AC – DC rectifiers in telecommunications. Part 1

For a better use of this material, we invite you to read the post Power equipment for telecommunications. Part 1. In it we explain in more detail the operation of the AC – DC rectifier.

Initially you should know that the AC – DC rectifiers for telecommunications are responsible for performing the power conversion to bring AC electricity to DC electricity.

The output voltage of the rectifiers for fixed telecommunications is -48 Vdc and for mobile telecommunications is 24 Vdc.

The negative sign is due to the fact that the 0 V or ground point is located at the positive pole of the DC power supply system for fixed telephony.

For mobile telecommunications, the negative pole is the one that is connected to ground, for this reason the DC voltage has a positive sign.

As you can see, the sign of the voltage has a great importance of referential type. This is very relevant when loads are going to be transferred from one system to another, both in DC and by the own characteristics of the equipment.

It is also important to take it into account, because each equipment has its sources designed for the corresponding configuration.

In the post on Grounding systems for telecommunications we will analyze this point in more depth.

Next, I will give you a general idea, as clear as possible, about the basic operation of rectifier equipment.

Operation of AC – DC rectifiers

It is important to highlight that, due to its function, this equipment is essential for the DC power system for telecommunications because of the energy conversion it performs.

The rectifier equipment, in order to work, always requires to be energized with AC electricity.

In the image above, the red lines indicate energization under normal operating conditions with AC power present.

TPE is the Main Emergency Power Panel. We have already talked about this equipment in the post Telecommunication Power Equipment. Part 1 which is already published.

The above implies that when there is some kind of power failure or the power supply goes out of the required parameters, the rectifier equipment shuts down.

As you may already know, the connected loads must not be without power at any time, in order to maintain the service.

So they are fed with DC power through the battery backup system, as shown by the red lines in the following image.

In the article Batteries: all the basics you should know, which we are preparing, we explain how these elements work and their importance.

Capacities of AC – DC rectifiers

There are different capacities of the rectifier equipment, which are defined in Watts according to the voltage level. In this way, the current intensity that can be supplied is established.

Being DC electricity, it is quite simple to know the remaining parameters.  For example, in a DC power system for fixed telecommunications, the voltage level would be 48 Volt. For this example we will only talk about the voltage without taking into account the negative sign.

So if you have a 4800 Watt rectifier, the current it can supply would be 100 Ampere.

This would be only one factor to take into account, since there are others to be considered such as the type of loads, batteries to be connected, and others.

In the Course of design of power systems for telecommunications that we are developing, I explain how to make the selection of rectifiers. You can view the entire content of it here.

There I will teach you everything you should keep in mind to select a type of rectifier by technology and capacity.

Functions of AC – DC rectifiers

The functions of this equipment are as follows:
. – Energize telecommunication equipment and DC/AC inverters through AC to DC power conversion

. – Recharge the battery banks, in float or equalization

These concepts are clarified in the article Batteries: all the basics you need to know that we are writing for you. Here you will learn about these types of battery recharging and when they are used.

In the next article called AC – DC rectifiers in telecommunications. Part 2 we will continue deepening in the subject.

There you will learn about how they are connected and the distribution of DC electricity.
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• energydcac.com