Uilian José Dreyer

Dynamic Eccentricity Induced in Induction Motor Detected by Optical Fiber Bragg Grating Strain Sensors

Mechanical and electrical forces of a three-phase induction motor (TIM), in operation, can cause strain in the stator, which may lead to frustrating vibration problems. These problems may greatly reduce reliability and ultimately lead to increased maintenance cost. This paper shows the method to overcome this problem by carrying out the dynamic strain measurement analysis in a TIM running at no-load condition, using an optical fiber sensor. The dynamic strain induced by mechanical and electrical forces was measured by using fiber Bragg gratings (FBGs), installed inside the motor, in between two stator teeth. The electromagnetic immunity and reduced size of the FBGs render them suitable for this application. The frequency components of the strain in TIM were predicted using a model of the forces present in the air gap, considering static and dynamic rotor eccentricities. Two TIM motors, one of 2-poles and the other of 4-poles, and each equipped with two FBGs strain sensors, were used. The sensors were positioned between two stator teeth, separated by 120° from each other in the 2-pole motor and 90° in the 4-pole motor. The experimental analysis shows that the frequency components of the dynamic force spectrum presented by the two motors are the same as those predicted theoretically. Rotor eccentricity was achieved by attaching an unbalanced load to the rotor shaft. The amplitude of vibration at rotor rotational frequency increased when the unbalanced load on the rotor shaft increased. The measurement presented in this paper can be used to determine some TIM parameters, such as the effect of the motor power supply on its vibration signal. It can also be used as a potential maintenance tool for the continuous monitoring of the TIM with high sensitivity.

Vibration measurement of Induction Motor under dynamic eccentricity using optical fiber Bragg grating sensors

The vibration in Three-Phase Induction Motors (TIM) is due to mechanical and electrical forces existing during the motor operation. Vibration problems in induction motors can be extremely frustrating and may lead to greatly reduced reliability increasing the maintenance cost. The vibration was measured using fiber Bragg gratings (FBG) installed inside the motor between two stator teeth. The vibration frequencies in TIM are predicted using a model of the forces present in the air gap considering a static and dynamic rotor eccentricity. Two FBGs were positioned between two stator teeth, separated by 120° from each other. The analysis of the vibration spectrum at 60 Hz motor power supply presents the frequencies 60 Hz, 120 Hz, 180 Hz and 240 Hz. This combination of the mechanical and electrical frequencies continue to appear even when the motor electrical supply frequency is reduced by half. The measurement present in this paper can be used to determine some TIM parameters, like the effect of the motor power supply on its vibration signal and also be used like a potential maintenance tool for predictive purposes with high efficiency to continuously monitor the TIM.

Thermal and vibration dynamic analysis of an induction motor using optical fiber Bragg gratings

In this paper it is presented the results of temperature and vibration measurements in a Three-phase Induction Motor (TIM) running at no-load condition. Vibration and temperature analysis are the most successful techniques used for condition monitoring of induction motors. The vibration is measured using two FBGs installed inside of the motor between two subsequent stator teeth. The motor spectrum of vibration when power is at 60 Hz presents the frequencies 60 Hz, 120 Hz, 180 Hz, and 240 Hz as theoretically expected. For the temperature measurement two FBGs are encapsulated in an alumina tube fixed along the stator. The results show 0.9°C difference between the two FBG caused by the motor ventilation nearer of one FBG. These measurements can be used to determine TIM parameters and still be predictive maintenance tool.

A technique to package Fiber Bragg Grating Sensors for Strain and Temperature Measurements

This paper reports an effective method of packaging a fiber Bragg grating (FBG) for the simultaneous measurement of temperature and strain. The technique consists of embedding two fiber Bragg grating sensors inside a polymeric material with different geometrical characteristics. The mechanical and thermal characterizations of the optical transducer were performed. Then a matrix equation used measurements of the wavelength shifts from the two sensors and yielded information about the temperature and strain coefficients. The preliminary results demonstrate the feasibility of the encapsulation technique allowing measurements of temperature and strain in smart structures and harsh environments. The experimental procedure provides robustness to the sensor and the matrix equation approach has the potential to determine simultaneously the strain and temperature coefficients.

Optical fiber instrumentation of a high power generator and turbine

The instrumentation of a high power generator and its complementary systems including the turbine bearings is presented and discussed. The generator consists of a 175MW hydroelectric generator installed in the Salto Osório power plant in the southern region of Brazil. Results show good agreement with the already existing instrumentation and demonstrate the technology potential for a full optical fiber sensing system to monitor these large machines.

Photonic sensors: From horse racing to horse power

The use of photonic sensors to monitor horses is presented and reviewed. Results are very promising and can be used in other areas to monitor animals, machines or industrial processes.

Optical quasi-distributed simultaneous vibration and temperature sensing in stator bars of a 370-MVA electric generator

In this paper, we propose a new multiparametric optical fiber transducer applied to an electric generator of 370 MVA. The optical transducer has three multiplexed FBGs in the same optical fiber as the sensing element. The FBG sensors can simultaneously measure both the temperature and vibration independently of the other multiplexed FBGs. The installation in the power plant was performed using six transducers and it was obtained 23 hours of simultaneous vibration and temperature measurement. All the FBGs used to monitor generator vibration were able to monitor the frequency of mechanical and electromagnetic vibrations, which were measured at 2 Hz and 120 Hz, respectively. During the measurement, the machine was turned off due to a failure and all the FBGs sensed temperature changes, as well as frequency vibration changes. The largest temperature difference measured between the FBGs during the test is approximately 2°C.

Quasi-distributed fiber Bragg grating temperature sensors for stator bars monitoring of large electric generators

This work presents the application of a sensor based on quasi-distributed Fiber Bragg Gratings to monitor stator bars temperature of large electric generators. The applied FBG packaging method follows industrial standard procedures, and resulted in a robust and reliable sensing method, facilitating the future installation in the power plant. Experimental results are acquired in laboratory using the expected range of temperature values in the real machine. The measurement errors in the recorded results are within the calculated uncertainties and the time constant is shorter than what is obtained with conventional RTD for the same application.

Quasi-Distributed Temperature Measurement for Hydroelectric Generators Bearings via use of Fiber Bragg Gratings

This work presents a temperature sensor based on quasi-distributed Fiber Bragg gratings applied to hydroelectric power plants utilities. The calculated uncertainty of each FBG meets the requirements for temperature monitoring of hydroelectric generator bearings.