Unit- 5

Synchronous Motor Drives

Q1) Explain BLDC drives with suitable block diagram.

Q2) Design the field coil of a 3 phase, 16 pole, 50 Hz, salient pole alternator, based on the following design information. Diameter of the stator = 1.0 m, gross length of the stator = 0.3 m, section of the pole body = 0.15 m x 0.3 m, height of the pole = 0.15 m, Ampere turns per pole =6500, exciter voltage = 110 volts, Assume missing data suitably.

Q3) The field coils of a salient pole alternator are wound with a single layer winding of bare copper strip 30 mm deep, with a separating insulation of 0.15 mm thick. Determine a suitable winding length, number of turns and thickness of the conductor to develop an mmf of 12000 AT with a potential difference of 5 volts per coil and with a loss of 1200 w/m2 of total coil surface. The mean length of the turn is 1.2 m. The resistivity of copper is 0.021 /m and mm2.

Q4) A 450 volt, 50 Hz, ∆ connected, 4 pole, 3-phase synchronous generator has direct axis reactance of 0.15Ω and quadrature axis reactance of 0.07Ω .Its armature resistance may be neglected. At full load the generator supplies 150A at a power factor of 0.8 lagging.

(a)     Find the internal generated voltage EA of this generator at full load, assuming that it has cylindrical rotor reactance is Xd.

(b)     Find the generated internal voltage EA of this generator at full load assuming that it has a salient pole rotor.

Q5) Write a note on Salient pole wound field motor

Q6) What are the different types of synchronous motors based on the way they are excited? Explain.

Q7) Non-excited motors are available in three designs. What are they?

Q8) Explain closed loop self controlled synchronous motor.