circuit protection should operate in the event of a fault to earth. The speed of operation of the protective device is of extreme importance and will depend on the impedance of the earth fault loop path. • the circuit protective conductor (CPC)• the consumer’s earthling terminal and earthing conductor• the return path, either metallic or …
The thin layer of material which covers our planet – rock, clay, chalk or whatever – is what we in the world of electricity refer to as earth. So, why do we need to connect anything to it? After all, it is not as if earth is a good conductor It might be wise at …
This is the passage of current through the body of such magnitude as to have significant harmful effects. below Figure illustrates the generally accepted effects of current passing through the human body. How, then, are we at risk of electric shock and how do we protect against it? 1 mA–2 mA Barely perceptible, no harmful …
The basic analog multimeter is commonly referred to as a VOM (volt-ohmmilliammeter). The VOM shown measures ac and dc volts from 250 mV full scale to 1000 V, dc from 50 μA full scale to 10 A, ohms up to 20 M, and decibels (dB) with a total of 29 ranges. The accuracy on dc …
The batteries used in most industrial situations (other than standby emergency use) are used in what is called cyclic operation. That is, the battery is either being charged or being used (discharged). In most such applications batteries are charged about 1500 to 2000 times during their lives. Incorrect charging for a few cycles will do …
Two types of lead-acid batteries are manufactured for industrial applications. These are generally referred to as motive-power and stationary batteries. Typical applications for motive-power batteries include material-handling trucks, mine locomotives, mine tractors, mine shuttle cars, floor sweepers and scrubbers, heavy-duty personnel carriers, transport vehicles, golf carts, and lawnmowers. Typical applications for stationary batteries are switchgear …
The following troubleshooting flowcharts should provide logical, step-by-step methods for determining solutions to motor problems. They should be used as a guideline by qualified competent personnel. Troubleshooting ac Motors A. Motor won’t start or accelerates too slowly.B. Motor runs noisy.C. Motor overheats.D. Motor bearings run hot or noisy. Troubleshooting dc Motors E. Motor won’t start.F. …
Maintenance Plan. A specific maintenance plan that is carried out on a regular basis is a primary factor in preventing motor problems and failures. And, when problems do arise and system shutdown is inevitable, a logical, step-by-step method of troubleshooting can save time and money. At the very least, the motor manufacturer’s maintenance schedule should …
Theory and Construction. Induction motors are common in most industrial applications. They all have primaries, or stator windings, connected to a power source, with a secondary winding, or rotor, which drives the mechanical load. The most common type of induction motor is the squirrel-cage motor, so named because its rotor construction entails bars of copper …
No-load operation The basic operation of all these generator types can be explained using two simple rules, the first for magnetic circuits and the second for the voltage induced in a conductor when subjected to a varying magnetic field.