what is Dc electrification system ?
Answers
Answer:
Hope this will help you
Explanation:
In this type of system, three-phase power received from the power grids is de-escalated to low voltage and converted into DC by the rectifiers and power-electronic converters.
DC Electrification System
The choice of selecting DC electrification system encompasses many advantages, such as space and weight considerations, rapid acceleration and braking of DC electric motors, less cost compared to AC systems, less energy consumption and so on.
In this type of system, three-phase power received from the power grids is de-escalated to low voltage and converted into DC by the rectifiers and power-electronic converters.
DC Traction System
This type of DC supply is supplied to the vehicle through two different ways:
(a). 3rd and 4 the rail system operate at low voltages (600-1200V)
(b).Overhead rail systems use high voltages (1500-3000V)
The supply systems of DC electrification include;
(a).300-500V supply for the special systems like battery systems.
(b).600-1200V for urban railways like tramways and light metro trains.
(c).1500-3000V for suburban and mainline services like light metros and heavy metro trains
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Due to high starting torque and moderate speed control, the DC series motors are extensively employed in the DC traction systems. They provide high torque at low speeds and low torque at high speeds.
Advantages;
1. In case of heavy trains that require frequent and rapid accelerations, DC traction motors are better choice as compared AC motors.
2. DC train consumes less energy compared to AC unit for operating same service conditions.
The equipment in DC traction system is less costly, lighter and more efficient than AC traction system.
3. It causes no electrical interference with nearby communication lines.
Disadvantages;
Expensive substations are required at frequent intervals.
The overhead wire or third rail must be relatively large and heavy.
Voltage goes on decreasing with increase in length.
The supply systems of AC electrification include single, three phase, and composite systems. The Single phase systems consist of 11 to 15 KV supply at 16.7Hz, and 25Hz to facilitate variable speed to AC commutation motors. It uses step down transformer and frequency converters to convert from the high voltages and fixed industrial frequency.
The Single phase 25KV at 50Hz is the most commonly used configuration for AC electrification. It is used for heavy haul systems and main line services since it doesn’t require frequency conversion. This is one of the widely used types of composite systems wherein the supply is converted to DC to drive DC traction motors.