A Website on Maintenance of Electrical Systems

  A Magnetic Overload relay works by detecting the magnetic field strength generated by the current flowing to the motor.  In most cases the relay input is a representation of the  current (through C.Ts)  flowing into the motor.   The Magnetic Overload Relay is built in such a way that the magnetic flux set up by current flowing through the  coil  drags (pulls) the core upward. A typical dashpot type magnetic overload relay is shown in the image below.                                    Construction. The relay consists of two main parts which is the trip mechanism at the top and the dashpot at the bottom.  The parts of the relay are further divided into a coil, a plunger (core), an oil-filled dashpot and switching contacts (trip contacts). The plunger is attached to a piston (disc). The piston is suspended in an oil filled chamber.  The relay coil is connected in series with the motor supply circuit. During normal operation magnetic flux induced by the coil is not great enough to c

  Leading power factor means that the current leads the voltage.  In other words, the load is capacitive.  If the real power load is 10kW at unity power factor, the kVA is 10kVA.  If the real load power is 10kW at  0.95 power factor (Leading Or Lagging),  kVA is 10.52kVA. The effect of leading power factor on the network are as follows 1) More current would flow in the circuit, this current could go above the cable ratings and higher current means bigger cables. S = VA Where: S =  10.52kVA =  10520VA V = 415 A  =? 10520 = 415 x A A = S/V = 25.35A in the circuit instead of 24.1A at unity PF 2)  Leading power factor will boost the output voltage of the supply generator. This happens due to over excitation of generators. (Leading PF causes high voltage in the circuit)  When Electrical devices equipment's are supplied with a voltage higher that its rated voltage, equipment damage/failure would most certainly occur. 

 What is a Neutral Link? Neutral links are metallic bars that are usually constructed of copper, aluminum or brass and act as an  electrical terminal in an electrical circuit . Below is an image of a neutral link.   The neutral link serves as termination point of the neutral of all individual circuits. The Neutral serves circuit return path or path completion line. Current that flows to the load returns trough the neutral, now since the neutral link is a neutral point for various circuits, it is designed to withstand a high amperage. Back to the question  why link is provided in neutral of an AC circuit and fuse in phase of AC circuit? Suppose there is no neutral link and a fuse is put on the live line and also in the neutral of a single-phase circuit.   In the event of a phase to neutral fault, very high current would flow in the circuit on both live line and neutral and the fuse would blow. Both wires are fused in so  you can't tell for sure which fuse will blow off w