Industrial Drive Applications Questions and Answers

Answer: B

In a DC traction system the overhead line or third rail is fed from substations spaced along the track. For suburban lines, where trains run often and draw heavy currents at low voltage (600 V to 1500 V DC), the substations are close together, about 3 km to 5 km apart. The long spacings of 30 km to 50 km or 80 km to 100 km belong to high voltage AC main line electrification, and a spacing of 300 m to 500 m would be uneconomical, since every substation costs rectifiers and switchgear. The answer is option B.

Answer: D

The electronic controller (control unit) of an electric or hybrid vehicle takes in signals from sensors, interfaces them through interface circuitry, and processes them in a microprocessor to give commands to the drive and the battery management. These are its parts.

The power converter (the inverter or DC to DC converter) is the power electronic stage that carries the motor current and is controlled by the controller, but it is a separate unit and not part of the controller itself. The answer is power converter, option D.

Answer: A

A conventional (internal combustion engine) vehicle has a fuel tank holding the fuel, an engine that burns it, and a transmission that carries the engine power to the wheels. So the items are fuel, engine and transmission.

A battery and an electric motor are items of an electric vehicle, and a fuel cell tank belongs to a fuel cell vehicle, so the lists with those items are not conventional vehicles. A conventional car does have a small battery for starting, but the main drive items are those in option A. The answer is option A.

Answer: A

An electric vehicle takes power from the grid through a charger, and the first element of the charger that is connected directly to the AC grid is the rectifier (an AC to DC converter, often with a power factor correction stage). Its DC output then feeds a DC-DC converter or chopper, which adjusts the voltage to suit the battery, and the battery is at the end of the chain. So the rectifier is the one directly on the grid. The answer is option A.

Answer: A

The key gives the boost DC-DC converter as the component used for charging the battery. In the charger the rectified DC voltage is raised to the level that the battery needs by a boost (step up) DC-DC converter, which also shapes the input current in a power factor correction stage.

A DC-AC inverter is used on the drive side to feed the motor, an AC-AC converter has no role in charging a DC battery, and a V/F controlled induction motor is the traction machine, not a charging component. The explanation follows the key, option A.

Answer: D

The methods used to charge an electric vehicle battery are conductive charging (a plug and cable), wireless (inductive) charging through coupled coils, and battery exchange (swapping a discharged battery for a charged one). All of these are in use.

Thermal charging is not a method of charging a vehicle battery, since a battery is charged by an electric current and not by heat. So thermal charging is the one that is not a method. The answer is option D.

Answer: A

Mode 4 is the DC fast charging mode, in which an off board charger supplies DC power to the vehicle. The standard of the International Electrotechnical Commission for conductive charging of electric vehicles, with the modes and the DC charging, is IEC 61851 (its Part 23 covers DC charging stations).

The other numbers (61855, 61888 and 61887) are not the standards for electric vehicle charging. The answer is IEC 61851, option A.