Current Collector
A current collector is a device used to collect electrical current from a moving conductor, such as a train or a trolley. It is typically used in electric vehicles, such as trains and trams, to transfer power from an overhead power source to the vehicle's electric motor.
The current collector consists of a sliding contact, which is often made of carbon or copper, that makes contact with an overhead power source, such as an overhead catenary wire or a third rail. The sliding contact is mounted on the vehicle and is typically in the form of a pantograph or a trolley pole.
The pantograph is a device with a metal frame and a spring-loaded arm that presses against the overhead power source. It is raised and lowered by the operator of the vehicle, and as it moves along the overhead power source it maintains contact and collects the electrical current.
The trolley pole is a vertical pole that is mounted on the roof of the vehicle and has a horizontal arm that extends out from the pole and makes contact with the overhead power source. The pole is typically mounted on a swivel, which allows it to move as the vehicle turns.
The current collector is a critical component in the operation of electric vehicles, as it is responsible for collecting power from the overhead power source and transferring it to the vehicle's electric motor.
Types Of Current Collector
In order to collect the current sparkless, even pressure should be maintained against the trolley wire at all speeds. Three types of collectors are mainly used which are as follows.- The trolley type
- The bow type
- The pantograph type
1. Trolley collector
A trolley collector is used on tramways and trolleybuses and mounted on the roof of the vehicle. Contact with the overhead wire is made by means of either a grooved wheel or a sliding shoe carried at the end of a light trolley pole attached to the top of the vehicle and Held in contact with the overhead wire by means of a spring.Trolley collectors always operate in a trailing position. It is employed up to speeds of about 32 km/h as beyond this speed there's every possibility of the wheel jumping off the trolley wire.
The pole is made to swivel about its support so that it can be reversed for reverse running and rendering it unnecessary for the trolley wire to be accurately maintained above the center of the track.
It enables the bus to manage traffic up to a distance of 3.5 to 4.5m on either side of the contact wire. Although the wheel has a deep groove there is a danger of its jumping off the wire, at points and crossings, at speeds of more than 30 km/hr.
2. Bow collector
It can be employed for a higher speed. It consists of a light metal strip or bow (about 1m long) pressing against trolley wire and the framework is mounted on the roof of the car.The strip is made up of soft material (e.g. Copper, Aluminum, or Carbon). A bow collector also operates in a trailing position. Hence it requires the provision of either duplicate bows or an arrangement for reversing the bow for running in the reverse direction.
It is not suitable for railway work where speeds up to 120 km/h and currents up to 3000A.
3. Pantograph collector
The Pantograph collector maintains the link between the overhead contact wire and the power circuit of the electric locomotive at different speeds under all wind conditions and the stiffness of overhead equipment.This necessity is that positive pressure must be maintained at the least time to avoid loss of contact ad sparking but the pressure must be as low as possible in order that the wear of the overhead contact wire is minimum.
It is mounted on a pentagonal framework which may be raised or lowered by compressed gas or springs. Compressed air for raising is normally used. It is used where vehicles at high speeds i.e. in railways and where currents to be collected are large (2000 to 3000A).
