Why is an Aircraft DC Generator Operated in Parallel?

The practice of paralleling DC generators, especially in aircraft, enhances reliability, load sharing, and power capacity. This strategy involves connecting two or more generators to operate in parallel, ensuring that the electrical system meets the demand and remains operational even if one generator fails. Here, we explore the reasons and benefits of parallel operation in DC generators.

Key Reasons for Parallel Operation

1. Redundancy and Reliability: Paralleling DC generators enhances the reliability of the electrical system by providing redundancy. If one generator fails, the other generators can take over, ensuring a continuous power supply without interruption.
2. Balanced Load Distribution: By paralleling generators, the overall weight and load distribution among the engines is balanced, reducing the load on individual generators and improving their efficiency. This is particularly important in aircraft, where minimizing the weight and maximizing the efficiency of each engine is critical.
3. Economical and Flexible Operation: Using multiple smaller DC generators in parallel can be more economical and flexible than operating a single, more powerful generator. This approach allows for scaling up or down based on the current power requirements and future needs, avoiding the need for large, excessively powerful single units that may not be fully utilized during normal operations.

The Necessity of Parallel Operation

Parallel operation ensures that multiple generators can share the load, making the system more robust. In practical scenarios, a single generator may not be sufficient to power all the electrical appliances in an aircraft or any other large-scale power distribution system. Utilizing multiple generators in parallel allows for a more balanced and efficient distribution of electrical load.

Practical Aspects of Parallel Operation in DC Generators

Unlike AC generators, DC generators do not require synchronization based on phase angle. However, it is crucial to ensure that all generators in a parallel system operate at the same speed, have the same field excitation, and produce the same voltage. This synchronization ensures that the generators operate in harmony, preventing any one generator from being overburdened or underutilized.

When DC generators are connected to a grid and supplying power to a common busbar, each generator must generate the same voltage. If the generators do not follow this principle, one generator may produce a higher voltage while the other produces a lower voltage. This can cause current to flow between the generators, with the generator producing the lower voltage behaving as a load on the line. This situation should be avoided, and all generators must operate in unison to ensure a stable and reliable power supply.

Benefits and Purposes of Parallel Operation

The main purposes of parallel operation are:

To share the load among the generators if the load increases. This equal distribution prevents any single generator from being overburdened. To provide a seamless transition in case any one of the generators fails. The remaining generators can take over without interruption, ensuring continuous power supply. To allow for future scalability by increasing the total power capacity through additional parallel generators as the need arises.

In conclusion, the parallel operation of DC generators is essential for enhancing reliability, ensuring balanced load distribution, and achieving greater power capacity. This method is widely used in various applications, including aircraft, where the robustness and dependability of the electrical system are paramount.