Top Hat Rail

What is a top hat rail?

For power supply and control of machines and plants, a large number of electric devices such as power supplies, relays, rectifiers, USV Systems, industrial computers and many others have to be put in the control cabinet, control box or other places depending on its application, set up and environmental circumstances. The top hat rail is best for quick installation and a structured set up. Top hat rails are part of the group of mounting rails. It is different than a C-Rail. Another name for mounting rails is DIN rail. Top hat rails and C-Rails have in common that each of their names derive from the shape of their profile. The top hat rail has a hat shaped profile. Some describe the top hat rail as standard rail.

What is a top hat rail power supply?

The top hat rail power supply is available in many different applications as a switching power supply. This design has a number of advantages compared to a classic set up of a transformer. A top hat rail power supply is lighter and smaller than a conventional power supply. It takes up less space in the control cabinet and has a larger degree of efficiency. A top hat rail power supply can be set up for a large range of incoming voltage. A disadvantage is the EMC conduct because of high frequencies. The much more complex circuit in contrast to a conventional power supply may present a higher fail rate. The top hat rail power supply is available for voltages of 5V, 12,V, 24V and 48V.

The Standard for Top Hat Rails

The standard for mounting rails and its subgroup can be found in DIN EN 60715 VDE 0660-520:2018-07. Standardized variants of the top hat rail are available. TH 15-5,5 describes the smallest top hat rail which is 15mm wide and the brims are 5.5mm high. Therefore the measurements of the top hat rail TH 35-7,5 are: 35mm wide and 7.5 high. The only difference of the top hat rail TH 35-15 is the height of the brims being 15mm. Limit deviations are also mentioned in the standard. Top hat rails are mainly made of steel. Some variants are made of copper and aluminium.

The measurements of devices mounted on the top hat rail are mentioned in another standard. DIN 43880:1988-12 mentions cover and installation dimensions. It has to be taken into account that some devices such as switching power supplies are dependent on the convection in the control cabinet for their cooling. For the constructive design of the control cabinet this is to be taken into account.

Latching Mechanisms in Different Variations

Some parts that are made to be mounted on the top hat rail may have different types of mechanisms for latching. If the housing is made out of plastic one of the two claws which can grab onto the back can be made with a certain amount of flexibility. To take the housing of the top hat rail the claw is levered with a tool. A different type of constructive design is the mounting of a lower claw which can be moved against spring pressure to open it up.

Product Families of the Top Hat Rail

Many manufacturers design whole product families with an identical housing profile to allow all products of to be mounted next to each other and connect them with switches or bridges. A product family can also be designed so that all components can be added together to a unit. One example is a power switch for motor protection which is designed so that additional components like help switches, voltage releases, signalling switches and separator elements can be mounted on the side of it. Mounting on the top hat rail allows a safe and quick process of installation. Mechanical elements such as help releases that access the adjacent component through the housing can press help switches. Top hat rail housings are offered by several manufacturers as an empty housing. Circuit boards, components and plug in connectors can be individually used to equip them.