Insulation is done for preventing the wire current from coming into contact with other conductors. It will protect the current carrying wire from environmental threats and electrical leakage. The insulated material is mainly resistant to electrical current Insulating material in electrical machines is grouped into several classes
Class A is organic materials like linen and cotton Class B is an inorganic example mica glass…
While doing the design of an electrical system if the size of the insulation increased then the available space of the conductor which carries current will be less
REQUIREMENTS OF AN INSULATION SYSTEM FOR MACHINE WINDING • Better thermal conductivity • Dielectric strength • Resistance to abrasions • Resistance to moisture and oil vapor • Resistance to partial discharges • Resistance to tape separation which is caused by thermal heating
If the machine is operated above permitted temperature the insulation life will be shortened so the machine should operate under the permitted temperature
Many insulation failures are caused by moisture oil and dirt so we must do the inspection of insulation at regular times.
MACHINE INSULATION IS DONE BY FIVE MAJOR INSULATION SUBSYSTEMS
• Turn to turn insulation system – it is between separate wires in each coil it is usually in the form of enamel coating on the wire
• Phase to phase – this type of insulation is done between adjacent coils which are in different phase group
• Slot wedge insulation system – this type will hold the conductor firmly in the slot
• Impregnation insulation system – this will provide protection against contaminants this will bind all the other components together and to fill the air space
• Phase to ground insulation system – this is located between the windings as well as between the windings and ground part of the motor a sheet material will provide dielectric and mechanical protection