How is the back EMF of an electric motor calculated?

The motor runs with a wire that passes through the current. It should be known that an energized wire cutting a magnetic inductance wire creates an electromotive force. Therefore, at this time, the motor is running to cut the magnetic inductance line, and it will also generate electromotive force.

Judging by the right-hand rule, the direction of this electromotive force is opposite to the voltage applied at both ends of the motor, so the electromotive force generated here is called back electromotive force.

So uit=i 2rt+ek ek refers to kinetic energy.

If no back EMF is generated.

There should be uit=i 2rt, which means that all the electrical energy is converted into heat.

However, uit=i 2rt+ek, which means that part of the electrical energy is converted into heat energy and part of it into kinetic energy (mechanical energy).

The self-induced electromotive force produced by the main magnetic flux in the stator windings is called the back EMF.

Expressed as e1, its valid value is calculated as follows:

e1=where: ke--- is the proportionality constant;

fn --- is the frequency of the stator current;

nl--- is the number of turns of the stator winding per phase;

- The amplitude value of the main magnetic flux.

e-inverse=u-ir(Also, since there is no internal resistance, e=u).

The voltage added to the motor is subtracted from the voltage that generates heat, which is called u-i r

For electric motors, back EMF is the means of generating mechanical work, the process of converting electrical energy into mechanical energy.

Cutting generates a dynamic electromotive force.

Let the electromotive force of the power supply be E, regardless of the internal resistance. The voltage at the end of the road is U, the current is I, and the internal resistance of the motor is R. Find the back EMF of the motor.

The back electromotive force of an electric motor refers to the electromotive force induced in a motor due to the action of a magnetic field when the rotor rotates. The magnitude of the back electromotive force is directly proportional to the speed of the motor, and the speed of the motor can be calculated by the reverse positive electromotive force. Specifically, this can be done by following these steps:

Measuring the back EMF of the motor: By connecting the windings of the motor, the back EMF of the motor is measured with an electric meter (generally with a volt meter).

Calculate the speed of the motor: According to the back electromotive force of the motor and the electromagnetic parameters of the motor (such as the number of poles, current, voltage, etc.), the speed of the motor can be calculated using the following formula:

n = 60f / p

Wherein, n represents the speed of the motor (in the unit of revolutions and minutes), f represents the frequency of the motor back electromotive force (in hertz), and p represents the number of poles of the motor.

For example, assuming that the back EMF frequency of a 4-pole motor is 60 Hz, the motor speed can be calculated according to the above formula:

n = 60 x 60 4 = 900 rpm

It should be noted that this method is only applicable to AC motors, and for DC motors, the corresponding calculation method needs to be carried out according to different types of motors. At the same time, the calculated motor speed is only an approximation, and the actual speed is also affected by other factors, such as load and mechanical losses.

There is a certain relationship between the back EMF of the motor and the speed of the motor. Back electromotive force refers to the self-induced electromotive force generated by the rotor movement during the operation of the motor, and its magnitude is closely related to the speed of the motor.

Generally speaking, the back EMF of an electric motor is directly proportional to the speed of rotation. When the rotational speed of the electric motor increases, the back EMF also increases. This is because an increase in the rotational velocity of the rotor results in an increase in the rate of change in the magnetic flux, which induces a greater self-induced electromotive force.

The increase of the anti-electric grip will reduce the voltage difference in the windings of the motor and limit the flow of current, so the speed of the motor is controlled to a certain extent.

Conversely, when the load of the motor increases or the supply voltage decreases, the speed of the motor decreases, and the back electromotive force also decreases. This causes the voltage difference in the motor windings to increase, prompting more current to flow through the motor, providing greater output torque to overcome the load.

It is important to note that the specific relationship between the back EMF of an electric motor and the rotational speed depends on the design and characteristics of the motor. The relationship between back EMF and rotational speed may be different for different types of motors (such as DC motors, asynchronous motors, permanent magnet synchronous motors, etc.) and under different operating conditions.

Therefore, when designing and controlling electric motors, specific motor characteristics need to be analyzed and considered to achieve the required speed regulation and performance requirements.

The self-induced electromotive force generated by the main magnetic flux in the stator windings is called the back electromotive force, which is denoted by e1, and its effective value is calculated as follows:

e1=where: ke--- is the proportionality constant;

fn --- is the frequency of the stator's electro-trapped posture and auspicious current;

nl--- is the number of turns of the stator winding per phase;

- The amplitude value of the main magnetic flux.

Back electromotive force refers to the tendency to resist the change of electric current and generate electromotive force, which is essentially induced electromotive force. Back EMF generally appears in solenoid coils, such as relay coils, solenoid valves, contactor coils, motors, inductors, etc.

Under normal circumstances, as long as there is an electrical equipment with inductive load that is converted by electric energy and magnetic energy, at the moment of power on, there will be back electromotive force, but at the moment of power off, the back electromotive force is proportional to the size of the disconnection current, when the current is very large, the change amount of current is very large, the time is very short, the rate of change of magnetic flux is very large, and the back electromotive force will also be very high. Back EMF has many hazards, is not well controlled, and can damage electrical components.

The deciding factors are:

1. Rotor angular velocity.

2. The magnetic field generated by the rotor magnet.

3. The number of turns of the fixed bozi winding.

4. Air gap. When the motor is designed, both the rotor magnetic field and the number of turns of the stator windings are determined, so the only factor that determines the back EMF is the rotor angular velocity, or rotor speed, and as the rotor speed increases, the back EMF also increases. The air gap (the difference between the inner diameter of the stator and the outer diameter of the magnet) affects the magnitude of the magnetic flux of the windings and thus the back EMF.

The calculation is as follows:

e1=where: ke--- is the proportionality constant; fn --- is the frequency of the stator current; nl--- is the number of turns of the stator winding per phase; - The amplitude value of the main magnetic flux.

The electromotive force generated by the main magnetic flux in the stator winding is called the back EMF starvation.

When the motor is running, there is a wire that passes through the current, and it should be known that the energized wire will produce electromotive force when cutting the magnetic inductance line, so at this time, the motor will also generate electromotive force when cutting the magnetic inductance line. Judging by the right-hand rule, the direction of this electromotive force is opposite to the voltage applied at both ends of the motor, so the electromotive force generated here is called back electromotive force.

You need to figure out where the current is going first.

As a DC generator, driven by the prime mover, the armature rotation produces a blind induced electromotive force, and the current is output outward under the action of the electromotive force, and the armature current ia is in the same direction as the electromotive force ea, as shown in the figure, the armature electromotive force is also called the power electromotive force. For DC motors. The induced electromotive force is also generated in the conductor of the armature conductor, but because it is in the opposite direction to the voltage applied externally, the electromotive force EA is in the opposite direction of the armature current ia, as shown in the figure, the armature electromotive force is a back electromotive force.

This is the <> of parallel excited DC motors

The armature current is opposite to the direction of the armature electromotive force, and the armature electromotive force is also called the back electromotive force

As a DC generator, the current direction is viewed by the junction current method, ia=i+if