Comments Off on Power Distribution Units (PDUs) 101
What is power distribution?
Power distribution is facilitated through different pieces of equipment that take the power conditioned by your uninterruptible power supply (UPS) and send it to your electronic components. Power distribution solutions can manage and even control energy consumption, distributing power efficiently to help reduce your operating costs and increase reliability.
Types of PDUs
There are several types of PDUs available but are often classified as either non-intelligent or intelligent.
Non-intelligent PDU
Basic PDUs: typically a power strip that accurately distributes the correct voltage and current to multiple outlets.
Monitored PDUs: visually displays the current electric information, but it can only be viewed locally and lacks remote capabilities.
Intelligent PDU
Metered input PDUs: displays metered power locally and over a secure network. Helps managers avoid overloading circuits and calculate Power usage Effectiveness (PUE).
Metered output PDUs: also displayed locally and over a secure network. Not only does it monitor power usage, but can identify the power consumption at the device, server and rack level.
Switched PDUs: similar features as the Metered output PDUs, while providing the control needed to power on / off switches to specific outlets. It increases remote capabilities and creates power sequencing delays that minimize the risk of inrush currents and allows operators to power off devices that aren’t being used.
Single-phase vs. three-phase PDU
This term describes the number of electrical phases that a PDU receives and transmits. Over the past few years, average power consumption per server or device has rapidly increased. The typical power required at a rack has increased from 2 kilowatts to 12 kilowatts and continues upward.
Cabinet vs. rackmount PDU
PDUs come in two form factors: floor standing / cabinet and rackmount.
A floor standing PDU is a larger, three-phase power distribution unit that comes enclosed in its own cabinet. They’re often used to take incoming power and distribute it to an individual rack or group of racks.
Rack PDUs effectively distribute power to racks where multiple outlets are necessary. Beyond the capabilities of a basic power strip, a rack PDU can be used in 120V, 200-240V environments with a variety of plug and outlet configurations.
PDU checklist:
Number of power outlets needed – every device within your rack will require a power source
Type of sockets needed – most devices are powered from C13 or C19 outlets using plug-in cables, but some PDUs are available with color-coded and locking socket outlets
Phases needed – single and three-phase
Power load needed – include a safety margin of 10-20%
Type of mounting needed – smaller PDUs can be installed horizontally within a 19-inch wide frame, but others with a large number of power outlets may require vertical mounting
First, let’s identify if or why you need to use electrical enclosure gasketing. The function of a gasket is to not only protect electronic components contained in electrical housings from outside elements such as weather, but also to prevent electrical hazards from escaping the unit. The proper gasket will provide a tight seal in both indoor and outdoor enclosure applications, with the ability to withstand the life of the product.
Poor seals and low-quality gaskets can cause damage and serious safety issues. An inefficient design can allow gases and liquids to leak into your devices, it can cause system failures that require time-consuming repairs or even fires that put your facility and employees at risk.
Ensuring proper performance for your enclosure gasketing
Before you make material selections and/or installation options, it’s important to understand your specific application requirements. Most applications need to comply with various ratings such as NEMA, UL and IP or military standards.
Ask the following questions:
Temperature – what temperature range will be required?
Location – will the application be indoor or outdoor?
Flame resistance – will the material require a certain flame rating?
Outgassing – will material outgassing harm the internal components?
Gap spacing – what is the area needed to be filled by the gasket?
Gasket function – what protection will the gasket need to provide? (air, liquid, vibration, EMI shielding)
Additional engineering design considerations:
Protect the gasket – a flange on the door that protects the gasket from a direct pressure blast will diffuse the force and greatly improve the chances of passing a wash down test
Door latching – helps provide a proper means of compressing the gasket
Material selection – ensure the appropriate gasket material is used for your environmental requirements
Gasket rebound – rebound or resistance to taking a compression set can be critical, especially on door gaskets that are being unseated regularly
Functional life – longevity of the gasket will depend on how the material is used: exposure to UV, ozone, temperature, chemicals, and mechanical wear
Venting – pooled water can get sucked into an enclosure during a rain shower from the vacuum affect from cool rain on a hot box
Material selection for your enclosure gaskets
There are a variety of materials to choose from when it comes to providing the perfect seal on an enclosure. Look for an option that is both cost-effective and delivers optimum performance.
Common materials used:
closed cell sponge rubber (neoprene, PVC)
cellular urethane
polyethylene
silicone
Which application process should you utilize?
There are three common types of gaskets:
Foam-in-place – they require a special liquid polyurethane spray to be applied to the edges of the mating, that once dried and hardened can provide a good deal. A downside to this option is that it can easily be damaged and can be a costly application process
Strips – these are typically used as a temporary solution until a better gasket option can be found. It often leaves gaps and leaks.
Custom water jet cut – they can be cut from a variety of materials to the precise size and thickness you need
NEMA / UL 50 Enclosure Gaskets
Technically there aren’t any NEMA gaskets since the enclosure is evaluated as a whole, but there are gaskets and gasket materials that will help an enclosure pass a specified test.
NEMA / UL 50 Type
Description
Common Material Types
Type 1
Basic, indoor enclosures, protects from dust and falling dirt
Open cell or closed cell foams, closed cell sponges
Type 2
Indoor enclosure, protects against dust and falling dirt as well as dripping / light splashing of water
Fine pitched open cell (microsellular) foams or closed cell foams, closed cell sponges
Type 3
Indoor / outdoor enclosure, protects against windblown dust and falling dirt. Also protects against water (rain, sleet, snow and effects of ice formation)
Closed cell foams or closed cell sponges
Type 4
Indoor / outdoor enclosure, protects against windblown dust and falling dirt. Also protects against water (rain, sleet, snow, splashing water and hose directed water and effects of ice formation)
Closed cell foams or closed cell sponges
Type 5
Indoor / outdoor enclosure, protects against falling dirt, settling airborne dust, lint, fibers and flying debris. Also protects against water (rain, sleet, snow, splashing water and hose directed water and effects of ice formation)
Closed cell foams or closed cell sponges
Type 6
Indoor / outdoor enclosure, protects against falling dirt. Also protects against water (hose directed water and the entry of water during prolonged submersion at a limited depth and effects of ice formation)
Indoor enclosure (w/o knockouts, 12K w/ knockouts), protects against falling dirt, settling airborne dust, lint, fibers and flyings. Also protects against water (dripping and light splashing)
Fine pitched open cell (microcelluar) foams or closed cell foams, closed cell sponges
Type 13
Indoor enclosure, protects against falling dirt, settling airborne dust, lint, fibers and flying debris. Also protects against water (dripping and light splashing). Some protection against spraying / splashing / seepage of oil and coolants
Chemical compatible closed cell sponge
IP Enclosure Gaskets
The intentions of the IP code are similar to NEMA and UL. The first digit (IP 6X) refers to solid particle. The second digit (IP X1) refers to water. For example, IP%$ refers to an electronic enclosure capable of sealing out dust, water and protect against vertically dripping water.
IP Spec
1st Digit
2nd Digit
Common Material Types
IP53
5 Protect from dust and water, some dust ingress allowed but not to interfere with function
3 Protect from spraying water (angle up to 60 from vertical)
6 Completely protected from dust and water ingress
7 Protect while temporarily submerged (up to 1 meter)
Solid rubber
EMI Enclosure Gaskets
Commercial applications, not held to military specifications, typically yse nicel graphite filled silicone. The Nickel particles are mixed into silicone polymers and cured into conductive rubber sheets or rolls. Larger EMI gaskets can be made with strips or interlocking strips to maximize the yield.
For gaskets required to meet MIL-DTL-83528, the polymer and conductive fill are defined by specification types:
Type A – silver coated copper + silicone (65 durometer)
Type B – silver coated aluminum + silicone (65 durometer)
Type C – silver coated copper + flurosilicone (75 durometer)
Type D – silver coated aluminum + fluorosilicone (70 durometer)
Type M – silver coated glass + silicone (65 duromater)
Keep your electronics interference-free
At A&J we use a .140 diameter tubular gasket (210-1130) that is added to the extrusion grooves and consists of a silicone inner core that is plated with silver / aluminum for the seams between the frame members that are joined together.
Our enclosures are attenuated to 60 DB from 150 Hz to 1 million Hz and 40 DB from 1-2 million Hz in accordance with MIL-STD-461G for EMI/RFI shielding. Our team of professionals can help you determine the type of shielding your rack or enclosure needs and install it quickly and efficiently.Contact us today!
Configure-to-Order Options
Download our PDF to review A&J Manufacturing standard rack configurations including panel options, doors and RETMA rails.
