Hospital-grade Filtered Module Issue?

Q: We bought module 83545020 from you to replace a broken one we purchased from a different vendor. We have installed it, but it’s not getting any current. Is the module bad, or are we doing something wrong?

A: Thanks for the question. It sounds as if you have checked your connections and made sure you have given the fuse drawer a shot of air. If everything appears normal, and there is no sign of corrosion or arcing, my next question is whether you have tried using the old fuses from the previous module to see if the new module works? Sometimes ordering standalone fuses on the Web can be confusing and you may have the wrong size or amperage. Please let me know after you try it . . .

Q: We simply didn’t consider using the fuses. But yes, we called and got the specs from the manufacturer and sure enough, the fuses we bought have us up and running. Lesson learned!

A: Great! It’s good to keep in mind that module manufacturers and distributors never include fuses with the modules as they don’t know what size and amperage rating would be needed for any given application, and to arbitrarily put one in is to invite a disaster and a subsequent liability issue. It is always the equipment manufacturer who determines what fuses are needed per a module model, and the end user’s responsibility to replace the fuse if it should blow. I’m adding a graphic which may help you and your colleagues replace any future fuse issues.

Per the graphic (below), the two fuses go in from the sides. Remove the front panel from the circuit protection drawer to replace fuses, being sure to rotate the voltage selector to the proper voltage. Copying fuse placement from the old to new will work also. If you have any need for assistance with these illustrations, please feel free to contact us.

Protecting Hospital Testing Equipment from EMI/RFI

Q: For sensitive hospital testing equipment, what is the optimal way to keep EMI/RMI to an absolute minimum for patient safety and interference?

A: Good question. First, I would look at it more from a design angle than a set of procedures or specialized equipment. I say this because electrical cords themselves, no matter how long the cords are, create EMI—the longer the cords, the more EMI. So, right off the bat you can cut down on minimal EMI/RMI by shortening your electrical hospital-grade cords.

Second, I’d make sure your sensitive testing equipment is measured in microamps (µA) versus milliamps (mA)—1 million microamps is equivalent to 1 ampere, and 1,000 milliamps is equivalent to 1 ampere. So, if the equipment is either attached or near the patient, I’d recommend using (µA) versus mA to increase patient safety.

If the equipment is away from the patient, electrical devices using mA are safe to use in a hospital setting. However, if you are in a room with several power cords powering several machines or devices, say you have 4–8 outlets and the one inlet in your accessory power strip, and most of the outlets are being used, you may already have maximum “noise” interfering with sensitive hospital-grade equipment.

In that case, going back to µA-rated equipment is one of several options. You could add filters to your power modules, which offer very low leakage, say between 2–5 microamps µA. You could also replace the standard hospital-grade cords with shielded cords, which offer another layer of protection. For example, our modules produced for the medical field offer full shielding—the components are housed inside metal, and the EMI gets shunted away from the module and into the ground line.

Standard nonmedical filters are typically rated between 0.25 and 0.50 mA which is considered minute leakage in most other industries, since it takes roughly 10 mA to produce a shock, or 10,000 µA. However, to start, I’d recommend that each of your hospital-grade cords stay inside the 12- to 15-foot range. Otherwise, you won’t be able to meet the standards required for equipment such as heart monitors and life-support equipment.

Hospital-grade modules can be found at Hospital-grade module. Other topics such as cord length, cord length calculation, EMI/RFI, bend radius, molding and ultrasonic welding can be found by clicking on the Interpower home page at https://www.interpower.com/ic/designers.html. There you will find an encyclopedic repository of power cord and component content such as videos, webcasts, white papers and the blogs (InfoPower and Connections). You can also click on our product pages to get the exact specifications and materials of our modules, filters, and power cords. You may also want to peruse the information we have on capacitors, ferrites and ferrules as well.

In conclusion, you can also click on our product pages to get the exact specifications and materials of our modules, filters, and power cords. You may also want to peruse the information we have on capacitors, ferrites and ferrules as well.

Country-specific Compatibility

Q: I recently left the UK to move to Brazil, realizing too late that the UK mains power is 220VAC and Brazil is 127VAC. I brought lots of UK electrical devices with UK styled three-pin plugs with me. The UK plugs have a built-in fuse contrary to plugs here in Brazil. My question is, instead of using plug converters to bridge the difference between the UK device plug and the wall socket, would it be safer to replace the device‘s cable with a Brazilian-styled cable and a Brazilian standard plug without a built-in fuse? Do UK devices have an additional fuse or safety system built inside of them to minimize surges?

A: The answer to your question depends on the individual device. You will need to locate the electrical ratings for each device. These will most likely be on a label, or could be embossed or intaglioed onto products of plastic or rubber—especially the amperage rating. When the voltage goes down, the current draw increases, so you will want to ensure that you are not over drawing from the building circuit for bigger devices. If that is the case, you may need to consult a local electrician, as there is a 220V system in use in Brazil that utilizes a different plug in either 10A or 20A versions.

There are three different scenarios and solutions you may encounter with varying voltage input ratings:

1. Single voltage rating (example 230VAC) or very narrow range, e.g., 220V–240V. In this instance, the device is dedicated to the specific voltage or very narrow range, and will not function at all or properly on 110V. There are only two options for these devices: purchase a voltage converter for each device (expensive and hard to find) or replace the device with one purchased locally.
   
   
2. Dual voltage device, e.g., 110V–220V. These devices would likely have a voltage selector switch or module on them that would need to be positioned to the correct voltage. Once the correct voltage is selected on the device you can use a travel adapter to power it with the original cord.
   
   
3. Device with a large voltage range, e.g., 110–240V. These devices have a universal power supply circuit and will take any voltage and convert it internally. For these you can either use a travel adapter or simply replace the cord in the case it is detachable (has a removable connector that plugs into the device).

The UK plug is fused due to their unique ring wiring system. In Brazil, it should be a linear wiring system, so fused plugs aren’t needed. The fuse in the UK plugs won’t have any effect on the use of an adapter and you won’t need to worry about fusing in the plug if you replace the cord. Hope this helps.

British Fuse Options and Chart

Q: I purchased a standard British power cord that has a 10A fuse in the plug for a device we make. We have developed a new product that only draws about 2A, which we now have a UK order for. I wondered if I could get a UK power cord with a smaller fuse? Or if I can get a lower amperage fuse to swap out the current 10A fuse?

A: The answer to both questions is “yes.” Per British power cords, there are four different fuse amperages: 3A, 5A, 10A, and 13A—the fuse amperage must be clearly marked on the cord set or fuse, or preferably both. Interpower makes BS 1362 British power cords with the customer’s choice of fuse already in them. Also, replacement fuses are available in all four sizes—you can swap out one fuse for one of the other sizes if you label the product appropriately. So, for your 2A product, the 3A fuse would be a good recommendation. It should be noted that these fuses are uniquely sized fuses used only in UK plugs—you’ll need to make sure you’re ordering BS 1362 replacement fuses as metric size fuses will not fit. Interpower Corporation makes OEM BS 1362 cord sets and carries replacement fuses in all four sizes. I have included a British Standards chart to provide you additional information. (Below.)

Ferrites with North American and International Cable

Q: Are there off-the-shelf molded options that accommodate our need for unshielded cables with ferrites? And could we use the ferrites with North American and international cable? 

A: The answer depends on the cable you’re using. Ferrites were invented in North America, and thusly designed with American Wire Gauge (AWG) outer diameters in mind. We have tried to locate ferrites for molding on the other cable types found around the world (common international diameters), and they will not properly mold onto the cord as the resin can creep between the ferrite and the cable jacket, fracturing them. Therefore, we only offer snap-on ferrites on international cable types. Be sure that you’re not using AWG cable for international purposes since agency standards prohibit that; and if you try to use a non-North American plug on North American cable, you may have voltage differences that could lead to dangerous electrical hazards.

Difference in North American/International Currents

Q: Wondering if you can tell me the difference between international current rating & North American current rating for Part Number 83020131? Also, if possible, please send me a diagram to better understand the dimensions of the part. Appreciate your quick response.

A: The International rating for this part number is 10A/250VAC (maximum), and the North American rating is 15A/250VAC (maximum). The ratings are set by agency standards IEC 60320-3 under “Appliance Couplers For Household And Similar General Purposes—Part 3: Standard sheets and gauges” that follow in “Table 2.” You will find the table and the Sheet F rating on page 11 of that document.

However, I can save you the trouble of looking that up: Internationally, the IEC 60320 standards limit this particular configuration (Sheet F) to 10A. In North America, UL and CSA use their own version of the standard, e.g., UL 60320-3, determining that the configuration is capable of 15A. Thus, the dual ratings, one for North America and the other for international. Also, I will note that the rating is for the entire device, so if you are using all four Sheet F outlets in the accessory power module, the total current draw between all four cannot exceed the stated rating, e.g., 1.5A + 0.75A + 2A + 5A = 9.25A would be acceptable for use overseas; a sum exceeding 10A would not. I have attached a drawing of the part. Please let me know if you need any further information. Thank you.

Electrical Arcing Scare

Q: We experienced a problem with an IEC 60320 Sheet E rewirable connector plugged into a Sheet F outlet. The pins are discolored, and part of the Sheet F melted. Can you determine whether this was a quality issue or something we did wrong? Thanks.

A: Thanks for your question. The photos you sent were a great and immediate help. For those who do not understand the purpose of the tapered end of a plug pin, it is designed to insert into the female contact and open it up as to let the rest of the pin slide more easily into the female contact. Once the plug is fully engaged, the front end of the pin will exit the opposite side of the female contact and plays no role in further creating further damage.

The discolored area on the tip of your pin is the result of arcing that has occurred. You can actually see that the plating has been blasted and flaked off due to prolonged arcing, and has pitted the deteriorated metal to the point of discoloring it. The solid edges are actually nonexistent as much material has been blasted away. This is called pitting. The discoloration is a combination of this and residue that has been left behind by the arcing process.

The “ground zero” of the arcing shows a shallow crater with some deeper pitting. This is a textbook case, one that it is instantly noticeable. I’m doubly grateful you sent the images—this is great training material that may potentially save equipment, infrastructure, and possibly even lives.

So why is the damage so telling? A theme from the real estate industry: location, location, location. The only way arcing can occur where it did is because the plug was not fully engaged into the outlet at the time of failure. It is only possible to arc at this location if the pin is resting directly at the front edge of the female contact, yet not enough to make an actual connection. Once the pin starts into the contact, the rest of the pin against the contact is enough to conduct (i.e., physical connection is made and resistance becomes near zero), and arcing would cease. And, when the pin is fully engaged in its normal position, it emerges outside the other end of the contact, and again, arcing could not occur due to the near zero resistance potential and the positioning of the pin end in relation to the female contact. Thus, this one photo has allowed us to pinpoint the failure and eliminate all other possibilities we have previously discussed as potential causes.

The exceptionally “hot” pin in the outlet melted the outlet’s pin slot. All other damage to both parts is a result of the intense heat caused by the prolonged arcing and is collateral damage from the event. There are only three root causes that can explain the positioning of the pin being a location causing it to arc, or a variation thereof of 1–3 may have occurred:

• Plug vibrated out until partially left in outlet.              
• The plug was not properly inserted into the contact.
• Plug was inadvertently moved enough as to lose contact.

Regardless, it is obvious that the issue occurred solely on how the plug and socket was used in the application, and not the quality of material. This is why it’s important to make sure plugs are inserted all the way. Also, it’s important to notice the slightest trace of arcing electricity—it’s the AC power equivalent to putting a match on kindling to start a fire.