March 2014

In any medium or low voltage three-phase system there are three single-phase voltages which are measured between each phase and a common point called the “neutral point”. In balanced operating conditions these three voltages are phase shifted by 120° and have the value: U being the phase-to-phase voltage measured between phases (see fig). From a […]

Solidly grounded systems are usually used in low voltage applications at 600 volts or less. In solidly grounded system, the neutral point is connected to earth. Solidly Neutral Grounding slightly reduces the problem of transient over voltages found on the ungrounded system and provided path for the ground fault current is in the range of

In un-grounded system there is no internal connection between the conductors and earth. However, as system, a capacitive coupling exists between the system conductors and the adjacent grounded surfaces. Consequently, the “ungrounded system” is, in reality, a “capacitive grounded system” by virtue of the distributed capacitance. Under normal operating conditions, this distributed capacitance causes no

There are many neutral grounding options available for both Low and Medium voltage power systems. The neutral points of transformers, generators and rotating machinery to the earth ground network provides a reference point of zero volts. This protective measure offers many advantages over an ungrounded system, like: · Reduced magnitude of transient over voltages ·

There are many topologies of electric machines, which create various classifications. Traditionally, they were classified into two groups DC and AC. With the advent of new machine types, this classification becomes ill-suited. Figure 3 shows the proposed classification of electric machines in which the bold types are those that have been applied to renewable power

An overview of renewable energy sources, including the wind, wave, hydro, tidal, solar-thermal, geothermal and biomass-thermal, which utilize electric machines for electricity generation is presented; whereas the solar electric (photo voltaic) and thermoelectric power generations which directly produce electricity without using electric machines will not be discussed. Basically, these renewable energy sources can be categorized

As their name implies, motor starters apply electric power to a motor to begin its operation. They also remove power to stop the motor. Beyond merely switching power on and off, starters include overload protection, as required by the National Electrical Code. The code also usually requires a disconnect and short circuit protection on motor

Rigid base is bolted, welded, or cast on main frame and allows motor to be rigidly mounted on equipment. Resilient base has isolation or resilient rings between motor mounting hubs and base to absorb vibrations and noise. A conductor is imbedded in the ring to complete the circuit for grounding purposes. NEMA C face mount

A brake motor is a pre-connected package of industrial-duty motor and fail safe, stop-and-hold spring-set brake. In case of power failure, the brake sets, holding the load in position. Brake motors are commonly used on hoists or other lifting devices. Brake features can also be added to standard motors through conversion kits that attach to

These motors are always part of integrated motor-and-controller systems that provide extreme accuracy in positioning and speed. Common applications include computer-controlled manufacturing machines and process equipment. Servomotors are the largest category of motors for precision motion control. AC, DC brush-type, and brushless DC versions are available. Closed-loop control systems, common with servomotors, use feedback devices