As data center power densities continue to rise, the power dynamics of the power distribution units (PDUs) designed to disperse, manage and monitor power within the rack are evolving rapidly to keep pace.

Where 60-63 amp PDUs were once considered high density, according to Calvin Nicholson, senior director of product management at Legrand, the demand for 125 amp PDUs is increasingly becoming the norm.

“The driver is higher kW, and in some cases multiple PDUs are required within the cabinet itself to get to those higher densities on the Alternative Current (AC) side,” explains Nicholson.

A whole new world

With higher densities becoming increasingly common, the industry is now moving towards higher-voltage DC (direct current) architectures – predominantly 800VDC. So, how is this changing the way people think about the evolution of data center power?

Human beings, particularly those operating mission-critical environments, are somewhat risk averse. AC power has been around for a long time – people understand how to use it, where it comes from, how it's distributed, and how to implement it safely. However, once you start talking about DC, it becomes a completely different world, jolting operators from their comfort zones.

“As you start to explore these DC applications, it's all new, and in many cases it's a different cabinet, a busbar in the back, and in some cases a very heavy busbar,” Nicholson remarks. Power shelves also need to convert AC to DC power, which necessitates putting DC power on the busbar while “devices are sliding into the cabinets and taking DC off the busbar itself.”

When it comes to DC architecture, Nicholson highlights Open Compute as a hot button topic, telling us: “We’re now into the ORv3 standard, which has many advantages, such as requiring fewer cables. But the densities are starting to go up into the power shelves, so we’re seeing more interest in Open Compute than ever before.”

Having watched Open Compute since its early inception, Legrand has followed its evolution from past to present:

“With the original Open Compute, we actually provided all the PDUs for a couple years, and then the power shelf design started to come out to the extent that we saw the first shelves. The older standard was an 18kW cabinet or power shelf, but now it’s a 33kW shelf, and they're going to continue to grow from there,” he explains, before remarking that this is a far better fit for the high densities dominating the industry today.

As market interest in Open Compute continued to pique, Legrand responded by going all in, and has been heavily involved for the last two years. “We're developing multiple busbar solutions, multiple power shelf solutions, and we've acquired a cooling company,” he reveals.

This is in addition to the rear door heat exchanger company that Legrand had previously acquired. Add to this a combination of robust T series cabinets and innovative busbars, and Legrand’s ability to bring this all together in a comprehensive system for its customers, which Nicholson says is yielding great results.

Different philosophies

Busbar ratings, says Nicholson, are based on the overall kilowatts of the cabinet. This is checked electrically to make sure it is safe, and they are shipped together. However, there are different philosophies of where to put the power shelves, regarding the redundancies that are held back, and whether an extra shelf should be added.

“On the PDU side it’s a little bit simpler because it’s about how many PDUs can you fit in the cabinet to get the density that you would require,” he explains. Yet this is evolving too. He elaborates that the “next power shelf we’re looking at will be 72kW, and so the densities will continue to go up to support these higher density environments.”

According to Nicholson, customers receive the cabinets, busbars, and power shelves, and then lab-test them. Once they are comfortable with everything and have ensured they meet their application requirements, they implement it in the field.

“It's a much more conservative approach, because there's safety, there's training, and there's all these other things involved that data center operators have to be aware of before starting to go Open Compute,” he stresses. The trouble is, many customers find that their suppliers are chasing hyperscalers instead.

Despite the increased interest in Open Compute, Nicholson attests that one of the more challenging aspects for customers is finding someone to sit down and talk to them about the technology. Thankfully, as an Open Compute trusted advisor, this is where Legrand can offer its support.

“The aim is to take the burden away from customers, making them comfortable with Open Compute solutions – by offering custom designs and new solutions, including cooling. Higher densities mean it can no longer be an afterthought.”

To find out more about the evolution of power hardware for high density environments, check out the full DCD>Talk with Legrand’s Calvin Nicholson, here.