Month: September 2013

The Phase Monitor

  In recent years, it has become difficult for some power companies to maintain the level of power required to run HVACR equipment during periods of very hot weather. When the voltage drops below 10% of the rated line, a  so-called “brownout” occurs, resulting in a voltage/phase imbalance. Sometimes there is a complete phase loss. …

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Run Capacitors for HVACR

  Almost all run capacitors use oil and paper as the dielectrics. Because of the hazards involved with oil, a system of protection was devised to prevent fires from occurring within the equipment. The figure on the right shows how a fusing device is incorporated into the capacitor. This safety feature is designed to prevent an explosion or …

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Motor RPM Calculation

  The speed of a fractional-horsepower motor is determined by the number of poles the motor has and the frequency of the current supplied to it. This equation is used to determine the synchronous speed of an ac motor: where “f” is the frequency (cycles per second) of the power supply, and p is the …

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