List of top Electrical and Electronic Measurements Questions on Current asked in GATE EE

A single-phase full-controlled thyristor converter bridge is used for regenerative braking of a separately excited DC motor with the following specifications: 

• Rated armature voltage = 210 V
• Rated armature current = 10 A
• Rated speed = 1200 rpm
• Armature resistance = 1 Ω
• Input to the converter bridge = 240 V at 50 Hz

Assume that the motor is running at 600 rpm and the armature terminals are suitably reversed for regenerative braking.

If the armature current of the motor is to be maintained at the rated value, the triggering angle of the converter bridge (in degrees) should be ____________ (rounded off to two decimal places).

Motor and converter parameters: 

The armature of the DC motor is fed from the full-controlled bridge, and the field current is maintained constant.

A difference amplifier is shown in the figure. Assume the op-amp to be ideal. The CMRR (in dB) of the difference amplifier is (rounded off to 2 decimal places).
 

In the given circuit, the diodes are ideal. The current \( I \) through the diode \( D_1 \) in milliamperes is (rounded off to two decimal places).
 

Consider the stable closed-loop system shown in the figure. The magnitude and phase values of the frequency response of \( G(s) \) are given in the table below. The value of the gain \( K_I \; (>0) \) required for a 50° phase margin is __________ (rounded off to two decimal places). 

Frequency response data of \( G(s) \): 

System diagram:

Consider the stable closed-loop system shown in the figure. The asymptotic Bode magnitude plot of \( G(s) \) has a constant slope of \( -20 \, \text{dB/decade} \) at least till \( 100 \, \text{rad/sec} \) with the gain crossover frequency being \( 10 \, \text{rad/sec} \). The asymptotic Bode phase plot remains constant at \( -90^\circ \) at least till \( \omega = 10 \, \text{rad/sec} \). The steady-state error of the closed-loop system for a unit ramp input is (rounded off to 2 decimal places).

 

Consider the closed-loop system shown in the figure with \[ G(s) = \frac{K(s^2 - 2s + 2)}{s^2 + 2s + 5}. \] The root locus for the closed-loop system is to be drawn for \( 0 \leq KLt;\infty \). The angle of departure (between \( 0^\circ \) and \( 360^\circ \)) of the root locus branch drawn from the pole \( (-1 + j2) \), in degrees, is (rounded off to the nearest integer).

A 5 kW, 220 V DC shunt motor has \( 0.5 \, \Omega \) armature resistance including brushes. The motor draws a no-load current of \( 3 \, A \). The field current is constant at \( 1 \, A \). Assuming that the core and rotational losses are constant and independent of the load, the current (in amperes) drawn by the motor while delivering the rated load, for the best possible efficiency, is (rounded off to 2 decimal places).