Synchronous Motors

A three-phase Y-connected synchronous motor with a line-to-line voltage of \(440\) V and a synchronous speed of \(900\) rpm operates with a power of \(9\) kW and a lagging power factor of \(0.8\). The synchronous reactance per phase is \(10\) ohms. Determine the torque angle in electrical degrees.

A \(10\)-hp, \(230\)-V, three-phase Y-connected synchronous motor has a reactance of \(3\) ohms per phase and a negligible resistance. To what voltage must the motor be excited in order to deliver full load at unity power factor and \(90\%\) efficiency?

A \(6.6\) kV, Y-connected synchronous motor has a synchronous reactance per phase of \(10\) ohms and a negligible resistance. For a certain load, the motor draws \(990\) kW at normal voltage. At this load, the induced emf per phase is \(5160\) V. Determine operating pf.

A \(75\)-hp, \(600\)-volt, \(1000\)-rpm, three-phase Y-connected synchronous motor has an armature resistance of \(0.05\) ohm per phase and a leakage reactance of \(0.45\) ohm per phase. The efficiency at rated load, \(80\%\) pf leading is \(92\%\). Determine mechanical power developed within the armature.

A \(230\) V, \(60\)-Hz, \(3\)-phase, Y-connected synchronous motor draws a current of \(20\) A and delivers \(8\) bhp. Armature resistance per phase is \(0.5\ \Omega\). If the iron and friction losses amount to \(300\) W, determine the operating power factor of the motor.

A \(2200\) V, \(200\) hp, \(3\)-phase mesh connected synchronous motor is working on full load at an efficiency of \(0.88\) and \(0.8\) power factor leading. The armature reactance per phase is \(5\) ohms. Determine the induced emf per phase. Neglect resistance.

A \(15\)-hp, \(230\) V single-phase synchronous motor is taking a current of \(50\) A at a power factor of \(0.85\) leading. Effective armature resistance is \(0.2\) ohm. If this motor drives a mechanical load of \(12\) hp, determine its rotational losses.

A \(440\)-V, single-phase synchronous motor is drawing a line current of \(50\) A at \(0.9\) pf lagging. This machine has an armature resistance and reactance of \(0.8\) and \(10\) ohms respectively. If stray power and excitation losses amount to \(500\) W and \(800\) W respectively, determine bhp output of the motor.

A three-phase synchronous motor is measured by two A and B wattmeters. It reads \(28.6\) kW and \(46.5\) kW, respectively. The input power of the motor is under excited and assumed constant. What are the readings of A and B wattmeters if the power factor is \(85\%\) and the motor is over-excited?

The input power to a \(600\)-V synchronous motor is measured by means of a two-wattmeter method. One wattmeter reads \(64\) kW and the other reads \(36.5\) kW. The motor is known to be operating at leading pf. Determine the line current drawn.

A 10-hp, 230 v, three-phase Y-connected synchronous motor has a reactance of 3 ohms per phase a negligible resistance. To what voltage must the motor be excited to deliver full-load at unity power factor and 90% efficiency?

The input power to a 600-v synchronous motor is measured by means of a two-method. One wattmeter reads 64 kW and the other reads 36.5 kW. The motor is known to be operating at leading p.f. Determine the line current drawn.

A 500 volts 1 synchronous motor is taking 50 amperes at a p.f. of 0.8 leading. The output is 25 Hp and the effective resistance of the armature is 0.25 ohm. Find the iron and friction losses.

The output of a 200-volt 1 synchronous motor, taking a current of 20 amperes is 4 HP, its effective armature resistance is 0.5 ohm. The iron and friction losses amount to 400 watts. What is the motor power factor?

A 500 volt, single-phase synchronous motor is taking 50 amperes at a p.f. of 0.8 leading. The output is 25 HP and the effective resistance of the armature is 0.25 ohm. Find the iron and friction losses.

A 440-volt single-phase synchronous motor is taking 50 amperes at a pf of 0.9 lagging. The effective resistance of the armature is 0.8 ohm. If the iron and friction losses amount to 600 watts, find the horsepower output.