TECHNOLOgy REvIEW > continued
Understanding the choices of power solutions for transportation applications
The LOK4000 series 50W DIN-rail PSUs from Power-One (Melcher) are also nominally AC-DC converters (100-240VAC input) that again feature a DC input (90-250V). Their plastic casing, compact size (see figure 2) and high reliability make them an excellent choice for space-critical applications where DIN-rail mounting is required. The range provides for standard 12V, 24V and 48V outputs with the option to adjust the output voltage using a resistor trim. There are also versions optimised for battery-charging applications (at the same voltages), which can use the trim feature for battery temperature sensing. The LOK4000 PSUs are specified for operation within an ambient temperature range of -10oC to +50o with convection cooling but can operate up to +70oC with derating. They comply with a range of electromagnetic immunity tests for electrostatic discharge and other transient and surge conditions and also meet class B emissions according to EN55022. They also comply with the same shock and vibration standards as the CliQ PSUs and have been safety approved to the relevant worldwide standards. Ingress protection is only provided to IP20 i.e. solid objects (like fingers) >12.5mm with no moisture protection.
various cassette style PSUs. Its Q Series DC-DC converters (see figure 3) are highly rugged units that are particularly suited to railway applications, having been designed in accordance with European railway standards EN50155 and EN50121-3-2. The Q Series offers numerous configurations with six input voltage options (spanning 14.4V – 150V) and single or dual output versions from 3.3V to 24V. Inputs are protected from surges and transients with over- or under-voltage lockout. There is full input to output isolation and outputs are continuously open- and short-circuit proof with front panel status indicators and test sockets. The fully enclosed, black-coated aluminum case acts as both a heat sink and RFI shield and all circuit boards are conformal coated. These cassette-type converters meet the same shock and vibration criteria as the DIN rail PSUs above and Class 1 equipment standards for safety.
Murata-PS has just recently introduced its newly designed Euro-Cassette type DC-DC converters. The UCR100 series are rated from 100W to 132W, providing single output voltages of 5V, 12V and 24V with corresponding currents of 20A, 10A and 5.5A. Like Power-One’s Q Series, the UCR100 units are housed in 3U/4TE size cassettes and are similarly designed to meet the rugged needs of transportation applications over a wide -40oC to +85oC operating temperature range.
box type power supplies
‘Box type’ is a commonly used description for PSU enclosure styles that do not conform to the physical format or mounting requirement styles covered above.
Figure 3: A Power-One (Melcher) Q Series Euro-Cassette DC-DC PSU
Figure 2: Power-One’s LOK-4000 series 50W DIN rail PSU
cAssette type power supplies Cassette-style enclosures are designed for mounting in equipment racks and may be referred to as Euro-Cassette where they comply with the dimensions for European modular 19” DIN-rack systems. Typically these PSUs can also be chassis-mounted with screw fixings. All the examples outlined below are DC-DC converters. Power-One (Melcher) manufactures
www.avnet-abacus.eu
The Power-One (Melcher) HR Series cassette PSUs provide exceptional performance in meeting the EN50155 and EN50121-3-2 railway standards with an extremely wide input voltage range (from 12V to 168V in a single unit), high efficiency (up to 94%) and high reliability with all the usual protection and safety features that we have come to expect from a product designed for transport applications, including conformal coating of the circuit boards. The HR range offers dual outputs at 12V, each rated at either 10A or 12A or single output versions at 12V (20A or 24A) and 24V (10A or 12A). Not surprisingly, given the overall power rating or 240/288W, these units are somewhat larger than the Q series but are still designed for insertion into a 19” equipment rack.
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The B40SR series DC-DC converter from Delta PSU is a good example and features a metal base plate that both facilitates mounting (with four screw holes) and aids heat dissipation (see figure 4). This unit will operate from a wide 18-60V input and delivers a 12.4V output at 24A (i.e. 300W) with a full-load efficiency up to 88.3%. The B40SR series operates over -40oC to +85oC and provides input under-voltage lockout and protection from input reverse polarity, over temperature, short circuits and output over-current / over voltage conditions. One feature though distinguishes this PSU from others we have looked at so far. This is its IP67 rating, which provides complete sealing against dust and immersion in water up to a depth of 1 meter, making it ideally suited for use in dirty outdoor environments.
Figure 4: Delta B40SR series DC-DC converter
The LCC250 is an AC-DC power supply from Emerson Network Power. It has a similar fully enclosed, conduction-cooled construction to the Delta B40SR converter but features wired
focus magazine - issue 15
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