Operator Interfaces, Switches & Relays


Supply voltage influences and damage control

August 2015 Operator Interfaces, Switches & Relays

It is often wise to include supply voltage monitoring as a useful tool for prolonging motor life expectancy and possible mechanical damage to equipment due to, for example, motors turning in the wrong direction as a result of voltage phase rotation. Essentially, the protection given falls into three categories: the detection of an over-voltage condition; the detection of an under-voltage condition; and the detection of voltage phase rotation on the supply side.

High voltage on a motor tends to push the magnetic portion of the motor into saturation. This causes the motor to draw excessive current in an effort to magnetise the iron beyond the point where magnetising is practical. Low voltage can lead to overheating, shortened life, reduced starting ability, and reduced pull-up and pull-out torque. When the supply voltage is reversed, the connected motor will rotate in the opposite direction and will almost always result in some or other form of mechanical damage.

In conclusion, no stress should be placed on electric motors and other electrical equipment as a result of operating a power system at or near the ends of voltage limits. The best life and most efficient operation usually arise when motors operate at voltages very close to the nameplate ratings.

NewElec offers a variety of products that include protection for supply ­voltage influence.

For more information contact NewElec, 086 010 3041, [email protected], www.newelec.co.za



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