10 March 2011

Control Systems Interview Questions Answers

Electrical Question: What is a System?

Answer: When a number of elements or components are connected in a sequence to perform a specific function, the group of elements that all constitute a System

Electrical Question: What is Control System?

Answer: In a System the output and inputs are interrelated in such a manner that the output quantity or variable is controlled by input quantity, then such a system is called Control System.
The output quantity is called controlled variable or response and the input quantity is called command signal or excitation.

Electrical Question: What are different types of Control Systems?

Answer: Two major types of Control Systems are 1) Open loop Control System 2) Closed Loop Control Systems

Open loop Control Systems:

The Open loop Control System is one in which the Output Quantity has no effect on the Input Quantity. No feedback is present from the output quantity to the input quantity for correction.

Closed Loop Control System:

The Closed loop Control System is one in which the feedback is provided from the Output quantity to the input quantity for the correction so as to maintain the desired output of the system.

Electrical Question: What is a feedback in Control System? 

Answer: The Feedback in Control System in one in which the output is sampled and proportional signal is fed back to the input for automatic correction of the error ( any change in desired output) for futher processing to get back the desired output.

Electrical Question: Why Negative Feedback is preferred in the Control System?

Answer: The role of Feedback in control system is to take the sampled output back to the input and compare output signal with input signal for error ( deviation from the desired result). 
Negative Feedback results in the better stability of the system and rejects any disturbance signals and is less sensitive to the parameter variations. Hence in control systems negative feedback is considered.

Electrical Question: What is the effect of positive feedback on stability of the system?

Answer: Positive feedback is not used generally in the control system because it increases the error signal and drives the system to instability. But positive feedbacks are used in minor loop control systems to amplify certain internal signals and parameters

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