of measurement inside large industrial combustion chambers. In order to measure or communicate inside a combustion chamber using microwaves, the spectrum of background noise at microwave frequencies must be known. This study investigates the basic electromagnetic spectrum in flames, concentrating on microwave frequencies from 0.1 to 19 GHz. The study introduces, as reference values, known results from forest flames and flames in controlled environments. The focus of the work is the level of background noise at microwave frequencies and the impact of this noise on radio communication inside the combustion chamber. The effects of the microwave radiation levels are compared with the requirements of practical communication systems such as Bluetooth and narrowband ISM (industrial, scientific, medical) systems at 800–950 MHz. [ABSTRACT FROM AUTHOR]