Transformers in electric trains?

[cabellos]

I have an exam on monday and looking through the past papers I came across a question I couldn't find a suitable answer to:

List the economical advantages of using a transformer in a train rather than run the overhead lines at 400V?

any help would be very much appreciated...

Phil N

 

[Astronuc]

Well very simply, overhead lines carry electrical current long distances and since Power = Current * Voltage (for AC it's an integral of I(t)*V(t), but essentially the same principle), the current is reduced as voltage increases.

So to minimize power resistive (I²R) and reactive losses, high voltage is used. In the transformer the high voltage is reduced (dropped down) to a voltage suitable for a motor.

 

[ravenprp]

.

Using a transformer in electric trains has several economical advantages compared to running overhead lines at 400V. Here are some possible reasons:

1. Reduced cost of infrastructure: Installing overhead lines at 400V requires a significant amount of infrastructure, including poles, wires, and insulators. This can be costly, especially if the train route is long or complex. On the other hand, using a transformer allows for a simpler and more compact infrastructure, as the transformer can be placed inside the train or at a nearby substation.

2. Lower maintenance costs: Overhead lines are constantly exposed to environmental factors such as weather, which can cause wear and tear over time. This requires regular maintenance and repairs, which can be expensive. In contrast, transformers are generally more durable and require less frequent maintenance, resulting in lower maintenance costs.

3. Improved efficiency: Transformers can step up the voltage from the power source to a higher level, reducing the amount of current needed to power the train. This results in less energy loss during transmission, making the system more efficient. Additionally, transformers can also step down the voltage for use in various systems within the train, further improving efficiency.

4. Flexibility in power sources: With a transformer, the train can be powered by different types of power sources, such as overhead lines, third rail, or battery power. This allows for more flexibility in terms of energy sources and can potentially lead to cost savings, as different power sources may have varying costs.

5. Reduced risk of power outages: Overhead lines are susceptible to disruptions, such as weather events or accidents, which can lead to power outages. Using a transformer, the train can still operate even if the power source is temporarily unavailable, reducing the risk of service disruptions and potential economic losses.

In summary, using a transformer in electric trains can result in cost savings in terms of infrastructure, maintenance, and energy efficiency, as well as provide flexibility and reliability in power sources. These economical advantages make transformers a beneficial choice for powering trains.