Table of Contents
What is XD and XQ in slip test?
𝑋𝑑=𝑎𝑏𝑐𝑑 After one-quarter of slip cycle the peak armature wave is in line with the quadrature axis. In this position, the reluctance offered by the larger air gap is maximum as shown in Figure-3. Due to the high reluctance, a large magnetising current is required to produce the same air gap flux.
Which is more XD or XQ?
The value of Xad is always greater than Xaq. As the EMF induced by a given MMF acting on the direct axis is smaller than for the quadrature axis due to its higher reluctance. The armature current is divided into two components; one is the phase with the excitation voltage Ef and the other is in phase quadrature to it.
What is d and q axis?
The d axis, also known as the direct axis, is the axis by which flux is produced by the field winding. The q axis, or the quadrature axis is the axis on which torque is produced. By convention, the quadrature axis always will lead the direct axis electrically by 90 deg.
What are the normal values of XQ XD for the two types of SYN machines?
Explanation: Xd=V(max)/I(min) = 30/5 = 6 ohms; Xq=V(min)/I(max) = 25/10 = 2.5 ohms.
What is XD in alternator?
it can observed that rotor field is aligned with the armature m.m.f., its flux linkage are maximum, but the rate of change of flux is zero. Hence voltage induced in field goes through zero at this instant. This is the position where alternator offers reactance Xd.
What is mean by direct axis and quadrature axis?
In Figure-1, the axis shown along the axis of the rotor is known as direct axis or d-axis and the axis perpendicular to the d-axis is called quadrature axis or q-axis. It can be seen that the two small air-gaps are involved in the path of d-axis flux (𝜑𝑑), thus the reluctance of the path is minimum.
What is saliency in motor?
Saliency: the variation of the inductance at the motor terminal according to the rotor position. Also referred to as inductance saliency or magnetic saliency. Permeability: A measure of how easily a magnetic field flows through a material.
What is ID and IQ currents?
The iq current is nominally the torque producing current, while the id current results in a radial force (which happens to be the default state of stepper and gimbal motors).
What is salient pole and non salient pole?
Based on the construction the rotor of an electrical machine is classified into two types. They are, Salient pole type or projected pole type rotor ( low speed, more number of poles, kaplan turbines ) Non-salient type or smooth cylindrical type rotor ( high speed, 2 or 4 poles, pelton wheel )
What is quadrature axis Subtransient reactance?
Quadrature axis subtransient reactance,Xq″ This also is defined in a manner similar to Xd″, but in this case, armature currents are applied in such time phase that the peak of varying armature m.m.f. wave is along the quadrature axis.
What is Subtransient reactance?
Subtransient reactance is the reactance of the motor during the first cycle of the short-circuit. Transient reactance is the reactance of the motor during the remainder of the short-circuit. The computer program supplies typical values of subtransient and transient reactance for motors.
Why does OCC look like BH curve?
However, as the flux density increases, the poles get saturated and the ɸ becomes practically constant. Thus, even we increase the If further, ɸ remains constant and hence, Eg also remains constant. Hence, the O.C.C. curve looks like the B-H characteristic.
Why do you conduct slip test?
Direct and quadrature axis reactance can be determined by this test. During this test, the synchronous machine is driven by the separate prime mover at slightly different from synchronous speed. The field winding is open-circuited and rated frequency and reduced voltage is applied across the terminal.
What is hunting in synchronous motor?
Hunting is the phenomenon of oscillation of the rotor about its steady state position or equilibrium state in a synchronous motor. Hence, hunting means a momentary fluctuation in the rotor speed of a synchronous motor.
What is a 3 phase synchronous motor?
A 3-phase synchronous motor is a 3-phase synchronous machine which is operated as a motor i.e. converts electrical energy input into mechanical energy output.
Is a synchronous motor AC or DC?
A synchronous electric motor is an AC electric motor in which, at steady state, the rotation of the shaft is synchronized with the frequency of the supply current; the rotation period is exactly equal to an integral number of AC cycles.
What is DC synchronous motor?
A synchronous motor is one in which the rotor turns at the same speed as the rotating magnetic field in the stator. Step motors, dc brushless, variable reluctance motors, switched reluctance and hysteresis motors, and dc brush motors all typically operate as synchronous motors.
What is EMF equation of alternator?
f = PN / 120 or N= 120f / P. Putting the value of N in Equation (i), we get, Average value of EMF per conductor = ∴ (N= 120f/P) If there are Z conductors in series per phase, then synchronous generator average E.M.F per phase = 2 f Φ Z Volts = 4 f ΦT Volts ….. (
Is the angle between stator direct axis and quadrature axis?
1. What is the angle between stator direct axis and quadrature axis? Explanation: In reluctance motor, direct axis is horizontal axis and quadrature axis is at 90° to the direct axis. Explanation: Space angle is measured between stator direct axis and long rotor axis.
Which bank does direct axis use?
DirectAxis administers loans for FirstRand Bank Limited, an authorised Financial Services and Credit Provider, and has been providing loans to South Africans for over 20 years. Loan repayment terms range from a minimum of 24 to a maximum of 72 months.
What is pilot exciter?
Pilot exciter: A pilot exciter is a small AC generator with a permanent magnet mounted on the rotor shaft and the three phase winding on the stator. It provides the field current of the exciter. The exciter supplies the field current of the main machine.
What is the use of damper winding?
Functions of Damper Windings:
Damper windings helps the synchronous motor to start on its own (self starting machine) by providing starting torque. By providing damper windings in the rotor of synchronous motor “Hunting of machine”can be suppressed.
How many types of rotors are there?
The four different rotor types are: Blank & Smooth - Blank and smooth rotors are what you'll find on most passenger vehicles and feature a smooth, blank metal surface all the way around the rotor. Drilled - Drilled rotors feature drilled holes around the metal surface.
What is saliency ratio?
"saliency ratio" = Ld / L
The d-axis is when the rotor is aligned with the poles. It is also the orientation with highest inductance. The q-axis is when the rotor is aligned with the gaps. It has the lowest inductance. It can be shown that reluctance motors work best when you maximize the saliency ratio.
What do you mean by saliency?
saliency - the state of being salient. salience, strikingness. prominence - the state of being prominent: widely known or eminent. conspicuousness - the state of being conspicuous. visibility, profile - degree of exposure to public notice; "that candidate does not have sufficient visibility to win an election"
What is double saliency?
So along the top row of the diagram, 1 has no saliency; 2 has a salient-pole stator and a non-salient-pole rotor; 3 has a salient-pole rotor and a non-salient-pole stator; and 4 has what we call “double saliency”, or we say it is “doubly salient”.
What is ID IQ motor control?
Id, iq and the reference values for each generate error signals. The id reference controls rotormagnetizing flux while the iq reference governs motor torque output. These error signals are fed to proportional-integral (PI) controllers whose outputs are sent to the motor as voltage vectors Vd and Vq.
What is projected pole type?
The projected poles are made up from laminations of steel. The rotor winding is provided on these poles and it is supported by pole shoes. Salient pole rotors have large diameter and shorter axial length. They are generally used in lower speed electrical machines, say 100 RPM to 1500 RPM.
What are the differences between salient pole and non-salient pole type alternator?
Non-Salient pole Synchronous Alternator:
Non-Salient pole generators will have smaller diameter and longer axial length. They are used for High speed operation (typically speed will be 1500 and 3000 rpm) Better in dynamic balancing because of absence of salient poles.