The Simple Electric Motor

A simple electric motor is composed of six parts, the armature or rotor, the switch, the brushes, the shaft, the field magnet and the DC power supply.

The coil of the electric motor rotates between two permanent magnets, where the magnetic coil poles, represented by magnets are attracted by the opposing poles of the fixed magnets. The coil rotates and takes these magnetic poles as close as possible baldor motors to each other, but when it reaches that position the current direction is reversed and then the poles that are facing begin to repel, continuing to propel the rotor. The two ends of each wire, which is a wire for each pole are welded in one terminal and each of the three terminals is connected to one of the switch boards.

The use of the commutator is to periodically change the current direction in the armature periodically twice each time to ensure that the torque always has the same clockwise direction and prevents the armature from being stopped in a balanced position. The reason it is necessary to switch the armature current is that the magnetic flux that is caused by a permanent magnet for simplicity.

Universal Engine Features

The universal electric motors have a high starting torque, develop high speed, are built for voltages of 110V and 220V direct current or alternating current and generally their power does not exceed 300W, except in special cases. This type of motor is applied to most portable appliances and some portable machines used in the industry. The universal electric motor is a motor that allows connection in both the DC and the AC, because its rotor as well  114166.00 mrosupply as its stator are formed by ferrosilicon plates, which minimize the heat effects caused by the currents induced in the metallic masses, when under the action of a variable magnetic field.

In the grooves of the stator are housed the field coils which are generally two, necessary for the formation of the inductor field. In the grooves of the rotor the induced coils are directly wound, whose end points are properly connected to the blades forming the collector. The armature and the inductor field are connected in series. To reverse the direction of rotation, simply reverse the connections on the brush holders, or the connections of the inductor field coils, when gluing connections to the manifold, are equivalent to both directions.

Basic or Primary Specifications

There are three important factors to consider when selecting a DC motor for an application: speed, torque, and voltage. The speed of the axis of a DC motor applies a voltage to rotate an axis at a proportional speed of rotation. Shaft speed is offered in revolutions or revolutions per minute (RPM). Specifications generally refer to the unloaded speed, which is the maximum speed the motor can reach when no torque is applied.

The output torque is when the axis rotation generates a rotational force called torque and that torque is given in units of force-distance. It can be of two types: starting torque or continuous torque. https://www.mrosupply.com/motors/ac-motors/general-purpose-motors/221425_09600100_leeson/ The torque of a DC motor is proportional to the induction current, in which case we have the torque constant. The importance of the torque constant is certain. At the available voltage, DC motors can be designed to operate at a specific voltage if needed. We should not forget that because the speed depends on the voltage, the power supply may be a limitation if an adequate specification of the DC motor is not made.

Characteristics of the operation of synchronous motors

Synchronous electric motors have two possible excitation factors which are the direct current in the field winding and that of the three-phase alternating current source in the armature. If your field current is exactly enough to produce the required magnetomotive force, requiring no magnetizing current or reactive power, the electric motor runs at unit power factor. If your field current is less than what is said to be necessary when the motor is underexposed, insufficiency in magnetomotive force needs to be restored by the armature, the motor runs at a delayed power factor. gates at mrosuppy

If your field current exceeds what is said, when the motor is over-excited, the surplus magnetomotive force must be properly balanced in the armature and an advanced current component is present, the motor will run at an advanced power factor. The synchronous motor when operating in the overexcited and empty condition is called the synchronous capacitor and performs the same function as a capacitor bank, being more economical than static capacitors.

Rated Speed

Rated speed is the speed (rpm) of the electric motor running at nominal power, under rated voltage and frequency. The mechanical speed will depend on the slip, the number of poles and the frequency of the mains. The speed of the induction motor changes very little between the vacuum and full load condition, typically around 5% and in motors with high slip up to 10%. In this way, the induction motor fed from the utility grid is not very correct where variable speed is required.

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Since the motor speed depends on the frequency and number of poles, there will be a limited number of speeds for the induction motors fed directly from the network. However, when fed by means of a static converter, the speed variation is permissible over a very wide range. There are engines that can be operated at two or more speeds from the reconnection of their windings, such as the engine known as Dahlander. This type of motor generally offers a degree of utilization of the active material, lower than standard motors.

Auto-trafo Compensator

An option for the activation of three-phase induction motors with load is the starting with auto-trafo compensator, commonly called compensator. The start is in two stages, and in the first, the power supply to the motor happens with reduced voltage through the autotransformer. At the start of the starting, the current peak and the conjugate are decreased proportionally to the square of the transformation ratio and according to the tap of the transformer, this transformation ratio can be 65 or 80%. The motor torque bearings still reaches the first stage, which is faster than that achieved in the star-delta system. In the second stage, after the initial start time, the neutral point of the autotransformer is opened, the motor is turned on under full voltage, returning to its nominal characteristics.

The motor voltage is reduced proportionally with the transformer taps, and when using the 65% position, the line current is almost equal to that of the star-delta starting system. However, in the transition from the reduced voltage to the full voltage, the motor will not be switched off, so the second peak current is greatly reduced, because the auto-trap for a short period of time becomes a reactance connected in series with the motor.

Motor start with split winding

For application of split winding, it is necessary for the electric motor to have two circuits in parallel per phase. Two steps are used to connect the motor to the mains, where a contactor connects part of the winding to the mains (usually half the winding) for a short time, approximately 4 seconds and another contactor connects the remainder of the winding to the mains, completing the call. This method can be used when the engine starts at a vacuum, and only after reaching the nominal speed does the other part of the winding connect, and then the load is applied and the load gradually increases with the rotation. Example: Fans, centrifugal pumps, etc … mrosupply bearings

The curves represent the conjugate x velocity of the split winding start method. The starting conjugate developed by the split winding method is admirably smaller than the direct starting conjugate, and is even smaller than the full charge conjugate. This should be an advantage when you want a soft match. In this method, the motor will accelerate the load until it is close to the rated speed, ie the load resistant torque must always be lower than the torque developed with the split winding.

Single and three phase motors

Small power induction motors are single phase, and they often require special starting devices because they do not have their own starting. The induction motors of higher power are three-phase and have their own start and need special devices for this current at the time of their departure. Single-phase electric motors have both lower power output and power factor. They are most commonly used for loads requiring small power engines such as motors for fans, refrigerators, portable drills, washing machines, clocks, and compressors, among others. Depending on their operation, single-phase motors can be qualified in two types: Universal Motor and Induction Motor find baldor em4114t here.

Three-phase motors as the name already explains need to be connected to three-phase electrical systems and are also the most widely employed engines in the industry. Its speed is indicated by the frequency of the power supply, which guarantees excellent conditions for its operation at constant speeds. It is also known as an asynchronous motor because it does not operate at synchronous speed, and has as a major disadvantage the fact that in its direct starting the current value is very high, almost ten times its rated current.

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