Recent questions and answers in Electrical Machines

Which one of the following options is correct regarding the typical double-squirrel-cage structure used in induction motors?At starting, a larger portion of the rotor cur...

A $220 \mathrm{~V} / 12 \mathrm{~V}$ single-phase transformer is designed for use in India and rated $100$ VA at $50$ Hz. Later, this unit is shipped to the USA where it ...

A balanced three-phase supply is given to a $30 \mathrm{~kW}, 4$-pole, $400 \mathrm{~V}, 50 \mathrm{~Hz}$, wound rotor induction motor with Y-connected stator and rotor w...

The induced emf in a $3.3 \: \mathrm{kV}, 4$ pole, $3$-phase star connected synchronous motor is considered to be equal and in phase with the terminal voltage under no lo...

A $\mathrm{DC}$ series motor with negligible series resistance is running at a certain speed driving a load, where the load torque varies as cube of the speed. The motor ...

A $3$-phase star connected slip ring induction motor has the following parameters referred to the stator:\[R_{s}=3 \Omega, X_{s}=2 \Omega, X_{r}^{\prime}=2 \Omega, R_{r}^...

The following columns present various modes of induction machine operation and the ranges of slip$$\begin{array}{ll} \qquad \qquad\textbf{A} & \qquad \textbf{B} \\ \quad...

The four stator conductors $\left(\mathrm{A}, \mathrm{A}^{\prime}, \mathrm{B}\right.$ and $\left.\mathrm{B}^{\prime}\right)$ of a rotating machine are carrying $\mathrm{D...

A separately excited $\text{DC}$ motor rated $400 \mathrm{~V}, 15 \mathrm{~A}, 1500\mathrm{~ RPM}$ drives a constant torqueload at rated speed operating from $400 \mathrm...

A three phase $415 \mathrm{~V}, 50 \mathrm{~Hz}, \text { 6-pole, } 960 \text { RPM, 4 HP}$ squirrel cage induction motor drives a constant torque load at rated speed oper...

When the winding $\text{c-d}$ of the single-phase, $50 \mathrm{~Hz},$ two winding transformer is supplied from an $\mathrm{AC}$ current source of frequency $50 \mathrm{~H...

The frequencies of the stator and rotor currents flowing in a three-phase $8$-pole induction motor are $40\:Hz$ and $1\:Hz$, respectively. The motor speed, in $\text{rpm}...

A $280 \;V$, separately excited $\text{DC}$ motor with armature resistance of $1\:\Omega$ and constant field excitation drives a load. The load torque is proportional to ...

A star-connected $3$-phase, $400\; V$, $50$ $\text{ kVA}$, $50\; Hz$ synchronous motor has a synchronous reactance of $1$ $\text{ohm}$ per phase with negligible armature ...

Consider the table given:$\begin{array}{|cl|cI|cI|}\hline&\textbf{Constructional feature} & \textbf{Machine type} & \textbf{Mitigation} \\ \hline &\text{P. Damper bars} ...

The power input to a $\text{500 V, 50 Hz, 6-pole, 3-phase}$ induction motor running at $975 \text{RPM}$ is $40 \text{ kW}$ . The total stator losses are $1 \text{ kW}$. I...

​​​​​​​In a single-phase transformer, the total iron loss is $2500\:W$ at nominal voltage of $440\:V$ and frequency $50\:Hz$. The total iron loss is $850\:W$ at $220\:V$ ...

A belt-driven $\text{DC}$ shunt generator running at $300\: \text{RPM}$ delivers $100 \:\text{kW}$ to a $200 \:V\: \text{DC}$ grid. It continues to run as a motor when th...

An air-core radio-frequency transformer as shown has a primary winding and a secondary winding. The mutual inductance $M$ between the windings of the transformer is _____...

A three-phase cylindrical rotor synchronous generator has a synchronous reactance $X_{s}$ and a negligible armature resistance. The magnitude of per phase terminal voltag...

A single-phase, $\text{4 kVA}$, $200\: V/100 \: V$, $50 \: Hz$ transformer with laminated $\text{CRGO}$ steel core has rated no-load loss of $450 \: W$. When the high-vo...

The figure below shows the per-phase Open Circuit Characteristics (measured in $\text{V}$) and Short Circuit Characteristics (measured in $\text{A}$) of a $14 \: kVA$, $4...

A $5kVA, 50V/100V,$ single-phase transformer has a secondary terminal voltage of $95V$ when loaded. The regulation of the transformer is$4.5\%$$9\%$$5\%$$1\%$

The parameter of an equivalent circuit of a three-phase induction motor affected by reducing the rms value of the supply voltage at the rated frequency isrotor resistance...

A three-phase synchronous motor draws $200 A$ from the line at unity power factor at rated load. Considering the same line voltage and load, the line current at a power f...

A $220$ V DC shunt motor takes $3$ A at no-load. It draws $25$ A when running at full-load at $1500$ rpm. The armature and shunt resistance are $0.5 \: \Omega$ and $220 \...

A delta-connected, $3.7$ kW, $400$ V(line), three-phase, $4$-pole, $50$-Hz squirrel-cage induction moor has the following equivalent circuit parameters per phase referred...