What happens to electric motors when they are supplied with high voltage levels?
Motors are particularly susceptible to over-voltage. While it depends where they are manufactured, the majority of 3-phase motors in Australia are designed to operate optimally at 380-390V. The average supply voltage in Australia is significantly higher than this (approximately 415V). Some of the problems this excess voltage creates for 3-phase motors include; • Internal energy losses (iron and copper losses in the form of heat) • The iron core becomes saturated as the motor draws excess current. The core is magentised beyond its optimal and designed rated capacity and the iron loss is proportional to the square of the voltage increase. • Additional internal losses as a result of the reversing magnetic field passing through the iron core. • Extra strain upon the motor (heat, vibration etc.) reduces its life span and increases maintenance requirements.
