Up until this point we have been talking about basic control elements (switches, contactors, relays, and thermostats) as well as transformers (which are both loads and supplies). Now we are going to start talking about motors, the real workhorse of the HVACR trade as well as many other industries.
Motors are electro-mechanical components that take electrical current (power) and create motion and force. Motion is the rotation or linear movement; force is the amount of work that is accomplished by this movement.
There are several types of motors that we are going to talk about, each of these motor types has its own place in the HVACR industry. These motor types are:
- Shaded Pole
- Split Phase
- Permanent Split Capacitor (PSC)
- Capacitor Start Induction Run (CSR)
- Capacitor Start Capacitor Run (CSCR)
- Electronically Commuted Motor (ECM)
- Three Phase Motors
- Heat Motor
The list above starts with the simplest, lowest torque motors and moves towards the heaviest. The exception is the heat motor, which we will talk about near the end of this section.
Parts of a Motor
The typical Alternating Current (AC) motor includes the motor frame which holds all components together, the stator, the rotor, the shaft, the bearings, and the wiring connections.
The rotor is attached to the shaft. The stator is attached to the motor frame and is where the motor windings are attached. The rotor rotates inside the stator when power is applied to the motor.
The windings are coils of wire. When you apply current to a winding, just as in the transformer, it creates a magnetic field. Any magnetic field has poles, North and South. As we discussed earlier alternating current reverses polarity 60 times a second (in the US) and 50 times per second (in Europe). When this current reverse polarity the magnetic field reverses as well. So, 60 times per second North becomes South, and South becomes North.
The rotor is made up of permanent magnets. There are a number of magnets mounted around the rotor, parallel to the shaft. Each magnet has a North and a South pole. Magnetic poles either attract or repel each other.
Like poles repel each other. Unlike poles attract each other.
The stator (windings) of the motor changes polarity 60 times a second. The rotor is surrounded by magnets each having a permanent North and South poles. Because of the constructor of the windings on the stator, and the magnets on the rotor, once current is applied to the motor the shaft rotates as the magnets are repelling each other with the shifting of the magnetic field.
The motor uses this rotation to do work.