Product category:
Power Supplies and Uninterruptible Power Supplies
News Release from: Puls UK | Subject: SL10.300 power supply
Edited by the Engineeringtalk Editorial
Team on 05 December 2001
Power unit integrates primary and
secondary fuses
Power supply specialist Puls has launched a three-phase, extremely compact 240W standard power unit which needs no fuses on the primary or secondary side and provides for unrestricted two phase use
Overload behaviour has been one of the focal points of developments by PULS for a number of years It was actually three years ago that Puls initiated the current trend which is moving away from the Hiccup mode to continuous current in the event of an overload
This article was originally published on Engineeringtalk on 10 Nov 2000 at 8.00am (UK)
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The Munich-based firm recognised that the Hiccup mode, in which the power unit temporarily switches off and then attempts a restart at regular intervals every couple of seconds, poses problems in practice: the current surges that occur during the attempted restarts create an unnecessary load on the connected consumers; even more; in drive units they represent a potential injury hazard.
Secondly, the short current surges are insufficient to trigger a secondary fuse.
And specific loads such as motors, high capacities or the DC/DC converters which have recently become increasingly more popular, require a significantly oversized power unit with Hiccup response to start them.
These loads quickly consume twice or more their nominal current for start-up.
If the power unit size is geared to the nominal current it is subject to an overload when starting up and normally switches off immediately, consequently these type of loads do not actually get going.
Further reading
Power supply saves space on the DIN rail
The 80W Puls Dimension QS3 DIN-rail power supply is part of a family of products with output power from 80 to 500W.
PSUs gain UL1604 hazardous location approval
Ten models of the popular MiniLine power supplies family as well as the MiniLine decoupling module have been approved to meet the UL1604 safety standard.
Three-phase switcher puts 48V the rail
The SilverLine series now includes the SL10.305, a 240W, three-phase DIN rail switch mode power supply with an output voltage rating of 48-52V and an output current rating of 5A.
That is why the company introduced the Puls-Overload-Design in 1998: in the event of an overload the power unit delivers up to 1.5 - 1.8 times its nominal current, with the output voltage being reduced as the current increases.
This enables even heavy loads to be started-up without the need for costly, oversized units and, if necessary, the user can employ a secondary fuse in order to securely switch off the load in the event of an overload - a response which was met with enthusiasm by users.
With the SL10.300 Puls is now meeting the demands of users to even greater effect: the overload behaviour can be switched to the so-called Fuse mode via a jumper which is externally accessible: here, in the event of an overload - i.e if the nominal output voltage can no longer be sustained - the unit switches off the output completely after approx.
5 s and displays this status by way of a flashing LED.
To reactivate the output either the Reset button on the front of the unit has to be pressed or the unit separated from the power supply for about one minute (the delay time is created by the fact that after separation from the power supply the internal Elkos first have to be run down).
Thanks to this Fuse mode many users now no longer need the secondary fuse - particularly since the electronic fuse operates with considerably greater precision and is therefore easier to calculate (and more reliable) than the standard thermo-magnetic automatic fuses.
An additional secondary fuse is only required if the shut-off threshold of approx.
12.5 A or 14 A (at 28 or 24 V and 25C ambient temperature) is too high for the connected loads or the overload cut-off after 5 s occurs too late.
This 5 s delay was selected so that the power unit can also cope with the above mentioned slower loads which occur quite frequently particularly in the DIN rail area.
Moreover, this perfectly corresponds with the delay that also occurs in automatic fuses (and in this context widely disperses): it is only when the current reaches more than 2-3 times the fuse value through an automatic fuse with the fast Z characteristic, that it is actually triggered in fractions of a second.
The SL10.300 is also internally fused on the primary side - a rare feature in three-phase units.
This means that the unit no longer needs any external fuse on the primary side, this may only be necessary in order to protect the power supply cable or for other parallel loads if these do not have any internal fuses.
The input has another new feature which has a significant practical importance: in addition to the three-phase operation, two-phase operation is also fully specified, i.e for the very first time a standard power unit also provides for continuous, unrestricted two-phase operation under full load.
In addition, during test measurements the unit demonstrated an unusual tolerance of power supply fluctuations and phase shifts between the three phases when used in problematic networks.
Where other units fail, perhaps because the phase shift causes the voltage between two input terminals to exceed or fall below the specific limits, the Puls unit continues working without a care.
This makes it particularly ideal as an export product e.g to East European countries which frequently have to cope with quite "unpredictable" networks - a '4x4' power unit with all-wheel drive as it were.
Form the viewpoint of minimising the strain on the equipment components, three-phase operation is undoubtedly preferable to two-phase operation although two-phase operation offers an attractive application alternative: the only two input cables on the SL10.300 in this case are fused via two elements of a three-phase automatic fuse, the individual automatic fuses of which are mechanically connected via a transverse rail (see Diagram 2).
The third element of the automatic device is used in the power unit's secondary circuit, with the power unit being operated in continuous current mode (in other words not in fuse mode).
If the overload continues in the secondary circuit this element is triggered and shuts off the other two elements via the mechanical link; this means that the entire product, including any other consumer units connected in parallel, is disconnected completely from the power supply.
With its 250 W output capacity, the SL10.300 is positioned in the medium output range.
It therefore lends itself for use as an all-rounder, "i.e covering the standard applications" and can be easily integrated wherever required - thanks not least to its compact design (WxHxD=89x124x117 mm) and what is undoubtedly the most comprehensive package of licenses on the market (including, amongst others, the CB Scheme!).
However, Puls realised that customers are also increasingly using more units in one and the same system, whether as a decentralised power supply or in parallel mode in order to increase output.
It's in parallel mode in particular that the SL10.300 once again demonstrates strengths which are a rarity in this output category.
As such, the characteristic curve can be switched to be slightly "softer" (1 V voltage difference between no load and full load) which ensures that all power units switched in parallel evenly distribute the load between them.
In addition, in the event of minimal capacity utilisation - lower than normal - the power units do not go into so-called Sleep mode, i.e the control electronics also remain fully active with no load.
The advantage of this can be seen if there is a sudden load surge: where other units first have to be 'awoken' from Sleep mode and leave the load 'in the lurch' for a specific period (or as a result of a mutual overload even deactivate each other on a reciprocal basis) each SL10.300 temporarily takes up its share of the load in the parallel grouping so that even this kind of load surge is evened out immediately and smoothly.
Up to five SL10.300's can be connected in parallel in this way, which means that - thanks to the unique versatility of the unit - virtually every type of application between 0 and 1250 W throughout the world can be provided with a reliable power supply for years with believe it or not just one single power unit model held in stock.
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