LIMITATIONS IN ELECTRICAL MACHINE DESIGN
We have the availability of suitable materials and facilities to create an electrical machine including transportation, the following are the limitation on designing of the electrical machines
- Temperature Rise
- Mechanical Parts
- Power Factor
- Consumer Specifications
- Standard Specifications
In the designing of the electromagnetic machines we use ferromagnetic material. The flux density of the machine is determined by the saturation of the ferromagnetic material used. Higher flux density results in higher cost.
The most important part of the machine is the insulation. It should be according to the maximum temperature in the machine. If the operating temperature is higher than the allowable temperature its life will be drastically reduced. Proper ventilation techniques are used to keep the temperature rise in the safer limits. The coolant will allow the heat from the machine to dissipate.
The insulation is the most important part as it should with stand the electrical mechanical and thermal stress produced by the machine. Transformers are the machines which should have higher insulation where the large axial and radial forces are produced when the secondary winding of the transformer is short-circuited with primary on. It should withstand high mechanical stress due to secondary winding is short circuited.
Efficiency should be high to reduce the operation cost of the machine. So it requires large amount of materials to design. We can reduce the operating cost by increasing the design cost.
The construction of the mechanical parts should be economical but it should satisfy the requirements of performance, reliability, and durability. For the high speed machines it is very important because it will be having more mechanical stress at the rotor. The length of the airgap is reduced to increase the high power factor.
This problem only occurs in the commutator machines. As it decreases the maximum output taken from the machine.
Poor power factor results in large amount of current in the same power, therefore large conductor sizes have to be used. It mostly affects the induction motor.
The important in this is it should satisfy the consumer specification with their economic constrains. The design should evolve in this manner.
This specification cannot be neglected by both consumer and manufacturer. So this becomes the biggest constrain.