Determining which type motor you need may not be an easy task. There are many different types available today. Before you order, there are a number of parameters that need to be addressed. So how can you properly accomplish motors? This article is written to assist you in determining which motor is best for your application.
First and foremost you will need to know what voltage source is available in your application. Electric motors can be classified as either AC (Alternating Current) or DC (Direct Current). Alternating current types only run on AC Voltage and direct current types only run on DC Voltage. There is also a universal motor that can run on both AC and DC voltages.
Once you have established which power source you have you will need to determine which style will work for your application. AC motors can be sub-divided into the following: Single Phase Induction, Three Phase Induction, Two Phase Servo, and Hysteresis Synchronous. DC motors can be sub-divided into: Brushless DC, Brush DC, and Stepper types.
Next we need to understand the different characteristics of each type in order to properly match a motor to its application.
A single phase induction motor is connected to a single voltage line. An external capacitor is required to make this motor operate. The different types of single phase induction motors are distinguished by which method they are started. The four basic types are: split phase, capacitor start, permanent split capacitor, and capacitor start/capacitor run.
A split phase motor uses a switching device to disconnect the start winding once the motor gets to 75% of its rated speed. Although this type has a simple design which makes it less expensive for commercial use, it also has low starting torques and high starting currents.
The capacitor start motor is basically a split phase capacitor motor with a capacitor in series with the starting winding to create more starting torque. This motor is more expensive on account of the switching and capacitor requirement.
A permanent split capacitor motor does not have any staring switch. For this type, a capacitor is permanently connected to the starting winding. Since this capacitor is required for continuous use, it does not provide starting power, therefore starting torques are typically low. These motors are not recommended for heavy starting load applications. However, they do have low starting currents, quieter operation, and higher life/reliability, thereby making them a good choice for high cycle rates. They are also the most reliable capacitor motor on account of not having a starting switch. They can also be designed for higher efficiencies and power factor at rated loads.
The capacitor start/capacitor run motor has both a start and run capacitor in the circuit. The start capacitor is switched out once achieving start-up. This type of motor has higher starting, lower loaded currents, and higher efficiency. The drawback is the expense that’s required for two capacitors and a switching device. Reliability also plays a factor on account of the switching mechanism.
The three phase induction motor is wound for three phase alternating voltage. These are the simplest and most rugged electric motors available. The motor could be designed for either DELTA or WYE hook-up. This type is designed for continuous use and high starting torques. Motor speed is relatively constant. If three phase voltage is available this is the motor to choose.