A Website on Maintenance of Electrical Systems

The electrical grounding system is a backup path for electric current to flow back to the power source in case of a fault. Nature Of Electric Current Flow. Electric Current flows from a power source through live wires to a load. The current then returns  back to the power source  through the neutral wire. The same is true for AC and DC power sources. current always returns to the power source. It is important to know that electric current always tends to flow through the path of lowest resistance. Power sources include 1) Batteries - electrons flow from negative to load returns through positive. 2) Transformers - current flows from phase to load returns through neutral. 3) Alternators  - current flows from phase to load returns through neutral. Short Circuit  A complete and healthy circuit loop is formed when electric current flows from the source, to the load and back to the source through the neutral. This is the normal path in which electricity is expected to

A Relay is an electrically operated switch, it basically consists of an electromagnetic coil which builds up a magnetic field when current is passed through it. This magnetic field is used to operate the relay contacts to an OFF or ON state. A Contactor is an electrically operated switch, it basically consists of an electromagnetic coil which builds up a magnetic field when current is passed through it. This magnetic field is used to move the contactor contacts into an OFF or ON state. So what is the difference between a relay and a contactor. In the most simplistic terms, a contactor is a  relay  is used to switch a large amount of electrical power through its contacts . Other notable differences are stated below. 1)     Relays tend to be for logic switching while contactors are for Power switching 2)     Relays don’t come with auxiliary contacts while many contactors have provision for auxiliary contacts 3)     Relays are commonly used for single phase applicati

Mercury Vapor lamp is one of many kinds of electric lamps designed to produce light from electricity. Other types of electric lamps available in the marled include the Incandescent bulb, LED bulb, Florescent, sodium Vapor, and Metal Halide. Electric lamps could be broadly divided into two categories. 1)     Incandescent 2)    Gaseous Discharge Lamp. Gaseous discharge lamps could be further divided into High pressure and low-pressure gaseous discharge lamps. Mercury Vapor lamps fall under the Gaseous discharge lamp category. Other lamps in this category are Metal halide and high and low-pressure sodium lamp and fluorescent lamp. All gaseous discharge lamps generate light using the same principle i.e. passing an electrical arc through a gas. Mercury Vapor lamps fall under the High-Pressure Gaseous Discharge lamp category. They are also commonly referred to as High Intensity Discharge (HID) lamps. Metal Halide and High-pressure Sodium (HPS) lamps are also called HID lamps. Al

NEMA frame size refers to the physical dimensions and mounting of the electric motor.  They are a key part of motor interchangeability; in essence, a motor from one manufacturer can be replaced with a similar motor from another company provided they are both of the same frame size. The shaft length, shaft diameter, mounting foot dimensions, distance from the center of the shaft to the bottom center of the mounting foot are all part of the frame size standard. The physical dimensions of an electric motor have also been standardized by NEMA where “D” dimensions refers to the distance from center of shaft to bottom center of mounting foot, “U” dimensions refers to the diameter of the shaft, “N-W” dimensions refers to the length of the shaft, “F” dimensions refers to the distance from the center of the mounting foot to the center of base mounting hole in the side view and so on and so forth. A standard Frame size designation for electric motors is either made up of either 2 or 3

Single phasing fault is the worst case of voltage imbalance in a three-phase supply where there is a break on one of the phases in a 3- phase supply hence the remaining phases draw excess current w hich quickly overheats the motor windings and reduces the power output of the motor drastically. Causes Of voltage imbalance and single phasing on an induction motor. 1) Faulty Circuit breaker – This is a situation where there is an open pole in the circuit breaker and that phase becomes absent. 2) Blown fuse – One of the three fuses use for protection if the circuit melts and supply is current is lost on that phase. 3) Faulty contactor- One of the phases of a contactor could be damaged or coated due to rust and not conducting. 4)  Partial Contact – also known as high resistance connection. A  l oose connection  anywhere on the power circuit could create a very high resistance joint which will cause  a severe  voltage  drop at that point. This could cause complete loss of voltag

The nameplate of a power transformer contains the following details as per standard, then additional information could be provided varying from manufacturer to manufacturer. Name Of Manufacturer Serial Number Year Of Manufacture Connection Symbol – This tells you the HV winding and LV winding configuration of a transformer and difference in phase angle between them. Example DYN11 where the first letter represents the HV winding and indicates that it is connected in delta, the second letter represents the LV winding and indicates that it is connected in Star(wye)  and the third letter N indicates that the LV winding has a Neutral while 11 denotes a 30 degree lead in phase angle. This article explains more on the Vector group of a transformer and why it is important.  (Transformers connected in parallel must have the same vector group i.e. same phase angle shift to avoid circulating currents. This is a situation where one source will become load to the other sourc