Energy efficient motor from advanced system design and part selection

Motor efficiency is a key design parameter and the efficiency of motor design is more important than ever.

Energy-efficient motors are made of high-quality materials and optimized designs for greater efficiency. For example, the higher the aluminum content in the rotor, the higher the groove fill factor in the stator and the lower the resistance loss. The optimized rotor structure and rotor-stator air gap reduce stray load losses. The improved cooling fan design minimizes the windage loss of the motor cooling, and the higher quality and thinner steel laminations for the rotor and stator cores greatly reduce magnetization losses. Finally, reducing friction losses is caused by higher quality bearings. The figure below shows the anatomical view of the AC induction motor, illustrating the housing and bearing components.

Optimize the size of the rotor/stator lamination and the quality of the steel used

The hysteresis loss and eddy current loss are collectively referred to as core loss, and about 20% of the total loss is caused by eddy current and core saturation. The eddy currents generated in the laminations move relative to the changing magnetic field, resulting in significant power loss. The laminated stator core reduces eddy current losses and, based on the mass, resistivity, density, thickness, frequency and flux density of the iron, eddy current losses can be minimized by more laminations.

Hysteresis loss is the result of a magnetic circuit that changes as the magnetic flux changes. Most of the load material used in the motor is steel for the stator and rotor cores, which minimizes the flux density and core loss by reducing the laminate thickness. The hysteresis loss can be reduced by annealing a better grade of lamination steel to change the grain structure to facilitate magnetization. The eddy current loss is reduced by increasing the resistivity of the silicon-containing steel, but the silicon content increases the mold wear during the stamping process because it increases the hardness of the steel. Damaged steel crystals during stamping severely degrade the magnetic mass of the affected volume. Annealing flattens the laminate and recrystallizes the damaged crystal during the stamping process, thereby extending the thickness of one sheet into the laminate.

Stator lamination using a bath process

The impregnated stator enhances the electrical insulation of the stator windings to prevent chemical or harsh environmental effects and enhance heat dissipation. Thermoset plastics include epoxy, phenolic, and polyester for impregnating the stator. The bathing method is to immerse the stator in the resin for a longer period of time to ensure optimum penetration and protection. Another method of impregnation is called vacuum pressure, which uses a tank that is first evacuated and then pressurized to achieve penetration into the stator. Finally, the extraction of air pockets from the electrical windings improves the thermal conductivity of the windings.

Design slots in the stator to maximize the volume of copper that can be inserted

The slot full rate will affect the stator winding to a low level, which will result in 60% of the total loss. Therefore, in order to reduce the total loss, the quality of the stator winding must be large, thus reducing the resistance. Compared to standard efficiency motors, high efficiency motors contain more than 20% extra copper, and the stator's insulated windings are placed in the slots of the steel sheet. The cross-sectional area must be large enough to meet the rated power of the motor. In general, induction motors use open or semi-closed stator slots. In a semi-closed groove, the opening of the groove is much smaller than the width of the groove, and the winding is more difficult and time consuming to manufacture than the open groove. The number of stator slots must be selected during the design phase as this affects weight, cost and operating characteristics. The advantages of multi-slots are reduced leakage resistance, reduced tooth pulsation loss, and improved overload capability. The disadvantages of more stator slots are increased cost, increased weight, increased magnetizing current, increased iron loss, poor cooling, increased temperature rise, and reduced efficiency.

Rotor die casting is made of high quality pure aluminum

Custom designed rotors maximize starting torque, reduce conductor resistance and increase efficiency. Most induction motor rotors are designed in a squirrel cage. They are rugged, simple in construction and low in price, but they have low starting torque. Copper rotors increase efficiency but are difficult and expensive to manufacture.

The air gap between the rotor and the stator is optimal

The air gap is the radial distance between the rotor and stator of the motor in a standard radial motor. In order to improve design efficiency, it is necessary to maintain an optimum air gap. Air gap dimensions relate to the design of the stator, rotor, motor housing and bearings. All of this affects the precise alignment of the stator and rotor shafts.

Enameled wire

The magnet or enameled wire is an electrolytically refined copper or aluminum wire that has been fully annealed and coated with one or more layers of insulation. For example, a wire having a total of 12 insulating layers is used. Typical insulating films, with increasing temperature range, are available in polyethylene, polyurethane, polyester and polyimide with temperatures up to 250 °C. Thicker rectangular or square magnet wires are wrapped with high temperature polyimide or fiberglass tape, using more copper, and larger conductor bars and conductors increase the cross-sectional area of the stator and rotor windings. This reduces the resistance of the windings and reduces the losses caused by the current, which typically results in 20% more copper in the stator windings of high efficiency motors.

Reprinted from the network