EDU (Electric Drive Unit) Cooling & Lubrication
Vibin Jacob
18y exp in R&D Product Dev.,Thermal System(HVAC and Powertrain cooling), NVH, Vehicle Development,Testing & EV thermal.
Thermal and mechanical loads in motor can cause a number of undesired effects due to trends aiming to increase power densities and maximum speeds.
Approach often aims towards?removing as much heat from the system as efficiently as possible with motor, bearing and spindle shaft cooling.
A cooling sleeve is provided at shaft bearing, spindle motor and hollow shaft to reduce operating temperature by bearing friction as well as motor losses.
The coolant temperature for the electric motor, battery, and power electronics is maintained at?below 60°C?inside a separate cooling circuit using a low-temperature radiator.
Normal operating temperature for?bearings?in an electric?motor?range from 70 to 110 °C.?
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Thermal management of electric vehicles (EVs) with high power density requires direct cooling strategies in which the cooling fluid is in direct contact with the hot spots of the electric motor. In a EV Motor rotor magnets generate a certain amount of heat that cannot be properly cooled down by a conventional water jacket cooling. Hence the development of direct oil cooling technology in which the transmission oil is used as a coolant for the electric motor. This cooling architecture generally implements a hollow rotor shaft where transmission oil flows, holes located at both ends of the rotor shaft allow the oil to be splashed on the end windings with centrifugal force. The direct oil cooling system significantly improves heat transfer.
This shift oil cooling is not motivated by the fact that a oil has superior cooling properties than a water-based coolant. On the contrary, water is often an ideal cooling fluid due to its high thermal conductivity, high heat capacity, and low viscosity. However water application is unfeasible since the cooling fluid directly interacts with electrical components, where high electric currents and voltages occur (require low electrical conductivity). Secondly, the fluid comes in direct contact with gears and bearings and required to have lubricating qualities.
18y exp in R&D Product Dev.,Thermal System(HVAC and Powertrain cooling), NVH, Vehicle Development,Testing & EV thermal.
1 年Magnetomotive force (mmf),?Fm?= N x I ampere-turns (At), where N = number of conductors (or turns) and I = current in amperes. Since 'turns' has no units, the SI unit of mmf is the ampere.?The electric field E, current density J and conductivity σ of a conductor are related as?J = E ρ.?The number of field turns per pole multiplied by the current in the winding equals the total mmf. The current density in the copper determines the total loss to be dissipated and hence the temperature of the winding. For constant current density, as the designer would change the number of turns, the copper area per turn and hence the current per turn would be changed inversely, but the total mmf per pole would remain unchanged. Since field-winding voltage is proportional to the number of turns, its selection does not affect the mmf available.A major determiner of the mmf capability of the field winding is the temperature of the conductors. Increasing this capability may be done through (1) insulation capable of higher temperature, (2) more effective cooling systems, and (3) methods of increasing total area in the rotor cross section, available for copper. In large machines, higher temperature may cause increased thermal stresses in the field-winding conductors, which must be accomodated. Careful attention to many important details is essential to the successful design of a field winding.