Motors - How to Choose an Electric Motor
How to Choose an Electric Motor
Simply put, an electric motor converts electrical energy into mechanical energy. This is achieved by the principle of electromagnetic induction. Electromagnetic induction is the principle that a current carrying conductor, when placed in a magnetic field will have a force exerted on the conductor proportional to the current flowing and the strength of the magnetic field. The basic principles of electromagnetic induction were discovered in the early 1800's by Oersted, Gauss and Faraday. However, it was Tesla who was able to take motor technology to the next level in the late 1800's and revamped the manufacture of motors as well. Tesla was able to successfully garner 900 patents in the
electrical field that had relevance for motor applications.
The working parts of a basic electric motor include:
- Fan
- Windings
- Commutator
- Field Poles
- Shaft
- Coils
AC Motors
DC Motors
Fan Motors
There are many varieties of fan motors. Fan motors are electric motors that allow fans to run regularly over a long period of time. The type of fan motor necessary depends on its application.
- Single-Phase Fan Motor - Single-Phase motors are the most common electric fan motors, as they connect with most smaller sized fans and operate on existing (AC) power sources. Each cycle dips and tops as electrical power increases, making it an electric motor which runs off a reduced amount of electrical power. This process is low-cost and puts little pressure on the electric motor's mechanical functions.
- Single-Phase Electric Motor - Split-phase motors are used for big commercial fans, or fans in larger devices which run off of a medium amount of electricity. These motors have start and run windings, both of which are stimulated when the motor is activated. Split-Phase Electric motors have built-in safety features that allow them to automatically shut off to prevent burn-out.
Servo Motors
A Servo Motor allows for precise control of position. Feedback and angle of the motor is controlled via a control box in this type of motor. Servo Motor applications include laser cutting machines, robotics, CNC machinery or automated manufacturing.
How to Choose an Electric Motor
This electric motor diagram shows a typical four-pole DC Motor,
assembled and disassembled.The electric motor diagram also depicts
the windings, commutator, field poles and shaft of the DC Motor.
- Cross reference the manufacturer's part or model number from the motor itself. This information is usually on the nameplate of the motor.
- If this information is not readily available, attempt to match the electrical specifications and physical dimensions of the defective motor.
- What are the electrical specs? - (typically found on the nameplate of the motor)
- HP, Volts, Amps, RPM's, Service Factor/SF (if applicable)
- What speeds do I need?
- Rotation (CW, CCW, or Reversible)
- Phase (1 or 3), in the case of appliance or industrial applications
- What are the physical dimensions?
- Frame size (if provided) -or-
- Length and Diameter of the Electric Motor, and
- Length and Diameter of the Shaft
- Number of Shafts (1 or 2)
- How should I mount this Motor?
- What is the mounting style of the Electric Motor? (rigid base, belly band, thru-bolts, cradle base, etc...)
- Vertical or Horizontal?
- What type of Enclosure do I need?
- Is the Electric Motor open drip-proof (ODP), totally enclosed air over (TEAO), totally enclosed fan cooled (TEFC)?
- Does it require special protection (i.e. hazardous location)?
- What additional specs are needed?
- Ball or sleeve bearing?
- Motor type (shaded pole, permanent split capacitor (PSC), capacitor start, etc...)
- Motor application (to what is it attached?)