DC Power Supplies
Conditioning. Protection. A personal trainer who doubles as a body guard? These words actually describe the unsung duties (among others) of the direct current (dc) power supply. These devices provide power necessary for control systems to function. According to a recent online survey from Reed Research, of the nearly 600 control professionals responding, 78% are involved in specifying, recommending, and/or buying dc power supplies.
Of responders that dealt with these devices, 57% used them for in-plant requirements, 22% used them for OEM or resale requirements, and the remaining 21% used them for both in-plant and OEM requirements. Usage was further broken down into specific applications. Here responses indicated that 31% of those surveyed used dc power supplies for both continuous and batch processing applications. Discrete manufacturing applications accounted for 29% and continuous processing 16%. Utilities, batch processing, and other non-specified applications accounted for 10%, 5%, and 9% of the total, respectively. See chart.
Features for dc power supply selectors vary widely. Which features drive the recommendation and purchase? According to the survey, at 81%, reliability topped the list of features marked very important. Ease of maintenance claimed the number two spot, at 45%. Meeting space requirements was 43%, providing input overvoltage protection followed at 42%, efficiency and ease of use tied for fifth place at 41% each, ease of installation 39%, ease of upgrade 38%, active power filtering capability 32%, and ability to handle large power outrush 26%. See chart for the ranking of all 19 features named. The survey allowed multiple responses, so percentages add up to more than 100%.
Views about dc power supply manufacturers present additional criteria for those specifying, recommending, and/or buying these devices. Again the number one factor for choosing was product quality. Delivery (availability) rated second, price rated third, customer service rated fourth, and Website information availability rated fifth. Other factors that also made the list were: availability of technical assistance, previous experience with the manufacturer, Website purchasing capability (online catalog available), availability of a local sales rep if needed, and available training.
As with most control components, dc power supplies also are available in a wide variety of types, sizes, mounting styles, and footprints. Of the 14 power supply types listed in the survey as possible choices, there were clear favorites. Based on returns in the “currently use, will continue to use” category, the top five were 59% DIN-rail-mounted linear regulated; 49% DIN-rail-mounted high isolation; 44% standalone linear regulated; 33% miniature with screw terminals; and 33% rack-mounted linear regulated. Keep in mind that these types listed are only the frontrunners. Even remaining styles received a fair number of responses; indicating that even in the world of dc power supplies as elsewhere in engineering, the term “application specific” applies.
The purchasing outlook for dc power supplies is positive. According to respondents, 24% see an increase in their demand for them over the next 12 months; 67% expect to buy as many as they did last year; only 9% see a decrease in demand.
Advice from end users
As with all engineering endeavors, attention to technical detail is paramount in verifying the application needs and capabilities of the power supply being considered, according to control professionals who provided verbatim responses to the survey.
Advice offered included: Watch the noise and influence on sensor measurements; seek finger-safe terminals, internal overcurrent protection, and LED power on; and consider future needs.
In responding to the survey, Laurence Rogers, project manager, SNC-Lavalin Engineering, says, “Make sure it’s really going to fit in your enclosures and provide adequate ventilation/air handling with room to spare.”
Dean Pappas, senior design engineering, Finisar Inc., says, “Testing both line and load transient behavior in N+1 Redundancy configurations is far more complex than testing a single supply. This has a direct impact upon the load-sharing schemes chosen and possibly impacts efficiency.”
Dave Summers, engineer at Helios Coatings Inc., added, “Buy quality. Don’t skimp; it will bite you.”
Products: power supplies, dc
In the survey, respondents chose from the following as the most-purchased-from manufacturers of dc power supplies in the past 12 months (descending order): SolaHD, Rockwell Automation (Allen-Bradley), Lambda, Phoenix Contact, Siemens, Acopian, Power-One, Omron Electronics, IDEC, ABB, Schneider Electric (Square D), GE, Condor, PULS, Lucent, and Traco Power. For these and other manufacturers, visit www.controleng.com/buyersguide . For systems integrators, visit www.controleng.com/integrators . Also visit specific company Websites listed here.
Power supplies: Smaller, high efficiency, diagnostics
Sola/HD has introduced two new SDN-C power supplies in its 5ol cabinet, the SDN-C units reduce excess heat in the panel due to high efficiency and power factor correction design. www.solahd.com
DIN-rail power supplies
Allen-Bradley power supplies for DIN rails from Rockwell Automation increase application reliability and safety. N+1 redundancy modules provide a cost effective means for providing back-up power in the event the primary power supply fails. “Buffer” module adds reliability for brown-out conditions when input power is unreliable. Line of switched mode power supplies accepts wide ranges of ac and dc input voltages and has global certifications to meet worldwide single-phase and 3-phase application requirements. www.rockwellautomation.com
Harsh-use power supplies
Lambda extended its 500 W LZSa Series of industrial power supplies to include 1,000 and 1,500 W supplies with features and safety-agency approvals said to be not commonly found in standard off-the-shelf devices. A wide operating temperature range, compliance with MIL-STD-810E standards for shock and vibration, and ability to operate in explosive gas atmospheres are said to be ideal for factory automation, computing, automatic test equipment, petrochemical, control systems, and commercial-off-the-shelf uses. With nominal output of 12 V (LZSa1000) or 24 V (LZSa1000/1500), they feature wide user-adjustment ranges of 10 to 15.75 V and 18 to 29.4 V for non-standard voltage requirements. www.lambdapower.com
Selective fuse breaking power supplies
The Phoenix Contact Quint SFB family of power supplies are the first industrial grade devices to feature Selective Fuse Breaking (SFB), a technology that increases system reliability. SFB technology provides up to six times nominal current for 12 ms. Faulty current paths are shut down, while the power supply continues to deliver power to the other loads. Power reserve also is available for loads with high start-up current peaks. They also include expanded diagnostics. www.phoenixcon.com
Exclusive: Power supply reduces footprint
Siemens Energy & Automation Inc. introduced a new Sitop Modular 3-phase 24 V dc/ 20 A power supply (more on page 10) . Less than half the width of previous models, it is ideal for applications demanding small footprints. www.sea.siemens.com
Siemens Energy & Automation
Constant voltage, current power supplies
Acopian’s line of low profile switching power supplies has been expanded with the smaller WL7 Series, with 450 W outputs. All have constant voltage/constant current crossover. Models with wide output voltage ranges can be adjusted down to 0 V, and both voltage and current can be programmed with 0-10 V control voltage inputs. Voltage and current monitor outputs and an inhibit terminal are included on the pluggable connectors that enable easy wiring of the control and input leads. www.acopian.com
Acopian Technical Products
Load converters, high density
Power-One has introduced three new high current point of load converters. These 40 A, 50 A, and 60 A devices use multiphase-synchronous-buck topologies to deliver up to 93% efficiencies in high-power density packages for space-critical blade server and communications applications. Wide input ranges (5 -13.8 V) combined with user-defined outputs (0-3.6 V) are said to significantly reduce the number of models required in inventory. Advanced thermal-management techniques facilitate a 0 to 70 www.power-one.com
Power supplies: diagnostics, monitoring
S8VS-Series switching power supplies from Omron Electronics feature built-in diagnostic displays, said to be essential for supporting preventive maintenance programs and shortening troubleshooting time inside control panel. The device’s Smart Display provides operators with at-a-glance status of output voltage, output current, and peak hold current. Depending on model, the display and alarm output indicate the power supply’s remaining service life signaling time for maintenance or replacement, or indicate total run-time of the connected load to alert operations management to schedule parts replacement. International safety standards include UL, cUL, UL508 Listed, and CE. www.omron247.com
Omron Electronics LLC
More comments and more products follow.
Application brief: Linear versus switching power supplies : Responding to the Control Engineering survey on dc power supplies, a validation testing technician at Medallion Instrumentation Systems provides insights on linear and switching power supplies.