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More Information on Power Entry Modules

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Modules

A module simplifies the power entry element by combining multiple functions into a single unit.

When designing an electrical or electronic product, the most common means of connecting a detachable cable to equipment is the IEC 60320 inlet. Once the cable assembly is connected, other components are necessary to control the electrical power, protecting the equipment and the user. When added individually, these components can create clutter on the equipment and a wiring problem on the inside. To simplify the problem, a module provides multiple power entry functions and various forms of protection and control in one compact unit.

Benefits

Interpower power entry module on equipment saves panel space Components mounted individually on equipment panel use more panel space

A module has a number of benefits over using individual components.

  • Saves panel space—Several components combined into one module reduces the mounting hole size, whereas components mounted individually on the equipment use more panel space.

  • Reduces assembly labor—Installation labor costs can be reduced as the combination of several components into one package reduces the number of components handled. Assembly labor costs may also be reduced because there will be less internal connections to make.

  • Lowers components management and costs—Reducing the number of components used in equipment decreases valuable engineering time of testing and documentation for individual component and agency approvals. There is also a reduction in inventory.

  • Increases user safety—The risk of accidents is decreased. The design of most modules makes it necessary to remove the power cord assembly from the unit before making any changes. Interlocking the power entry connector to other module functions reduces the probability of accidental shock by the user.

Functions, Mounting Orientation, and Connection Styles

When selecting a module, the first step is to determine which functions are needed, along with the mounting style. Modules are available with a variety of component combinations and different mounting styles.

Functions

module drawing
exploded module view
This is one example of a module. There are different styles and various combinations of functions that can be included in a module.

Interpower’s modules may have from two to five functions. These functions include: inlet, outlet, switch, circuit protection, filter, and/or voltage selector.

Inlet

The power inlet is responsible for bringing electricity into the unit via connection with a detachable cord set. The most common inlet is the IEC 60320 C14, although other IEC 60320 style inlets, such as the C6, C8, and C20, are occasionally offered by some manufacturers.

Outlet

An outlet is an IEC 60320 connection device that provides access to electricity from a power source.

Switch

The switch is used to turn the power on (“I”) and off (“O”) from the module to the rest of the unit. Rocker style switches are the choice of many module manufacturers. Some modules use a double-pole, single-throw switch and others use a single-pole, single-throw switch. While unlighted switches are the most common, they can be either lighted or unlighted. When choosing a module for an application, it’s important to note the orientation of the switch markings. The “I” marking should be vertical when mounted.

horizontal switch vertical switch
Switch for horizontal mount applications  Switch for vertical mount applications 

Circuit Protection

Circuit protection takes the form of a circuit breaker or a fuse. Both provide current protection to the equipment, reducing the possibility that a short circuit can damage the equipment or harm the user.

  • Circuit Breaker
    A circuit breaker is a switch that provides on/off and circuit protection capabilities.

  • Fuse
    One of the most common functions available in modules is fusing. Fuse holders and carriers are commonly built into modules so the fuses can be installed to provide circuit protection against abnormal surges and overloads. When determining the amp rating of the fuse, it should not exceed
    the overall rating of the module.

    • Single-Fuse and Double-Fuse
      Most modules with fusing capability must be specified as needing either single-fuse or double-fuse capabilities depending on the applicational needs. Some have the ability to be configured either way by the addition of a mechanical shunt or by using a dummy fuse in one of the two fuse locations.

    • Fuses Never Included in the Module
      It is necessary for the customer to realize that modules never come with fuses in them. It is impossible for module manufacturers to install fuses into a module without the customer’s permission and guidance due to the lack of applicational knowledge and for liability reasons. The customer must order the correct fuses separately and install them or specify the correct fuse needed and order them installed as a value-added option at an additional cost.

    • International and North American Fuses
      It is also worth noting that some modules can accept both the international 5 x 20mm size fuses and the ¼ x 1¼-inch size fuses commonly used in North America while other modules are designed to only accept one specific size fuse. It’s important to check fuse size specifications of any module being considered in order to choose the best one for a specific application.

      fuse mounting
      This is one example of how a fuse may be inserted into a fuse drawer. Also, some modules may have included extra space into the design to carry a spare fuse.

Filters

Filters play an important part in equipment design, especially in high frequency and medical equipment applications. The circuit components of filters are inductors and capacitors. The difference between a standard filter and a medical-grade filter is that capacitors between the circuit conductors have been removed in the medical versions in order to decrease leakage current values. This is important for equipment where leakage current values are tightly controlled by safety standards in order to ensure patient safety.

Interpower filtered power entry modules are available with or without a metal shield, typically specified in high frequency applications. An RFI/EMI filter is an electrical circuit that is designed to remove radio frequency and electromagnetic interference (noise) from the equipment. This prevents malfunctions due to interference and also prevents the equipment from radiating noise, which might interfere with other equipment.

When specifying a module with a filter, it is necessary for a company to obtain samples to test with one’s application to ensure it will perform as desired. This is because filter performance specifications are based on an industry standard 50 ohm test circuit and certain aspects of an application’s design may alter the way a filter performs when the circuits are connected.

Voltage Selector

Voltage selection allows equipment to be designed and manufactured to operate on approximately 115 or 230VAC. A voltage selector changes voltage by changing connections on the transformer. By changing the selection, this allows the user to define the correct input voltage. Voltage selection changes are made by removing the fuse holder and rotating it. It is important to note that the voltage selector is a specialized switch which works in conjunction with a transformer that is designed into the customer’s equipment. The transformer is not part of the actual module, but it creates alternate circuit paths for the voltage selection process. If the customer has a switched mode power supply (which is any power supply between 90-264V), then a voltage selector is not needed.

Mounting Styles

Interpower modules are available in both snap-in and screw-mount versions to meet design requirements.

Snap-In

The snap-in style permits the manufacturer to cut a mounting hole in the equipment and slide the module into the hole. The locking tabs snap into place, firmly holding the module to the panel surface.

Screw-Mount

The screw mount style has an enlarged flange on the sides providing a place for mounting holes. The equipment panel is drilled for screws or tapped for bolts.

PC-Board Mount

A PC-board mount (printed circuit) style is both a mounting and contact style. The inlet/outlet is soldered directly to the PC board. It is then mounted to the equipment chassis. This application is used in high volume applications involving quick assembly time.

Connection Styles

Conductor connections are made in three ways: QD (Quick Disconnect), solder, or PC-board.

QD (Quick Disconnect)

Quick disconnects are a quick and easy method of making conductor contacts on modules. The QD contact on the module is a small flat, spade-like connection which the QD attaches to. QDs make an easy, solid electrical contact for conductors and are available in 4.8mm (3/16-inch) and 6.3mm (1/4-inch) sizes.

Solder

Solder tabs are similar to QD connections. Solder tabs are small, flat, spade-like connections. Each connection has a small hole in it sized to insert a wire. Once the wire is inserted and folded over, solder is applied.

PC-Board Mount

PC-board tabs are small flat pins that extend down from the back of the module. The module is placed on the PC board, the contact pins are inserted into the footprint, and solder is applied to make the electrical connection.

Ratings and Approvals

Ratings

Ratings on modules are based on the components making up the module. Like power cords and cord sets, the weakest principle applies. The lowest rating on a component will determine the total rating on the module. Ratings fall into two categories: amperage and voltage. A module’s maximum overall current rating is based on the lowest rated component. If a module’s inlet is rated for 6 amps, switch at 15 amps, and the voltage selector at 10 amps—the module’s overall rating is 6 amps. Voltage ratings are set at the highest level the component can be used. Interpower modules are rated up to 250VAC. A component rated at 250VAC can be used in a 125 or less VAC application.

Approvals

In regards to many of the modules offered by Interpower—most of the components within these modules meet the requirements of the UL, CSA, and/or VDE or international testing agencies. A few modules have approvals on components from different testing agencies.

Hospital-Grade Power Entry Modules

Hospital-grade equipment must meet special requirements. These requirements place special significance on fusing and filtering when selecting components used in medical equipment. Patient-connected medical equipment can be subjected to low-leakage current requirements. The use of a low-leakage filter in the 5μA range at 250VAC is desirable. In addition, fusing of both line and neutral connectors may be required (i.e. double fusing).

Types of Modules Available at Interpower

Interpower offers two, three, four, and five function modules with a variety of component combinations. Hospital-grade modules are also available.

See the complete line of modules available at Interpower.