Switchboard equipment: contactors, starters, SPDs and other automation

Recommendation points

• Electric meters
• SPD and lightning protection
• Relays, starters and contactors
• Meters and analyzers
• Signal and control valves
• Additional accessories

You are probably already familiar with the range of circuit breakers and residual current devices, but this is not a complete list of modular devices. In this article we will introduce you to high-level protection and control devices for connecting lines for assembling an electrical panel.

Electric meters

Despite the fact that most of the meters have fasteners for mounting on a DIN rail, only some of them are correctly installed in modular shields. The reason for this is the discrepancy between the height of the device and the dimensions of the DIN standard..

However, the main disadvantage of modular meters is that not all models have an appropriate accuracy class for acceptance by energy sales services. Nevertheless, there are really many varieties of modular meters: single-phase, three-phase, including taking into account the reactive component and generation, digital and pulse-mechanical.

Multi-channel devices are presented as a separate class. They are often 12-14 standard modules wide and are designed for 4-6 outgoing lines. In addition, almost all modular-type metering devices support current transformers. Also, most modern devices are characterized by the presence of a digital module and a port (including wireless) for communication with a PC.

SPD and lightning protection

A rather important class of devices that is not given due attention is protection devices against impulse and ultra-high overvoltages. Standard width of devices – one module for each phase plus one more module for the terminal clamps of the protective conductor.

The principle of operation and purpose of SPDs is a topic for a separate story. It is only important to remember that in a modular design on a 35 mm rail, devices are presented for a rated voltage of up to 1000 V and in four (as a rule) lightning protection classes.

The device of lightning arresters is predominantly tubular, the construction on parallel plates is typical for devices from the expensive segment: ABB, Siemens and Legrand. SPDs of modular type are built on semiconductor elements or on their integrated circuits.

We considered the topic of SPD in detail in the article “Surge protection device. Selection, application, installation scheme “.

Relays, starters and contactors

Contact and contactless switching devices are the most demanded class of devices. Modular contactors, starters and motorized load break switches operate at currents up to 100 A, can be used in both single-phase and three-phase connections. Due to its compact design, switching equipment is very expensive, especially at high ratings of operating currents..

Devices up to 63 A occupy one module per dial-up line. Equipment with a rating closer to the current limit takes 20–40 mm instead of the standard module width. Like the panel-panel mounting technique, modular contactors can be equipped with attachments with additional auxiliary contacts, overcurrent, time limit relays and inrush current compensators. Starters and contactors with a forced mechanical closing button are very common..

Switching equipment has the greatest spread in quality and reliability. Unfortunately, not all manufacturers present prototypes in a transparent case, but a lot can be said by the appearance of the components. The defining parameters of a good contactor will be:

1. Wide silver-plated contact pads.
2. Landing of the main spring and rod guides in metal mandrels.
3. Frequent step of the deionizing grid of the spark arrestor.
4. Coil design, insulation reliability.

All kinds of current relays are very common in modular devices. Often in the DIN standard, only a modular base with an original contact socket is carried out, inside the housing of which there is a routing circuit to the screw terminals. The contact group itself has the form factor of a radio tube and can contain up to 12 (sometimes up to 18) independent pairs of contacts.

Meters and analyzers

A wide range of devices is used to monitor the operating parameters of the power grid: voltmeters, ammeters, power meters. The devices can have both digital and analog operating principles, complex analyzers are quite common, which also keep track of the nominal frequency and control the load on the line. Measuring modular devices have very non-standard dimensions, however, they usually occupy up to 12 modular places in width.

A separate segment of expensive modular equipment is box-type current transformers. Their use is not so widespread, but in the combined control and accounting networks, they allow you to implement very interesting solutions. Information about the current current load can be transmitted including over long distances via a digital channel.

Combined measuring instruments can be quite simple, the size of one standard module, with a simple LCD display to indicate the selected parameter. The simplest example is voltage relays, which are equipped with most modern consumer power grids..

However, there are more complex samples that are capable of simultaneous control over four separate channels of a three-phase network and, sometimes, are capable of switching lines in automatic mode. Naturally, most of such equipment is focused on building AMR systems with a high and medium degree of integration.

Signal and control valves

Sometimes quite complex schemes are assembled in a modular design that require interaction with the user-operator. For example, an installation with a reverse engine start requires at least three buttons and one indicator lamp. Most of this technology is implemented in a modular design..

The range of lamps for mounting on a DIN rail includes products with 10-12 different colors, light sources of different types and brightness. Neon lamps are most common due to their simple wiring and high durability. However, LED products are not inferior in popularity, in addition, such devices can include entire display panels. From multiple lamps in a single housing to multi-line text displays and multi-digit segment displays.

Buttons for modular mounting are also varied. The number of contacts is up to three bipolar, with and without latching, clock and emergency. There are pin-pads and keyboards for specific purposes, and for special tasks – displays with touch control.

Additional accessories

In conclusion, it would be correct to talk about things that simplify the installation and organization of all the mentioned technique. These include, first of all, the screw blocks of zero and protective conductors, the applications of which are countless. To connect current-carrying elements, pass-through terminal blocks and current busbars-combs will be a good help, which allow you to safely and reliably power devices in each row of a modular cabinet.

In general, the range of modular equipment for 35 mm rails can be listed for a very long time: bells, sockets, lighting elements, dimmers, LED strip controllers and thousands of others. It is important to remember that most general-purpose circuits can be assembled in a compact case without installing bulky panel shields that spoil the interior, you just need to take the time to search for components.