The slot openings a shut with fibrous wedges to prevent the conductor from plying out due to the high centrifugal force produced during the rotation of the armature, in presence of supply current and field. The commutator of dc motor is a cylindrical structure made up of copper segments stacked together, but insulated from each other by mica. Its main function as far as the dc motor is concerned is to commute or relay the supply current from the mains to the armature winding housed over a rotating structure through the brushes of dc
SUPERIOR PERFORMANCE MODULAR COMBUSTION CHAMBER: The aerospike engine is made up of small thrusters which are easy to develop and less expensive too.This gives greater versatility to the engine. LESS RISK OF FAILURE: It uses simple gas generator with low chamber pressure which reduces the risk of catastrophic explosion. Though the performance may reduce due to low chamber pressure,The high expansion ratio of aerospike makes up for this. LOWER VEHICLE WEIGHT: Though aerospike nozzles tend to be heavier than bell nozzle, it shares major structural elements with vehicle, thereby reducing the weight. LOWER DRAG: The base portion is filled by aerospike nozzle, which reduces the base drag.
Depending on how the stator is wounded, the back-electromagnetic force will have a different shape (the Back EMF is induced in the stator by the motion of the rotor). To obtain the maximum performance from each type of Permanent Magnet Synchronous Motor, an appropriate control strategy has to be implemented. The trapezoidal Back EMF motor called DC brushless motor (BLDC) uses a "two phases on" strategy, whereas the sinusoidal Back EMF motor offers its best performances when driven by sinusoidal currents (three phases on strategy). The rotor of a permanent magnet brushless dc motor (BLDC) is similar to that of a permanent magnet synchronous motor (PMSM). But, its stator is made of concentrated windings.
When the materials are deformed, energy is absorbed and dissipates by the material itself. The effect is due to friction between the internal planes, which slip or slide as the deformations take place. In addition, damping of a system may be describe through the following system 3.4 Over damped A system is said to be a over damped if the system returns to equilibrium positions without oscillating. 3.5 Critically damped A system is said to be a critically damped if the system returns to equilibrium as quickly as possible without
4.1, it is clear that the first decision to be made for the selection of the motor is whether to use a dc brush or a brushless servo. The reasons for choosing brushless servo motor drives over the brush type dc motor drives are well known and include robustness, higher torque speed bandwidths lower maintenance The mechanical commutator and brushes of the dc motor also enforce severe limitations on its maximum speed and overcurrent capabilities. Assuming that it has been decided to use a brushless servo motor drive, the next decision to make is whether to use an ac or a switched reluctance motor. The switched reluctance motor is inherently a pulsating torque machine, although some work has been done in an attempt to reduce the torque ripple. Hence, if a reasonably smooth output torque is required, an induction or permanent magnet machine is to be preferred over the switched reluctance motor.
Accordingly, the turbine is sized to produce high compressor speeds at these low engine speeds. At higher engine speeds where exhaust gas flow is greater, the turbine and compressor can be over-driven, particularly in cruising or part throttle conditions. This over drive reduces engine efficiency by supplying excess airflow in the case of a diesel engine, and by opposing the actions of the throttle in a gasoline engine which is attempting to restrict gas flow to the engine. In both cases excessive exhaust manifold pressure is also created. Conventionally, a waste gate valve may be included to divert exhaust flow from passing through the turbine to reduce compressor speed.
The pipe is in the form of a venturi it narrows in section and then widens again, causing the airflow to increase in speed in the narrowest part. Below the venturi is a butterfly valve called the throttle valve a rotating disc that can be turned end-on to the airflow, so as to hardly restrict the flow at all, or can be rotated so that it (almost) completely blocks the flow of air. This valve controls the flow of air through the carburetor throat and thus the quantity of air/fuel mixture the system will deliver, thereby regulating engine power and speed. The throttle is connected, usually through a cable or a mechanical linkage of rods and joints or rarely by pneumatic link, to the accelerator pedal on a car or the equivalent control on other vehicles or
Protection against Motor timed over current The motor may be able to withstand currents marginally above the rated value, but only if they do not last for long, otherwise continuous operation may lead to thermal damage. To avoid this condition, a protection system monitors the current and trips the circuit if it exceeds the pre-set value. The induction disc relay is usually used for this protection. The relay consists of two coils that produce opposing magnetic fluxes when current flows through them. The fluxes create a torque on the disc and as the current increases, the torque increases to a point where the torque overcomes the spring torque.
A dc servo motor which is usually a dc motor of low power rating is used as an actuator to drive a load. A dc servo motor has a high ratio of starting torque to inertia and hence they make a faster dynamic response. The speed torque characteristic of this motor is flat over a broad range, as the armature reaction is negligible.
The stator is usually low, and receive input signal from a synchro transmitter. Voltage appearing across the terminals of these differences rotor (R1, R2, and R3) are determined by the magnetic field produced by the stator currents, the physical position of the rotor, and the step-up turns ratio between the stator and rotor. Magnetic field created by the stator currents, consider the angle corresponding to a magnetic field in the transmitter supplying the signal. The player controls the amount of magnetic coupling occurs between the magnetic field of the stator and the rotor, and therefore, the amount of induced voltage in the rotor windings. If the player changes in response to mechanical input, the voltage induced in the coil which is also changing.