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Interpower Corporation P.O. Box 115 100 Interpower Avenue Oskaloosa, IA 52577 (USA)
Copyright 2009.
All Rights Reserved
Interpower Corporation P.O. Box 115 100 Interpower Avenue Oskaloosa, IA 52577 (USA)
Copyright 2009.
All Rights Reserved
Interpower Corporation is delighted to send you the November edition of the Interpower Connections. This edition looks specifically at the benefits of specifying a multifunction power entry module instead of the individual components themselves. To also assist you with specifying the correct power entry module, Interpower Corporation is offering, for free, our Interpower Power Entry Module Wall Chart. You can download the wall chart as a PDF, print it off and post it or save a copy for future reference. Upcoming editions will take a look at other subjects that we hope will be of interest to both experienced and new designers alike. Should you have a question that Connections has yet to answer, please email us at info@interpower.com.
Over the years design and manufacturing of electrical and electronic equipment has evolved into smaller and more efficient products, and continues to do so. Manufacturers continually look for innovations and improvements that will keep them at the front of their industries. Part of this movement includes a desire to make products:
• More cost effective to build
•
Smaller
•
Easier and quicker to assemble
•
Safer
•
More attractive to the customer.
Component selection for front and rear panels often comes into play with this strategy. Fortunately, multifunction power entry modules provide a means to achieve the desired results mentioned above. A multifunction power entry module is a group of common front or back panel components that are placed together and conveniently packaged in a single unit. Let’s take a more detailed look at how multifunction power entry modules can help meet each of these goals and how to specify the correct module for an application.
Saving Space: Multifunction power entry modules combine multiple components into a single compact space in relation to the panel area of the equipment. This often leads to much less space wasted behind the panel. This benefit gives the manufacturer the luxury of either making the panel area smaller, increasing or enhancing functionality for other devices on the panel, or potentially decreasing the entire size of the equipment. Modules also tend to look much nicer on a panel, than having numerous, odd shaped parts spaced out all over the panel. This allows manufacturers to be more innovative with designs, which often leads to sleeker, more modern looking equipment, which may influence sales.
Lower Component Management and Cost: Multifunction power entry modules rarely cost less when compared directly to the individual component costs. However, by incorporating a number single components into one item, this allows reduced storage space in the warehouse, decreases incoming inspection time, reduces the amount of documentation and files for separate parts that need to be developed and kept, decreases the amount of testing and engineering time, and makes purchasing simpler. All these factors add to further cost and time savings. In addition, assembly labor is reduced. No longer do assemblers need to mount numerous different parts (requiring different tools), and be concerned with running wiring harness from one component to the next. Instead, the assembler can quickly fit one part into the panel, with minimal tooling and far less internal wiring. Many modules utilize quick disconnect (QD) terminals, which allows for assemblers to quickly and easily connect wires to the modules.
A Safer Product for the Customer: Most multifunction power entry modules are designed with a feature that prevents an equipment user from changing fuses or switching the voltage selector, without first removing the power connector from the inlet. This ensures that the power is removed from the equipment while these changes are being made, drastically reducing the risk of electrical shock to the user.
Selecting the Proper Multifunction Module: Multifunction Power Entry Modules typically can incorporate up to 5 functions: power inlet, circuit protection, switching, voltage selection, and filtering are the most common. When designing for an application, one must first consider which of these options are desired in a power entry module. Some functions have options that also need to be considered when specifying the module.
Power Inlet: Most multifunction power entry modules are centered around the use of the IEC 60320-1 C14 inlet. Typically (unless derated by another component in the module), these inlets are capable of a 10A rating for international use and a 15A rating for North American use. There are other power entry modules on the market for the lower 2.5A C6 and C8 inlets, as well as a few power entry modules utilizing the 16/20A C20 inlet. Because the C6, C8, and C20 multifunction modules are not as common or popular, it will likely be more difficult or impossible to find some option combinations.
Circuit Protection: Some applications may require circuit protection be included in the multifunction power entry module. A few multifunction power entry modules on the market now offer a circuit breaker for circuit protection. But because of the overall size and cost of most circuit breakers, this limits the number of options available while still maintaining the advantages of the multifunction module. Due to these considerations, the fuse has remained at the top as the means of circuit protection most commonly found in modules. When specifying a module that will use fuses, it is wise to consider the size of the fuses to be used. A few modules will accept both the 5x20mm size fuse and the ¼ x 1 ¼” fuses. Other modules are designed to only use the smaller 5x20mm size fuses. Since this size is available in versions for both North America and international use, it makes the modules an acceptable choice. Multifunction power entry modules that use only the North American ¼ x 1 ¼” fuses would not be acceptable for international use, due to the fact that this fuse is not widely available around the world.
Switching: If specialized switch requirements are not an issue, it may be desirable to specify an ON/OFF rocker switch as part of the multifunction power entry module. Module specifications should be examined to determine whether switches are SPST (Single Pole, Single Throw) or DPST (Double Pole, Single Throw) and whether or not they are lighted.
Voltage Selection: This commonly misunderstood function is often specified when it really isn’t necessary. Over the years, universal switch mode power supplies have been making the need for voltage selection obsolete. Equipment utilizing these power supplies has the ability to take any input voltage (generally within the range of 90V to 260V) and use it with no special adjustment needed by the user. Voltage selection is only needed in an application where a single input voltage level is required by the power supply or equipment. Voltage selectors allow the user to switch between 2 or more different input circuits connected to the primary of a multi-tap transformer, in order to ensure that the voltage needed by the equipment on the transformer output is always the same voltage level. For example, a machine that was dedicated to running on 120V could be designed with a transformer and voltage selector so that it could be used overseas. When used in North America at 120V, the voltage selector would be set at 120V, choosing the circuit that makes the transformer a 1:1 isolation transformer, passing the voltage through without changing it. If this equipment were sent to Europe, the voltage selector would be switched to 230V, choosing the circuit that is prewired to set the transformer up as a 2:1 step-down transformer, changing the voltage from 230V to approximately 120V on the transformer output.
Filtering: Specifying multifunction power entry modules with filters requires the engineers to make several decisions, based on the application needs. There are basically two types of filters readily available as part of a module. They are the standard EMI/RFI filter and the medical grade EMI/RFI filter. Standard filters are designed to attenuate both common mode and differential mode noise that might try to enter or leave the equipment through the power input connection. Medical filters are intended to do much the same, however, because of low leakage current requirements for patient connected medical equipment, the capacitors in the filter between the line and ground, and the neutral and ground have been removed. This causes medical filters to be much less effective against common mode noise, but drastically reduces leakage current which could be dangerous to the patient.
Another consideration that needs to be made is whether the filter needs to be shielded or not. Shielding provides additional protection against noise being radiated into or out of the equipment through the air. Any time a cutout is made for a component, this leaves a hole in the chassis where noise could radiate into the equipment. Shields on modules allow the manufacturer to essentially cover this hole by terminating the metal shield on the module to the chassis itself.
Finally, before settling on a filtered multifunction power entry module, it is essential that samples be obtained and tested to measure the effectiveness of the filter in any application. Filter effectiveness will vary, dependant on the frequency of the noise, the magnitude of the noise, the components in the filter, and by the equipment's impedance and loading affects. Testing is the only way to ensure that the correct filtered module is specified.
By utilizing this information and working closely with potential module suppliers to obtain specifications, certifications, and samples for testing, this will help ensure that you specify the right module for your application and realize the full benefits of utilizing multifunction power entry modules in your equipment and processes.
Interpower’s 3-function power entry modules combine the functions of a general purpose RFI filter with an IEC60320 C14 inlet, and either fusing or switch capabilities. These shielded modules are rated from 6 to 10 Amps and carry UR, CSA and VDE approvals. Interpower houses over 4 MILLION components in their warehouse so their customers don’t have to! As always Interpower offers no minimum order requirements, and specification sheets and pricing are available on line. Place your order on line at www.interpower.com or call our Customer Service Department at (800) 662-2290. Same day air shipments are available for stock item orders received by 6:00 p.m. CST.
Here is your chance to request your free copy of our Interpower Power Entry Module wall chart. The Interpower Power Entry Module wall chart will make it easy for you to specify the module you need, when you need it. With this handy wall chart, you will be able to find the Interpower part number you need, easily and quickly. Click on the chart to download your copy or visit us at http://www.interpower.com/ic/maillist.asp and enter "modules" in the title to request a copy be sent to you.