Electro-Magnetic World: Connection of Auxiliary Energies

The main concentration of work concerning the connection of auxiliary energies (electrics, pneumatics, hydraulics) is on the electrical auxiliary energy. This form of auxiliary energy is the dominant factor in the operation of an automation system.

Picture 1: Principal aspects regarding the connection of electrical auxiliary energy

Because of the different groups of consuming devices, the sequence of connecting different voltage levels is determined and a procedure (steps 1 to 3) introduced as shown in Picture 1, whereby these voltages are made available:

Step 1:

Connection of electrical auxiliary energy for processors (process control system, compact controller, PLC technology and PC’s):

>> Typical voltage levels:
- 230 V AC;
- 24 V DC (made available via power supply units).

Step 2:

Connection of electrical auxiliary energy for automation equipment – standard consuming devices (such as sensors, actuators, measuring transducers and safety devices):

>> Typical voltage levels:
- 230 V AC (main supply);
- 24 V DC (made available via power supply units).

Step 3:

Connection of electrical auxiliary energy for automation equipment – Large consuming devices (such as pumps and heaters):

>> Typical voltage levels:
- 400 V AC (main supply);
- 230 V AC.

Picture 2 to Picture 5 provide examples of this, which represent technically, a typical circuit solution in line with the connection procedure (steps 1 to 3). Picture 2 shows an example of how, by implementing steps 1 to 3, the electrical auxiliary energy for the small-scale experimental module is to be connected. This illustrates that the compact controller (processor) is the first to be supplied with auxiliary energy, followed by the sensors, actuators, small pumps and safety devices and, finally, the heater (being a large consuming) device.

Picture 2: Connection of electrical auxiliary energy using the example of a small-scale experimental module

An individual example then illustrates, which proposed circuit is more favourable for the supply of electrical auxiliary energy for the processors (Picture 3), whereby the safety device as well as the pneumatic auxiliary energy is supplied via the additional contacts of contactors K1 and K2. (Picture 5). Picture 4 demonstrates an example of the connection of electrical auxiliary energy for large consuming devices, whereby the allocated pumps and heaters are supplied with the required 40 V AC via contactors K3 to K6.