The Laboratory Analysis of the Thermal Processes Occurring in Low-Voltage Asynchronous Electric Motors

Łukasz Nogal,Piotr Łukaszewski,Łukasz Sapuła,Andrzej Magdziarz,Radosław Szreder,Désiré Dauphin Rasolomampionona

doi:10.3390/en14082056

Łukasz Nogal, Piotr Łukaszewski + Show 4 more

Open Access

https://doi.org/10.3390/en14082056

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Abstract

The exact nature of thermal processes occurring in an electric motor is often unknown. Thus, the estimation of temperature rise using mathematical models and computational experiments is becoming increasingly important. Thermal analysis is the key design aspect, which has become significant in the design process for electric motors. The thermal analysis of electric motors can be helpful in developing effective thermal monitoring methods. This analysis is crucial for a better understanding of the overall performance and failure prevention for these electrical motors. In this paper, laboratory investigations of thermal processes in low-voltage asynchronous motors are described. The analysis of the results leads to the conclusion that the classic single-exponential models do not match the dynamically changing thermal processes in electric motors especially in the case of intermittent motor operation.

Highlights

The energy supplied to electric machines and drive systems constitutes a significant part of industrial electrical power consumption
The analysis of the results, in particular, dealing with the motor’s intermittent operation, confirms that the time constantof the various elements of the machine, which is proportional to the specific heat, depends on temperature
The results for the measurement of temperatures of the selected motor elements clearly show that the thermal time constant is a function of temperature

Summary

Physical Tests

In order to perform an appropriate analysis of dynamically changing thermal processes occurring in electric motors, a defined set of tests will be needed. Considering the simplest case of heating up the motor stator windings, they can be where winding resistance (Ω), treated Rasu —stator a homogeneous body of thermal power, which is equal to the power losses. T—the thermal time constant of the motor, ranging from several to tens of minutes (s), and θu—temperature at which to determine the winding current flow during long-term value. Taking into account the initial condition θ = θp (fort = 0), we can solve Equation (2) in order to obtain the relationship that specifies the change in temperature of the winding as a function of time:. Equation (5) is the basis of the temperature measurement algorithm (motor rithm (motor warm-up process) used in the thermal design of many digital relays.

First-Order Thermal Model

Second-Order Thermal Model

Equivalent

Results and Proposed

Conclusions