Air-gap Torque Method Research Articles

A non-intrusive technique for estimating the efficiency of low voltage three-phase induction motors

This paper introduces a non-intrusive technique based on the air–gap torque (AGT) method to estimate the efficiency of induction motors (IMs). The technique uses a 3rd-degree equation to calculate the sum of windage and friction losses (FWL) and rotor stray load losses (SLLr), considering the number of IM poles. IM speed is estimated using motor current signature analysis, and a new procedure to estimate stator resistance is presented. Efficiency is then determined by applying the estimated rotor speed, stator resistance, and the sum of FWL and SLLr in the AGT equations. This method requires only nameplate information, IM line voltages, and currents. Simulations and experimental tests for balanced, unbalanced, and harmonic feeding modes show the proposed technique’s estimated efficiency values are very close to measured values, unlike the AGT method. This demonstrates the proposed technique’s high accuracy, making it suitable for non-intrusive efficiency estimation of in-service IMs in industrial programs.

In-Situ Efficiency Estimation of Induction Motors Based on Quantum Particle Swarm Optimization-Trust Region Algorithm (QPSO-TRA)

The accuracy estimation of induction motors’ efficiency is beneficial and crucial in the industry for energy savings. The requirement for in situ machine efficiency estimation techniques is increasing in importance because it is the precondition to making the energy-saving scheme. Currently, the torque and speed identification method is widely applied in online efficiency estimation for motor systems. However, the higher precision parameters, such as stator resistance Rs and equivalent resistance of iron losses Rfe, which are the key to the efficiency estimation process with the air gap torque method, are of cardinal importance in the estimation process. Moreover, the computation burden is also a severe problem for the real-time data process. To solve these problems, as for the torque and speed-identification-based efficiency estimation method, this paper presents a lower time burden method based on Quantum Particle Swarm Optimization-Trust Region Algorithm (QPSO-TRA). The contribution of the proposed method is to transform the disadvantages of former algorithms to develop a reliable hybrid algorithm to identify the crucial parameters, namely, Rs and Rfe. Sensorless speed identification based on the rotor slot harmonic frequency (RSHF) method is adopted for speed determination. This hybrid algorithm reduces the computation burden by about 1/3 compared to the classical genetic algorithm (GA). The proposed method was validated by testing a 5.5 kW motor in the laboratory and a 10 MW induction motor in the field.

Non-Invasive Method for In-Service Induction Motor Efficiency Estimation Based on Sound Acquisition

Induction motors (IMs) are present in practically all production processes and account for two-thirds of the energy consumption in industrial settings. Therefore, monitoring them is essential to prevent accidents, optimize production, and increase energy efficiency. Monitoring methods found in the literature require a certain level of invasiveness, causing some applications to be unfeasible. In the present study, a new completely non-invasive method implemented in an embedded system performs the embedded processing of the sound signal emitted by an in-service IM to estimate speed, torque, and efficiency. Motor speed is estimated from the analysis in the frequency domain using the Fourier Transform. Torque and efficiency are estimated from the speed and motor nameplate information. To perform the tests and validate the proposed method/system, a workbench with a controllable torque was used. The workbench was also equipped to allow the results to be compared with the airgap torque method. The results indicate a high accuracy for the nominal load (error of approximately 1%) in the measurement of the efficiency and torque, and a mean relative error of 0.2% for the speed.

Comparison among Methods for Induction Motor Low-Intrusive Efficiency Evaluation Including a New AGT Approach with a Modified Stator Resistance

Induction motors consume a great portion of the generated electrical energy. Moreover, most of them work at underloaded conditions, so they have low efficiencies and waste a lot of energy. Because of this, the efficiency estimation of in-service induction motors is a matter of great importance. This efficiency estimation is usually performed through indirect methods, which do not require invasive measurements of torque or speed. One of these methods is the modified Air-Gap Torque (AGT) method, which only requires voltage and current data, the stator resistance value, and the mechanical losses. This paper approaches the computation of a modified stator resistance including the mechanical losses effect to be applied in the AGT method for torque and efficiency estimation of induction motors. Some improvements are proposed in the computation of this resistance by using a direct method, as well as the possibility to estimate this parameter directly from the nameplate data of the induction motor. The proposed methodology only relies on line voltages, currents, and nameplate data and is not intrusive. The proposed methodology is analyzed through simulation and validated through experimental results with three-phase induction motors. Also, a comparison of methods for in-service induction motors efficiency estimation is presented for the tested motors.

Implementation and Deployment of an Intelligent Industrial Wireless System for Induction Motor Monitoring

Three-phase induction motors (TIMs) are present in most industrial processes, accounting for more than 60% of the energy consumption in industry. Despite their importance in the productive sector, few motors are properly monitored, mainly due to the high cost of the monitoring equipment and the invasiveness in their installation. This paper presents the implementation and deployment of an industrial wireless sensor network (WSN) to monitor three-phase induction motors. Embedded systems were developed to acquire signals of current and voltage from sensors installed in the motors' terminals, perform local processing to estimate torque and efficiency, and transmit the information through the WSN. The method used to estimate the variables is based on the air-gap torque method. Before the deployment in the industry, experiments were performed to validate the system in laboratory. Finally, the system was employed in a real industrial environment, where different analyses and diagnosis of three motors running were performed. Using the proposed system, the efficiency versus load curves of the motors could be obtained continuously, and an energy loss analysis due to the oversizing of the motors was performed.

Efficient energy management measures in steel industry for economic utilization

Abstract The application of energy efficient Induction Machines (IM) is explained in reference to power consumption savings. In energy efficient IM, losses for various Horse Power (HP) ratings are summarized for bringing effective changes in design. Emphasis is laid on how load factor, speed & power quality affect machine’s efficiency. Replacement of conventional IM of higher power rating is done with required energy efficient Doubly Fed Induction Machine (DFIM) to enhance the performance at variable speeds near rated power outputs. Results of the proposed approach will give substantial savings in energy & loss reduction. The field data of Jindal Steel Rolling Mill (JSRM) at Hisar, Haryana (India) is taken into consideration. This paper proposes a non-intrusive air gap torque method for efficiency estimation of in-service IMs. This approach gives results considering stray-load and friction-windage loss according to IEC standard and IEEE112-B standard. The proposed method is validated experimentally whose effectiveness is witnessed using MATLAB/SIMULINK.

A Proficient Approach for Monitoring Induction Motor by Integrating Embedded System with Wireless Sensor Network

In this paper aims at monitoring parameter of induction motor like current, voltage, torque and efficiency in real time by employing embedded system with wireless sensor networks. An embedded system is employed for acquiring electrical signals from the motor in a noninvasive manner, and then performing local processing for torque and efficiency estimation. The values calculated by the embedded system are transmitted to a monitoring unit through an IEEE 802.15.4-based Wireless Sensor Network (WSN). At the base unit, various motors can be monitored in real time. The Air Gap Torque (AGT) method is used to find out the torque and efficiency in induction motor. It is used to measure efficiency in a much less invasive manner. The AGT method can be employed without interrupting the motor operation and it is not based on the motor nameplate. This method generally is more accurate than the other methods. The proposed model has a supervisor (PC) which Communicates with the remote terminal unit, processing the variable parameters and controlling the systems. The Receiver Terminal Unit (RTU) is a local controller in distributed processes environmental which acquires the data from sensors, process the collected data puts the required data together, forming the frame for transmitting to the Supervisory Controls (S.C). RTU also receives and processes Control commands from S.C. and executes them accordingly. The communication utilizes a full duplex communication for data transmission between S.C. and RTU. The communication through wireless by using Zigbee.

A Proficient Approach for Monitoring Induction Motor by Integrating Embedded System with Wireless Sensor Network

In this paper aims at monitoring parameter of induction motor like current, voltage, torque and efficiency in real time by employing embedded system with wireless sensor networks. An embedded system is employed for acquiring electrical signals from the motor in a noninvasive manner, and then performing local processing for torque and efficiency estimation. The values calculated by the embedded system are transmitted to a monitoring unit through an IEEE 802.15.4-based Wireless Sensor Network (WSN). At the base unit, various motors can be monitored in real time. The Air Gap Torque (AGT) method is used to find out the torque and efficiency in induction motor. It is used to measure efficiency in a much less invasive manner. The AGT method can be employed without interrupting the motor operation and it is not based on the motor nameplate. This method generally is more accurate than the other methods. The proposed model has a supervisor (PC) which Communicates with the remote terminal unit, processing the variable parameters and controlling the systems. The Receiver Terminal Unit (RTU) is a local controller in distributed processes environmental which acquires the data from sensors, process the collected data puts the required data together, forming the frame for transmitting to the Supervisory Controls (S.C). RTU also receives and processes Control commands from S.C. and executes them accordingly. The communication utilizes a full duplex communication for data transmission between S.C. and RTU. The communication through wireless by using Zigbee.

Comparison of Two Methods for Full-Load In Situ Induction Motor Efficiency Estimation From Field Testing in the Presence of Over/Undervoltages and Unbalanced Supplies

Numerous techniques with different levels of intrusion and accuracy have been proposed for in situ efficiency estimation. Among them, optimization-based techniques and the air-gap torque (AGT) method show promise when unbalanced supply conditions exist. In this paper, an optimization-based algorithm is proposed for in situ efficiency estimation of induction machines operating with over-/undervoltage and unbalanced supplies. In addition, a comprehensive study is done on the functionality and accuracy of the nonintrusive AGT method which is claimed to be one of the most promising methods in the literature. It is shown that the efficiency calculated by this method under field conditions cannot be used in the decision making process on replacement of the existing machines as well as the relevant calculations regarding the payback period. The research is supported by experimental results on two different induction machines.

Verification of the modified AGT method applied to determining efficiency of squirrel-cage induction motor

Verification of the modified AGT method applied to determining efficiency of squirrel-cage induction motor The modified air gap torque method to determine the efficiency of squirrel-cage induction motor was presented. of testing which continues the authors' work on application of AGT method to estimating induction motor's efficiency are discussed. The proposed method is verified in a number of selected low-power motors.

In-Service Efficiency Estimation with the use Modified Air-Gap Torque Method for Squirrel-Cage Induction Motor

Energy-efficient industrial drives and control systems are designed to minimize power consumption. Energy consumption is associated with the efficiency of energy conversion in electric motors. In the paper the nonintrusive efficiency estimation method for induction cage motor was shown. The implementation of the method was based on the air-gap torque method. The results were compared with those obtained with the classical air-gap torque method. The authors present a significant impact of estimation of mechanical power losses in the engine on the accuracy of estimating the coefficient of efficiency cage induction motor. Ill. 7, bibl. 24, tabl. 3 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.114.8.696

Energy-Efficient of Non-Invasive Motor for On-Line Monitoring System Based on Reasoning Model

This paper mainly introduces the development process of energy-efficient of non-invasive motor for on-line monitoring system based on reasoning model. In addition, the function , composition and commissioning of shis system is introduced. In this system, in order to collect and analyze status recording of the motor running, operating parameters of motor speed, torque and power factor, efficiency are estimated on-line by using motor stator current signal feature analysis technology. In the paper, air-gap torque method is used to non-invasive electromotor for efficiency computation. The designing process of software for On-line monitoring system is shown as: Firstly, monitor motor’s operating parameters on-line, then, motor energy management is supported by the analysis of monitoring recording. At the same time, construct communication network for motor monitoring by using wireless communication technology about efficiency curve of industry motor. This system has the advantages of monitoring precision, easy installation, low costs, especially suitable for monitoring and energy management of efficiency for small and medium-sized motor, and it has been used widely in industrial production.

Field assessment of induction motor efficiency through air-gap torque

Induction motors are the most popular motors used in industry. This paper further suggests the use of the air-gap torque method (see J.S. Hsu et al., ibid., vol.10, no.3, p.471-7, 1995) to evaluate their efficiency and load changes. The fundamental difference between Method E and the air-gap torque method is discussed. Efficiency assessments conducted on induction motors under various conditions show the accuracy and potential of the air-gap torque method.