In phase control and Integral cycle control the supply voltage is ac and the armature voltage is rectified ac, where as in chopper control the supply is dc and the average armature voltage is proportional to the duty ratio of the chopper. The chopper system is used for dc traction & battery operated vehicle - Choppers using thyristors are more complicated than the phase control system. This is because an auxiliary commutation arrangement is necessary for choppers, whereas commutation is natural owing to a.c. supply in phase control or integral cycle control. Read the paragraph carefully and answer the question based on it.
In one quadrant converters such as half controlled bridge circuit or single phase circuit with fly wheel diodes for DC moter.
Average output voltage is always positive
To solve this problem, we need to understand the operation of one quadrant converters, particularly in the context of DC motor drives. One quadrant converters, such as half-controlled bridge circuits or single-phase circuits with flywheel diodes, are designed to operate in a single direction of current and voltage. Here’s the detailed explanation:
- In power electronics, one quadrant operation typically refers to a circuit that allows current and voltage to be positive, meaning power flows in one direction only.
- The average output voltage being positive means that the current direction and the power flow are both positive, aligning with the motor's natural operation to drive a load in one direction.
- In these converters, diodes are used to free-wheel the current when the controlled devices (like Thyristors) are not conducting. This ensures that the current remains continuous and the motor continues to receive power, although at a reduced level.
- The other options can be analyzed as follows:
- “Average output voltage is always negative” is incorrect because the operation in one quadrant only allows positive voltage and current.
- “Torque is always negative” is incorrect because, with positive average voltage and current, the motor will produce positive torque in one quadrant operation.
- “Regeneration is always possible” is incorrect because, in one quadrant converters, regeneration (where the motor acts as a generator and sends power back to the source) is not possible, as the operation is limited to one quadrant.
- Hence, the most appropriate and correct answer is: "Average output voltage is always positive". This ensures the motor operates in a forward direction, providing positive torque.
Therefore, the correct answer to the question is: Average output voltage is always positive.
Similar Questions
For the circuit given, phase voltage is Vm sin ωmt, where Vm is the peak phase voltage. The value of maximum average output voltage that occurs at a delay angle α = 0 is given by :
The above circuit is operated at 120 V – 60 Hz supply and the load resistance R = 20 Ω, L = 40 mH, delay angles are α1 = 60°, α2 = 120°. The value of :
(A) Peak circulating current = 11.250 A
(B) Peak circulating current = 6.250 A
(C) Peak current of converter 1 = 8.485 A
(D) Peak current of converter 1 = 19.735 AChoose the most appropriate answer from the options given below :
In a two quadrant single phase SCR Drive armature current becomes continuous when :
The reading of an ac ammeter connected to a half controlled rectifier with firing angle α = 0 will be :
In a fully controlled three phase bridge without fly wheel operation the displacement factor and power factor is :
Important Questions from Phase Controlled Rectifiers
- Which of the following is control element in Silicon Controlled Resistor (SCR)?
A 240 V single-phase AC supply is fed to a load resistor of 100 Ω through a thyristor. If the thyristor is fired at 90°, what is the power consumed by the load?
The maximum firing angle that can be obtained by a pure resistive trigger circuit used in phase control circuit is:
The frequency of the 7th harmonic for the fundamental frequency of 50 Hz is:
In a 3-phase converter circuit, during commutation when one SCR in one phase is turned on, turning of an SCR in another phase results is:
