A switch is a broad-spectrum term that can cover anything from a simple on/off push button, to the more complex type of current protection device used in industrial applications. The main functions of a switch are to make or break an electrical circuit – and to protect human beings against the risk of electrocution. They're also designed to help prevent or limit any damage to circuit hardware by minimising over-current situations and short circuits.
Push buttons are switches that make temporary contacts, and are ideal for low-voltage control circuits. They can be configured as normally open (NO), normally closed (NC) and sometimes both. Motor control switches are generally used to operate typical squirrel cage motors, with contactors rated for AC3 or AC4 duty. They'll be found in contactors of various types, including those with reversing, non-reversing and star-delta configurations. These switches are also found in contactors with a built-in tripping feature.
Motor control switches are rated for specific power and voltage inputs and must only be operated within their specified limits. The maximum current rating of a switch designates the highest current level at which they can function safely, from as little as 6A up to 200A. At Rowse Automation we can supply a variety of motor control switches, with current rated options for both simple and more advanced applications.
Isolator switches are produced for many types of application and in a variety of models. Those intended specifically for industrial use are usually designed as an enclosed block, made of strong technopolymer materials and available in a variety of colours. This type of switch is typically IP65-rated for use in industrial applications. Isolator or disconnect switches work by creating an air break, which physically isolates one or more sections of a circuit. This type of switch can also have an internal fuse, to provide a secondary level of safety by blowing and thus breaking the circuit. Fused isolator switches are rated according to the highest current level at which the individual fuse can function before it will blow. This may differ from the maximum current rating of the switch circuit.
Switches are also categorised by the number of throws (or positions) they can adopt, and the number of poles (or conductors) to which they can connect. At Rowse Automation you can choose from two, three or four-pole switches in a variety of external dimensions. Double pole isolator switches are used to control two circuits and are generally used for powering machinery up or down. Triple and four-pole isolator switches are commonly used with more complex electrical installations and equipment.
You connect an isolating switch upstream of your power circuit. It isn't horsepower rated and therefore isn't intended to interrupt the current flow. This type of switch isn't designed to control your motor's operation, but is used for lockout purposes once it's properly shut off. You'll find isolating switches with differing numbers of pole contacts, but for lockout purposes, they must have only one throw option.