What Is an Inlet?
Inlets are connectors used to connect AC power cables to electronic equipment powered by AC power.
They are called because they serve as the AC power inlet for electronic equipment. The advantage of using an inlet is that the AC power cable can be disconnected from the electronic equipment, allowing for AC power cable replacement and improved portability of the electronic equipment.
If inlets are not used, the AC power cable is pulled directly from the electronics. Note that two types of inlet mounting methods exist: screw-fastening and snap-in types.
Uses of Inlets
Inlets are used as connectors for AC power supply cables and are attached to the panel of an electronic device. AC power can be supplied to an electronic device by connecting the inlet plug of the AC power cable to the inlet of the electronic device and the plug of the AC power cable to a power outlet.
Inlets Principle
Inlets are 2- or 3-terminal female connectors into which male AC power cable inlet plugs are inserted. 2-terminal inlets consist of an N-terminal and an L-terminal, while 3-terminal inlets consist of an N-terminal, an L-terminal, and a ground terminal.
Types of Inlets
1. Multi-Functional Inlets
Multifunctional inlets that incorporate fuse holders, switches, and noise suppression filters also exist. The advantages of multifunctional inlets are that they enable the downsizing of electronic equipment, reduction of the number of components, and reduction of assembly man-hours.
However, the cost of multifunctional inlets is higher than that of single-functional inlets.
2. Inlets With Fuse Holders
Inlets with fuse holders are inlets that incorporate holders to which tube fuse-type fuses can be attached. Fuses can be replaced without disassembling the electronic equipment.
Since many components do not have fuses installed and wiring between fuse terminals and power supply terminals, fuse installation and wiring between terminals should be performed when the electronic equipment is assembled.
3. Inlets With Switches
Inlets with a locking switch. The switch is wired to the terminals of the Inlets, so no work is required during the assembly of the electronic equipment.
The 1-pole switch turns the L terminal and the device ON/OFF, and the N terminal and the device are always connected. 2-pole switches turn both the L terminal and the device ON/OFF and the N terminal and the device ON/OFF. A switch with a lamp is also available, and the ON/OFF of the switch is interlocked with the ON/OFF of the lamp.
4. Inlets With Noise Suppression Filters
Inlets with built-in noise suppression filters for AC power lines are effective in reducing noise entering electronic equipment from AC power lines and reducing noise emitted from equipment to AC power lines.
Inlets with built-in noise suppression filters have a greater depth than single-function inlets, so care must be taken to avoid interference with other components in the electronic equipment.
How to Select Inlets
1. Rated Voltage, Rated Current, and Rated Temperature
As with other connectors, select inlets rated for the voltage, current, and temperature environment in which the electronic equipment operates. Selecting inlets with higher ratings than necessary will result in larger inlet sizes and thicker AC power cables to be used.
2. Presence of Ground Terminal
There are two types of inlets: 2-pole and 3-pole. If the inlets do not require a ground terminal, select 2-pole. Conversely, if the inlets require a ground terminal, select 3-pole.
Other Information on Inlets
Shape of Inlets
Inlets are defined by the International Electrotechnical Commission (IEC), and there are a total of 11 types of inlet shapes. The two main types are spectacle-shaped and hexagonal.
Hexagonal inlets have a larger external size but a higher-rated current. Therefore, it is important to select the inlet plug shape of the AC power cable to be used according to the inlet shape.