The ubiquitous nature of components for DIN-rail mounting makes this standard particularly helpful … especially when panel redesigns are in order. Here, a technician need only to unclamp components, slide them to their new locations, and reclamp them to the DIN rail. In addition, DIN rail prevents upside-down and other incorrect installation.
A typical DIN rail in use might accommodate relay sockets, circuit breakers, terminal blocks, fuses — as well as small drives, industrial-communication devices, PLCs, or other controls.
The Deutsches Institut fur Normung (DIN) is a German institute for standardization and a leading provider of technical standards worldwide. It is the organization which has (among other things) established the standard for uniform geometry and electrical connectivity regarding 35-mm DIN rails so ubiquitous in today’s control panels and automation equipment.
Why is DIN rail so ubiquitous?
Well, reconsider the terminal blocks that are detailed in the Design World article Basics of terminal blocks and their various subtypes — a component commonly found mounted onto such DIN rails. Terminal blocks meant for rail mounting are either DIN compliant or proprietary. The latter come in an array of formats, with geometries that are vendor specific — necessitating strict use of only the vendor’s blocks and rail with no possible mixing and matching. In contrast, terminal blocks that comply with DIN requirements are in many instances interchangeable; they also tend to be smaller than proprietary blocks for a given electrical-power rating.
Note: Besides their differing rail and mount geometry, DIN and proprietary systems also have differing electrical connections. For example, DIN-style terminal blocks have a dead-front configuration — with recessed termination hardware in their plastic block housing to isolate electrically live parts … and minimize the risk of shock, even if connections on the block are live. In contrast, some proprietary terminal blocks have open electrical receptacles.
Basic construction and versions of DIN rail
Left: This is how one component (a Siemens 6EP3310-6SB00-0AY0 power supply) mounts onto a standard EN 60715 DIN rail inside a control cabinet. The technician hooks the power supply’s upper mounting geometry onto the rail’s upper edge and presses down to lock the component in place. Removal is simple — requiring that the technician pull up the slider with a screwdriver to disengage the component at the DIN rail’s bottom edge. Then the supply simply unhooks from the DIN rail’s upper edge.
DIN rail is made of straight extruded aluminum or cold-rolled steel tracks that are finished with either chrome or zinc plating. Slots in this rail allow installers to screw or both DIN rail to the inside walls of a control panel or other protected wall. Longitudinal bends in the DIN rail profile serve as shoulders upon which various components can clamp.
Several DIN-rail geometries exist … and in many cases, components for DIN-rail mounting are capable of clamping to a couple different styles of DIN rail.
DIN 1 or C DIN rail — so called for is C-shaped cross section — is for systems rated to 600 V. With a total face width of 35 mm, this is a particularly common variation. This rail’s edges turn inward, so components attach to such rail by clip mechanisms that engage the inside channels of the rail tracks. Note that some technicians nickname component attachments by key dimensions — so a terminal block with hardware to snap onto a 32-mm DIN 1 rail (having a lower lip 22.5-mm deep) may be called a 22.5-mm block for the depth of its lower latching mechanism.
G DIN rail — also called asymmetric rail for its extra bit of lip on one longitudinal edge — is also for systems rated to 600 V. In fact, this type of rail closely resembles C DIN rail … but with its deeper bottom lip, it’s often used to hold particularly heavy components that need more mounting engagement. G-shaped rail for the orderly mounting of components is the oldest rack design, dating back to the 1920s … and predating the first DIN-rail standards by a couple decades.
DIN2 or top-hat DIN rail — also called symmetric rail for the matching longitudinal bends of its brimmed-hat cross-sectional profile — is also for systems rated to 600 V. Its edges flare outward; components attach to such rail by wrapping clip mechanisms around these edges.
Mini DIN rail is for systems rated to 300 V. These are far less common than 35-mm DIN rail variations.
75-mm top-hat rail is yet another option for very large electrical and electronic components.
Download this article (and the rest in this connectivity series) at the Design Guide library.