Home Packup Generator

electric generator service is one of the most comprehensive in the business—because we know the importance of staying connected and staying safe when the power goes out. Whether we’re installing a new generator or servicing a backup generator, we’ll assess your needs and make sure that you have peace of mind.
WHAT IS A GENERATOR?

Generators are standby devices which can supply electricity to your home during power outages. During a power outage, it allows you to continue to operate essential appliances such as refrigerators, computers, heating and cooling systems and lighting.

The process that generators employ involves converting mechanical energy into electric energy. This is the same process that is used, on a larger scale, to produce electricity for entire communities by your local utility provider. In essence, a spinning shaft powered by an engine is used to produce a magnetic field through a coil, which in turn produces an electromotive force.
CHOOSING A GENERATOR

Home generators can be either portable or stationary. They run on a variety of fuels including, gasoline, diesel, natural gas, propane and oil. Generally, gasoline portable models are less expensive to purchase. However, they typically have shorter run times because of the need to refill the tank, if used constantly. And if the outage is due to wide spread outages or severe weather conditions, gas pumps may not be operational. Natural gas with its constantly available supply, tend to be the more reliable for stationary models.

The main differences between stationary and portable models are in their connection and activation. A portable unit has to be moved to your location, filled with fuel and then connected to fuel line, manually started then connected to your load requirement. Portable units allow for easy storage when needed. A stationary unit can start immediately and is usually already wired to the home and the fuel source. A determining factor as to which works best involves how much space you have for the unit, since a stationary unit may require a concrete pad.

Generators usually come in sizes that range from an output of 1 kilowatt (kw) to over 100 kw.
CHOOSING A FUEL TYPE
Your choice of fuel should be determined by the fuels available in your area. The more remote your location is, the bigger the concern for having available fuel will be. As mentioned earlier, gasoline, diesel, fuel oil and to an extent propane, have limited availability and delivery in extreme circumstances. Natural gas can also be limiting if you are not connected to their distribution system.
WIRED SYSTEMS

A standby power backup device connects to the house wiring through a transfer switch. The transfer switch prevents ‘backfeeding’ into utility lines, which is dangerous and illegal. It also protects the device from damage caused by the utility company applying voltage to your house wiring while it is operating. These switches can either be automatic or manual and should be rated to carry the larger of the maximum load of the residence or the full output of the generator.
LIMITATIONS

If your generator is intended to supply only a portion of your home's electrical load, a list should be made of the electrical equipment to be powered during an outage, for example; appliances, lamps, furnace blower motor and the like. Compare the total wattage of the equipment to the total wattage output rating of the generator and do not exceed it.

In any case of installing stationary generators, or performing electric generator service, a licensed Mister Sparky® electrician should perform all the electrical connections to avoid any problems. Additionally, all wiring and equipment must comply with local, state and federal laws or codes, inspected and adhere to the rules and regulations of your local utility.



Posted via A.Mohamed Nazar

DC Motor

DC motors

A simple DC motor has a coil of wire that can rotate in a magnetic field. The current in the coil is supplied via two brushes that make moving contact with a split ring. The coil lies in a steady magnetic field. The forces exerted on the current-carrying wires create a torque on the coil.

The force F on a wire of length L carrying a current i in a magnetic field B is iLB times the sine of the angle between B and i, which would be 90° if the field were uniformly vertical. The direction of F comes from the right hand rule*, as shown here. The two forces shown here are equal and opposite, but they are displaced vertically, so they exert a torque. (The forces on the other two sides of the coil act along the same line and so exert no torque.)
* A number of different nmemonics are used to remember the direction of the force. Some use the right hand, some the left. For students who know vector multiplication, it is easy to use the Lorentz force directly: F = q v X B , whence F = i dL X B . That is the origin of the diagram shown here.
The coil can also be considered as a magnetic dipole, or a little electromagnet, as indicated by the arrow SN: curl the fingers of your right hand in the direction of the current, and your thumb is the North pole. In the sketch at right, the electromagnet formed by the coil of the rotor is represented as a permanent magnet, and the same torque (North attracts South) is seen to be that acting to align the central magnet.
Throughout, we use blue for the North pole and red for the South. This is just a convention to make the orientation clear: there is no difference in the material at either end of the magnet, and they are usually not painted a different colour.
Note the effect of the brushes on the split ring. When the plane of the rotating coil reaches horizontal, the brushes will break contact (not much is lost, because this is the point of zero torque anyway – the forces act inwards). The angular momentum of the coil carries it past this break point and the current then flows in the opposite direction, which reverses the magnetic dipole. So, after passing the break point, the rotor continues to turn anticlockwise and starts to align in the opposite direction. In the following text, I shall largely use the 'torque on a magnet' picture, but be aware that the use of brushes or of AC current can cause the poles of the electromagnet in question to swap position when the current changes direction.

The torque generated over a cycle varies with the vertical separation of the two forces. It therefore depends on the sine of the angle between the axis of the coil and field. However, because of the split ring, it is always in the same sense. The animation below shows its variation in time, and you can stop it at any stage and check the direction by applying the right hand rule.