Integration Principles and Thermal Analysis of an Oil-Cooled and -Lubricated Permanent Magnet Motor Planetary Gearbox Drive System

Abstract

A permanent magnet traction motor integrated with a planetary gearbox is studied. A machine of this kind can be employed as a propulsion motor in off-road machines like agricultural tractors that have to produce either very high traction forces at low speeds or reach higher traveling speeds at lower torques. In principle, a constant power curve as a function of speed is desired, which means that the output torque of the drive system should be inversely proportional to the operating speed of the off-road machine. Such driving conditions are challenging as the electric motor has to be heavily overloaded at the lowest speeds. Therefore, it is essential to accurately evaluate not only the electromagnetic performance but also the thermal performance of the machine. This paper studies the integration principles of an electrical machine and a planetary gear. The integration poses some new challenges to the design. For example, also the lubrication and cooling can, and, in practice, must be integrated into the system. The thermal performance of the motor and cooling with the lubrication oil of the gear were analyzed. The long-term tests with the oil cooling system were carried out to verify the successful integration.

Improved Thermal Modeling and Experimental Validation of Oil-Flooded High-Performance Machines With Slot-Channel Cooling

“…In the end-winding region, particular attention should be paid to the Nusselt number determination [29]. Different formulas are used to calculate corresponding to different parts in the end-winding region [37,38]: near the stator, near the stator winding, near the rotor. Equation ( 18) is applied to the heat transfer between the stator and the flooding oil, while equations ( 21) and ( 22) are applied for the convection heat transfer between the rotor/floodingoil, and between the end-winding surfaces/floodingoil.…”

A New Traction Motor System With Integrated-Gear: A Solution for Off-Road Machinery

“…The value of q = 0.5 offers high torque production but produces a poor torque quality with high torque ripple. 2) The air-gap leakage factor with q = 0.43 is moderate, σ δ = 0.83 resulting in a moderate stator leakage inductance which is now desirable as the field weakening range is not wide because the gearbox is to be used [22], [24]. 3) Also the operating harmonic (ν = 7) winding factor is acceptably high, k w = 0.902 resulting in low Joule losses.…”

“…The nozzles are placed so that the coils above the oil level will be flushed by the incoming cool oil. The cooling solution is presented in more details in [22].…”

“…where r is the radius measured from the rotor centre-line to the middle of the air gap, S r is the rotor surface area facing the air gap, v is the linear speed of the rotor surface, is the rotor angular velocity, δ is the air gap length and µ is the dynamic viscosity of hydraulic oil [22]. In the proposed drive system, air gap is only partly filled with oil and therefore an appropriate share of this value will be the practical result.…”

Oil Friction Loss Evaluation of Oil-Immersed Cooling In-Wheel Motor Based on Improved Analytical Method and VOF Model

“…At present, there are some reports about the oil friction loss of an oil-immersed cooling motor, most of those are the analytical method. Montonen [12] presented thermal analyses of a partial oil-immersed cooling Permanent Magnet Synchronous Motor (PMSM). The error of oil friction loss between the calculation using the formulas derived from the gear pair power loss model [13] and measurement was nearly 50%.…”