## Motor Equations

The following equations are useful in determining the current, voltage, horsepower, torque, and power factors for three phase AC motors;

E = volts (line-to-line) 1 = current (amps) PF = power factor r\ - efficiency hp = horsepower kW = kilowatts kVA = kilovoltamperes N = speed, rpm T = torque, ft-lb

A typical medium-size, squirrel-cage motor is designed to operate at 2-3% slip (97-98% of synchronous speed). Synchronous speed is determined by the power system frequency and the stator winding configuration. If the stator is wound to produce one north and one south magnetic pole, it is a two-pole motor. There is always an even number of poles (two, four, six, eight, etc.). The synchronous speed is

where

P - number of poles

The actual operating speed will be slightly less by the amount of slip. Slip varies with motor size, load, and application. Typically, the larger and more efficient the motor, the less full-load slip. A standard 10-hp motor may have 2XA% slip; whereas, motors over 1,000 hp may have less than XA% slip. Operating slip can be approximated by multiplying % load by full-load slip.

## Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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