Abstract
Thermal overload relays are economic electromechanical protection devices which offers reliable protection for electric motors in the event of overload or phase failure. Presently there are two types of overload relays which depend on the temperature characteristics of metals to provide protection by tripping the circuit. These relays lack accuracy as they do not activate the trip circuit at any exact specified temperature. In this paper we introduce a new form of thermal over-load relay actuated by ferrofluid. The ferrofluid has a very accurate transition temperature known as curie temperature. It acts as a ferromagnetic material below the curie temperature and loses the property of ferromagnetism above this temperature. By using this property of the fluid we propose an alternative method for more accurate op-eration under overload condition. This relay finds application in the protection system of electrical machines. Thus, in this paper we present a novel and simple technique for protection against thermal overloading using ferrofluid.
Highlights
A relay is an electrically operated switch which is used to control a circuit by a low-power signal with complete electrical isolation between control and controlled circuits
In this paper we introduce a new form of thermal overload relay actuated by ferrofluid
In this paper a new type of thermal overload relay is recommended which provides an accurate tripping of the circuit preventing the overheating of the motor
Summary
A relay is an electrically operated switch which is used to control a circuit by a low-power signal with complete electrical isolation between control and controlled circuits. Thermal overload relays are designed to cut the power by opening the circuit when the motor draws too much current from the supply for an extended time causing temperature rise. There are two types of thermal overload relays (Figure 1) in which one type has a bi-metallic strip [1] which deflects as the temperature rises until it causes the device to trip and open the circuit. The main motive of our technique is to isolate the machine and to protect them from damage during the event of thermal overload. This relay has a better accuracy and shuts the power down at a specific temperature
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