Thermal Analysis of an Induction Motor

Motors & Generators with MotorSolve

Temperature is an important factor that affects the performance of electric machines. Due to their thermal design, electric machines can suffer problems such as insulation breakdown, reduction in torque provided, shortened lifetimes and so on. In addition, the size of a motor is ultimately dependent upon the thermal rating. In order to predict machine temperatures, the design of the electric machine needs to take thermal factors into account. In this example, a 4kW IM machine is chosen to demonstrate the new thermal analysis features within MotorSolve.

Induction Motor

METHODS and RESULTS

INDUCTION MOTOR MODEL SPECIFICATIONS

The chosen machine is a standard cage induction motor with the following rated performance. Power of 4 kW, current at 9 A, voltage of 380 V, frequency is 50 Hz, and a speed of 1,435 rpm. It is a 4-pole motor with 36 stator slots and 28 rotor bars. The temperature class of the stator winding is 311 degrees F (155 degrees C).

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THERMAL MATERIALS

The materials chosen for each component in the machine will have a significant impact on the thermal response of the machine. The left image shows the user-interface for how the user assigns materials to each component. Obtaining accurate magnetic and thermal properties for each material must be a high priority for the user, as the accuracy of the material's character can impact the machine response significantly.

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MOTOR HOUSING & COOLING

Besides the thermal materials, the housing dimensions, cooling configuration and interface gap settings also affect the thermal analysis results.

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PREDICTING the TEMPERATURE in the MOTOR

Set different operation conditions and run a transient thermal simulation to compute and present the component temperatures. The result is determined according to the maximum temperature of each component throughout the entire transient simulation.

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LOSSES for THERMAL ANALYSIS

The sources of the heat include various losses such as the copper losses, iron losses, etc. The results show all the various losses. The winding and rotor cage losses are the main contributors to the heat.

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DUTY-CYCLE LOSSES

Losses in a machine will often change as a function of time. The user can specifiy how the losses vary in the form of a Duty Cycle. The image shows the results a Duty Cycle with a 25 minute interval repeated throughout 150 minute solution time. Further note that the simulation used 2 coupled magnetic- thermal iterations. The temperature and corresponding heat source are shown in separate plots.

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DUTY-CYCLE TEMPERATURE

Corresponding to the Duty Cycle losses results, the temperature plot is shown as the image.

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