![]() ![]() ![]() Smoother operation results from the out-of-phase force generated by the start winding. The motor could easily operate on the run winding alone however, it will run more smoothly and efficiently when the start winding and capacitor remain in the circuit. Often found in direct drive furnace fan applications and in hermetic compressors, the PSC motor has no centrifugal switch to take the start winding out of the circuit. Undoubtedly, the workhorse motor of the residential HVAC industry to this day is the permanent split capacitor motor (PSC). The stator core has a pair of permanently short circuited (shading) coils placed over a portion of the main field coil causing an unbalance of magnetic forces so that the motor is self-starting (see Figure 1). Once the rotor achieved approximately 75 per cent of running speed, a centrifugal switch would open and take the start winding out of the circuit.Īnother single phase motor commonly used throughout the industry in low torque starting applications is the shaded pole motor. The rotor had no windings, but magnetism built-up around the rotor bars. Thus, the two windings together created a rotating field causing the rotor to revolve. Wired in parallel, the auxiliary winding would, during start-up, produce a magnetic field out of phase with the magnetic field produced by the main winding. The motor had two windings, the main winding and the high resistance auxiliary winding rotated several degrees in magnetic position from the main winding. The 115-volt split phase AC motor found a home in many belt-driven low starting torque applications (like fossil-fueled furnace fans) long before I ever set foot on the scene. Residential installers and technicians typically encounter single phase induction motors classified by the method used to start them: Miscellaneous drives: deep vacuum pumps, recovery machines, ice makers, EEV stepper motors, among others.īefore the advent of electronically controlled motors, there were two general classes used to identify electric motors: single phase induction motors and three phase induction motors. Pump drives: condensate pumps, hydronic system pumps, chilled water pumps, geothermal system pumps, and cooling towers. HVAC runs on electric motors, which are used in several general classifications:Ĭompressor drives: hermetic direct drive and external driveįan drives: condensers, evaporators, induced draft, air circulation Indeed, today’s global market for electric motors is close to 100 billion US dollars and is expected to grow to 141 billion by 2022 according to Sherry James of Grand View Research. Years later in 1883, Nicola Tesla invented the first induction motor with rotating magnetic fields thus starting a second industrial revolution still evident today. Faraday had converted chemical energy from a battery into mechanical motion creating the threshold to our world in motion. The great British scientist, Michael Faraday, experimented with electricity and magnetism and, in 1821, he set in motion a copper conductor rotating around a magnet sitting in a bath of mercury. By the time the refrigerator, vacuum cleaner, washer/drier, range hood, outdoor unit, submersible pump, and several other devices are counted, I am employing north of 25 motors nearly every day. Even at home, the ubiquitous electric motor is indispensable.Īs I sat down to write this article, I performed a quick mental survey of the electric motors just in my basement: furnace (three motors, including condensate pump) HRV (three motors) upright freezer (one motor) sump pump ( one motor) propane stove (one motor) desktop computer (one motor) printer (one motor). Whether designing new products, specifying equipment, installing, maintaining or repairing a variety of heating, ventilation or cooling products, an electric motor and its needs are regularly the centre of attention. Everyone involved in HVAC and refrigeration works with electric motors almost every day. ![]()
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