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Heating calculation on a three-phase asynchronous machine

Heating calculation with ANSYS

Branch : Electrical engineering/electronicsSpecialist field: Electromagnetics, Heat Transfer

SCHOTTEL is the world leader in marine propulsion and control systems. CADFEM calculated the heat generation in ANSYS for a three-phase asynchronous machine.

Summary

Task

In three-phase asynchronous machines, heat loss is generated both by the current flowing through the stator windings and by induced currents in the short-circuit bars of the rotor. Hysteresis losses also contribute to heating. An FE simulation will provide the time-dependent heating and the temperatures reached at critical points.​

Solution

The averaged heat generation rates from the EMAG simulation are transferred into a 3D thermal FE model. Thermal transition points between the components are modeled as contacts. Finally, the simulation provides the time-dependent heating behavior of the entire machine body.

Customer benefits

The time-dependent 3D simulation in ANSYS describes the heating process of the entire machine body using Joule's heat without the need to produce complex prototypes.

Project Details

Task

SCHOTTEL GmbH in Spay supplies, among other things, marine propulsion systems based on three-phase asynchronous machines in the 2-5 MW power range. In such machines, heat losses are generated both by current flow in the stator windings and by induced currents in the rotor's short-circuit bars. Hysteresis losses also contribute to heating. Cooling is provided by the surrounding sea water through the bronze housing as well as the hollow bronze shaft through which the current flows. In addition, cooling air is forced into the winding head spaces and through air ducts in the stator and rotor lamination stacks. An FE simulation will provide the time-dependent heating and the temperatures reached at critical points.


Customer Benefit

The time-dependent 3D simulation in ANSYS describes the heating process of the entire machine body using Joule's heat without the need to produce complex prototypes.


Solution

The solution takes place in two steps:

1) 2D transient EMAG simulation
The determination of the heat generation in the stator windings is relatively simple via the given phase currents and the ohmic resistance. However, the current density distribution in the short circuit bars of the rotor is determined by electromagnetic induction. Through a 2D-electromagnetics simulation with ANSYS/Multiphysics, the current and flux density amplitudes as well as the resulting heat generation rates are calculated from the stator rotating field and the given speed or slip values. Due to the principle of the asynchronous machine, a complete transient condition must be simulated before the steady-state values can be extracted. This requires many time steps. It is shown that the concrete shape of the sheet metal cuts has a considerable influence on the current density distribution.

2) 3D transient thermal simulation
The averaged heat generation rates from the EMAG simulation are now transferred into a 3D thermal FE model. In this model the winding heads as well as the short-circuit rings are also designed in detail. Thermal transition points between the components are modeled as contacts. Convection and heat transport are represented by means of SURFACE and PIPE elements via key figures. The simulation finally provides the time-dependent heating behavior of the entire machine body.


Business Development
Dr. rer. nat. Martin Hanke

Products applied in the project