Electric controls: What are they and where are they used?

Electricity is the main responsible for the way of life we ​​have today, from distance communication, development of industries and the emergence of a single world with the internet, and its study is normally divided into 4 major areas, which are generation, transmission, distribution and consumption.
The electrical controls refer to the use of this energy, in the transformation of it as part of a product, constituting techniques and methods for the activation of electrical machines and equipment.
Basically, the electrical controls are divided into two modules/circuits, the power (motors and equipment) where the loads are located, and the command/control which are where the activation and signaling devices are. This load circuit can be single-phase (one phase), two-phase (two phases) or three-phase (three phases), where the amount of electrical charges used represents the total power.

Squirrel cage induction motor.



Known generically as a command button, it works as an element responsible for switching the circuits on and off, the most common being the NO (normally open) and NC (normally closed) type contacts, allowing a large number of configurations. In some, there is a spring return device that, after being activated, returns to its original position (pushbuttons). Other actuators are rotary switches, pedals, limit switches, etc.
In order to facilitate their operation, they have colors defined according to their function according to IEC 73 and VDE 0199 standards, being:

  • red: stop, hang up, emergency.
  • yellow: intervention.
  • green or black: switch on, break, pulse.
  • blue or white: any function other than those mentioned.


The basic mechanism of relays is to turn circuits on and off. The basic circuit used where there is no physical contact between the drive and work terminals allowed the appearance of the modules/circuits mentioned above, in addition to having influenced the concept of the contactors. Most of them perform contact switching through some type of circuit analysis such as the phase-out relays, which identify the lack of a phase and then switch their internal contacts. In general, they are used to relay signals, especially electromechanical ones, which can have one to eight contacts.


It is the main electromechanical device in electrical control, whose predominant function is to control the passage of high currents, also having the NO and NC configurations. They are composed of a coil that produces a magnetic field that provides movement and that in turn performs a change of state of the contacts when energized those that were open when de-energized close and those that were closed open.
They have two types of contact, the power or main contact, which deal with high current generally in blocks of 3 contacts (all NO) for three-phase and auxiliary or command loads (merged between NO and NC contacts according to need), which deal with low current, used for the electrical commands themselves.


They serve to signal the operator of a situation that requires your attention. They can be of the luminous or audible type, the luminous being the most used, presenting as indicators:

  • red: danger, abnormal condition.
  • yellow: attention or care.
  • green: machine released to operate.
  • white: machine in motion, normal operation.
  • blue: any function not previously covered.


These devices are known to the general public because they are present in residential electrical installations, establishments, and cars. Its function is to protect the circuit against shorts and fires, having as characteristics:
– rated current: the current value that the fuse supports without interrupting the circuit.
– breaking current (KA): the maximum current value that the fuse can interrupt.
– short-circuit current: the maximum current value that must be interrupted by the fuse as soon as it is reached.
– rated voltage: is the voltage for which the fuse was developed


It is a device that, like the fuse, serves to protect the circuit from a short circuit or overload, eventually acting as a switch, interrupting the current flow.
The thermomagnetic circuit breakers meet the standard NBR Nm 60947-2 for industrialists and NBR NM 60898 for residential, being this one designed to be used by people not specialized in electricity and not to undergo maintenance.
They also have curves each with its own characteristic.


There are two standards that must be observed when dealing with electrical commands, NR 10 (safety in installations and services in electricity) and NR 12 (safety at work in machinery and equipment).
NR 10 in its definition establishes the minimum requirements and conditions that aim at the implementation of control measures and preventive systems, in order to guarantee the safety and health of workers who, directly or indirectly, interact in electrical installations and services with electricity (10.1 .1).
Among the preventive measures, we can mention the obligation to maintain updated single-line schemes of electrical installations with the grounding specifications, adoption of collective protection measures applicable to the activities developed an adaptation of equipment, devices, and tools that have electrical insulation to the voltages involved.
NR 12 and its annexes define technical references, fundamental principles and protective measures to guarantee the health and physical integrity of workers and establish minimum requirements for the prevention of accidents and illnesses at work in the design and machine use phases and equipment of all types (12.1).
As an example of such measures, we have the devices present in the starting or operating commands of the machines that aim to prevent their automatic operation when energized, the attention when using bi-manual devices to have synchronous actuation, the conformity of the connections and derivations of the electric conductor’s machines to current technical standards in order to ensure mechanical resistance and adequate electrical contact.


As previously mentioned, they are essential in the current world, especially in the industrial area, making it possible to control multiple machines and their activities, optimizing production, reducing prices and avoiding equipment wear. Every day new technologies and other advances appear, from uses in mechatronic engineering to high-powered electric motors, but even with the use of such technologies, we can mention the use of the PLC (developed in 1968), which is essential for electrical controls.
With all this use, it is not surprising to be concerned about the employees who handle them and as their uses expand, new addenda to the current NR can be expected, which are always adapting to new demands and technologies, aiming at a greater harmony of the employed with the work environment, and in this case, man and machine.