AC MACHINES (MOTOR)

25問 • 1年前

問題一覧

A 60-Hz induction motor has two poles and runs at 3510 rpm of the What is the synchronous speed of the induction motor?

3600 rpm

*The rotor of a three-phase, 60 Hz 4-pole inductor motor takes 120 KW at 3 Hz What is the rotor speed of the induction motor

1710 rpm

A three phase induction motor rotates at of 3510 rpm at normal voltage and frequency of 60 Hz What is the motor slip in percent?

2.5%

Determine percent slip of induction motor when rotating at 960 rpm

*Determine the number of poles of induction motor running at 1175 rpm

A 3-phase induction motor is wound for 4 poles and is supplied from a 50 Hz system What is the rotor frequency when rotor runs at 1410 rpm?

3 Hz

The rotor of a 3-phase, 60-Hz, 4-pole induction motor takes 120 kW at 3 Hz Determine the rotor copper losses.

6 kW

A 15 Hp 4 pole 60 Hz, wye connected, 208 volts induction motor draw 12 KW from the line have losses as follows. Stator copper loss 900 W, Rotor copper foss 300W, Iron loss 800W and Friction & Windage Loss 100W Determine the speed of the motor in rpm.

1747

A 5 HP four-pole 60-cycle three-phase induction motor takes 4500watts from the supply. The rotor and stator copper per losses are 92 and 292 watts, respectively The friction and windage losses are 72 watts and the core loss is 225 watts. What is the efficiency?

84.8%

What is the ratio of maximum to full load torque in a motor having slip of 5% at full load and 25% at maximum torque?

2.6

*A 4-pole, 60 Hz 200 V induction motor having a full load current of 350 A. torque developed is 700 N-m. What is the approximate speed of the motor?

955 rpm

A three phase 230 volts, 95% efficiency 76% power factor, 75 hp induction motor draws a starting current 5 times of full load current. What is the starting current?

960 amperes

A 25 Hp. 230 Volts, three-phase motor with 85% efficiency and 75% power factor has a starting current of 5.5 times rated current. To reduce the starting current, a wye-delta starter is installed What is the new starting current?

135 Amp

A 75 HP, 440 Volt 3-phase 10 Amp. 1730 rpm induction has starting current of 8 times the full-load current when started at full voltage. The motor is equipped with an auto transformer or starting compensator if the auto-transformer is set at 65% tap what is the starting line current?

25.4 Amp

A synchronous motor can develop synchronous torque

only at synchronous speed

An under-excited synchronous motor takes

lagging current

A synchronous motor can be used as a synchronous capacitor when it is

over excited

A synchronous motor which works on a leading power factor and does not inve a mechanical load is called as

synchronous condenser

Which of the following motors is non-self starting?

synchronous motor

A 6 pale synchronous motor has a speed of 1174 rpm at certain instant, what is thesupply frequency?

58.7 Hz

A 2300 volts, three phase, wound rotor synchronous motor has Xs 2 ohms per phase and Ras 0 1 per phase The motor operates at 0 866 leading power factor fagging while taking a line current of 350 amperes Find the power angle?

-20.7°

A single phase motor ruris a duty cycle 20kW for 10s, 40 kW for 10s, 60 kW for 5s 80 KW for 10s and idle for 10s What must be the rating of the motor?

47.6 kW

At a certain location in Australia, it is necessary to supply 300 kW of 60 Hz power The only power sources available operate at 50 Hz. It is decided to generate the power by means of a motor-generator set consisting of a synchronous generator How many poles should each of the two machines in order to convert 50 Hz to 60 Hz power?

A 10 pole synchronous motor coupled to a 12 pole synchronous generator

Under which of the following conditions hunting of synchronous motor is likely to occur?

Periodic variation of load

The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as

pull in torque

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premopremo remo · 75問 · 2年前

DC CIRCUITS POWERLINE