Many electric switches interrupt circuits by creating an air gap between contacts. The contacts must separate quickly for proper operation.

In electronic switch designs, circuit state changes occur by adjusting connection resistance. Increased resistance opens the circuit, while decreased resistance closes it. These switches often lack moving parts.

A crucial consideration is the switch's response to its actuator. The actuator, whether automatic or manual, is essential for making or breaking the circuit. It initiates circuit state changes and may include physical elements like levers or respond to conditions such as overvoltage or light variations.

When equipment protection is needed, a fuse is often integrated into the switch assembly.

Chapter 2: Ratings and Categories of Electric Switches

This chapter covers various ratings and categories of electric switches, providing essential information for electrical engineers, facility managers, and those involved in electrical component selection or installation.

Rating of Electric Switches

When selecting electric switches for industrial, commercial, or residential use, consider their ratings to ensure safe operation. These ratings determine switch suitability for different electrical loads and environments, including:

• Current Rating - The maximum current a switch can carry, measured in amperes (A). Exceeding this rating may cause damage, overheating, or fire hazards.

  
  

  For circuit breakers, the rating indicates the current threshold for tripping. Breakers often allow slight overloads before tripping, specified as a percentage of rated current.

  Electronic switches like MOSFETs and relays also have current ratings; exceeding these may affect performance or lifespan.

• Voltage Rating - The maximum voltage a switch can withstand, measured in volts (V). This prevents arcing, insulation breakdown, or damage during operation.

  In electronic switches like thyristors, the voltage rating represents the highest blocking voltage in the off state. Exceeding this may cause failure, especially in high-voltage applications.

• Power Rating - The total electrical load a switch can handle safely, measured in watts (W). important for high-power applications like motor control and industrial machinery.

• Environmental & Mechanical Ratings - Includes IP ratings for dust/water resistance and UL/IEC certifications for safety compliance. Mechanical endurance affects reliability in demanding applications.

Switch ratings differ for AC and DC circuits due to varying breaking characteristics and arcing behavior.

AC Circuits: In alternating current circuits, voltage periodically drops to zero, helping extinguish arcs when breaking the circuit. AC switches often have higher voltage ratings than DC equivalents.

DC Circuits: Direct current's steady flow causes prolonged arcing, requiring faster switching and arc suppression. DC switches typically have lower voltage ratings than AC versions.

Understanding and selecting proper switch ratings ensures safety, compliance, and optimal performance in electrical systems.

Categories of Electric Switches

Electric switches can be classified by function, design, and application environment. Primary categories include:

Momentary Switches

Momentary switches maintain one state until actuated, then return when released. Common in push-button switches, tactile switches, and emergency stops.

Early examples include telegraph machine switches. Used in control panels and security systems for temporary contact.

• Normally Open (NO): Closes when energized, opens otherwise. Used in standard push-buttons.
• Normally Closed (NC): Opens when energized, closes otherwise. Used in safety interlock systems.

Maintained Switches

Also called "latching switches," these remain in their state until toggled again. Examples include light switches and car ignitions.

Preferred for stable connections without continuous actuator pressure, such as lighting control.

Additional Switch Types

Specialized switches address unique requirements:

• Rotary Switches: Select among multiple circuits via knob rotation.
• Proximity Switches: Detect object presence without contact.
• Limit Switches: Provide position feedback or movement limits.
• Selector Switches: Choose between operational modes.
• Reed Switches: Magnetically operated for sensing applications.

Understanding these categories helps select appropriate switches based on contact type, operation, and safety features.

Chapter 3: Types of Electric Switches

Electric switches are essential control points in electrical systems. This chapter explores various switch types based on design, mechanism, and application.

DIP Switch

DIP (Dual Inline Package) switches are compact PCB-mounted switches for device configuration. Used in electronics manufacturing and testing equipment.

Electrical Switches

These open/close circuits to control current flow to devices. Different from electronic switches which use semiconductors.

Circuit Breakers

Specialized switches with automatic overload protection. Trip during excessive current to prevent damage or fire.

Fused Switches

Combine switch functionality with protective fuses for overcurrent protection in industrial systems.

GFCI Switches

Ground Fault Current Interceptors monitor current imbalance and shut off power during leakage, crucial for wet areas.

Plain Electrical Switches

Basic switches without integrated protection. Common in residential and commercial wiring.