Something I often see in smaller control panels is a transformer converting high-voltage down to 120V, which is then fed into a 24VDC power supply. My first question is always this: “Why do you have that transformer, and what is it needed for?” Frequently, it is simply to power the 24VDC supply for control voltage, and nothing else. This is the ideal situation for one of my favorite power supplies – the PSU200M from Siemens.
The PSU200M allows for an input range of 120-230V on single phase and 230-500V on two phase power. It is a single stabilized power supply that will produce 24VDC on most of the worlds’ AC power systems. At the minimum, it combines two items into one – but the benefits are more complex that just that.
Some of the potential benefits of the Siemens PSU200M:
Eliminate the need for Control Transformer simply to power 24VDC supply.
Reduce panel space required.
Reduce weight (5A model ~1.3lbs, 10A model ~1.7lbs).
Consolidate panel designs.
Mounts to DIN rail.
Utilizing a single component for a wide range of voltage inputs can decrease component count in panel and on the shelf when manufacturing for different installations. By mounting onto the DIN rail, a heavy transformer no longer needs to be installed onto the back plate, and on a small panel it helps significantly with weight distribution and center of gravity. Spacing is required top and bottom with the PSU200M, though not on the sides, so when considering panel size reduction, this is an important feature to be aware of. Addressing efficiency is a complicated subject – at lower loads you are compounding inefficiencies sending power through multiple components. Lastly, transformers can radiate a lot of heat as well, which is the natural enemy of electronics.
Recently I had the pleasure of assisting a customer in redesigning their panel and incorporating the PSU200M into their system that was running on 480V. My favorite reaction was the surprise resulting from the system running without a control transformer and no obvious three phase power supply. Working for a high-tech distributor like Axis NJ, it is a joy to be able to introduce products like these to customers.
Control transformers have their place in many applications, and my goal isn’t to convince people to get rid of them everywhere, but there are certainly a lot of applications where the PSU200M is a great fit. And if I haven’t convinced you to at least take a look, we have some pretty great Control Transformers too.
Eric Kozub
APPLICATION ENGINEER