Answer / sai bhargava

Dc machimes are designed like that angle betwean the stator flux and rotor flux is 90 degree to produce unidirectional torque

Answer / umesh

The torque formula for dc motor is T=k(current * flux)
The commutator with brush converts the dc into ac which produces alternating flux.It means both armature current and flux are positive or negative at the same time.

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- two pumps must work with them at the same time but if the first pump start the second pump  must delayed for some time to start  also , with motor rated power = 90 KW and rated voltage = 380 V and rated power factor = 0.85 lag please draw the power and control circuit for it and determine all circuit components parameters that you use it

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1. A 380 / 220 V r.m.s. 3-phase 4-wire circuit carries loads of 8 + j8.1 ohm; 4 + j4.1 ohm; and 2 +j2.1 ohmin the three phases respectively. The length of the circuit is 100 m, and the resistivity of the phase conductors is 0.0005 Ω/m. The neutral conductor is of the same size as the phase conductors. a) Select a reference angle 0for the first phase. Then write down the three phase voltages in both polar format and complex number format. b) Make appropriate assumptions, and take temperature effects on resistance is insignificant. Calculate the currents in the three phases. (Note: Determine conductor resistance, and apply Kirchhoff’s Voltage Law) Based on the result, suggest a main switch rating for the circuit. c) Show your preferred direction of neutral current in a diagram, and then determine its value. (Note: Apply superposition principle, and Kirchhoff’s Current Law) Use its magnitude to show that in this circuit, the unbalanced load may increase the voltage drop in some of the phases. (Note: Also observe the common volt drip in neutral) State your assumptions, if there are any. d) Suddenly the neutral wire of the circuit is broken. Estimate the new currents in the first phase, i.e. Phase L1. State your assumptions, if there are any.

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0 Answers   Orchid,

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how to check regenerative load in drived motor

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