Torque control of AC motor, what is the torque of a motor?

The motor shaft end output torque is equal to the mechanical power output of the rotor divided by the mechanical angular velocity of the rotor.

The torque of the motor is the product of the radius of the outgoing shaft and the force experienced on the radius. Whereas, the output power of the motor is torque and speed.

The electromagnetic torque should be the theoretical torque of the motor, ignoring the output torque of the friction factor. The output torque of the motor is the electromagnetic torque of the motor minus the friction output torque of the motor. The load torque is the torque that the motor acts on the load through the reducer, etc.

1. When the motor is in the acceleration state, the electromagnetic torque is greater than the load torque, and the direction is opposite, and the former must be greater than the latter, so the motor accelerates.

2. When the motor is in a constant speed state, the electromagnetic torque is equal to the load torque, and the direction is opposite, and the two are equal, so the motor maintains a constant speed.

3. When the motor is in the state of deceleration and braking, the electromagnetic torque and the load torque are in the same direction and brake together.

Load torque: the torque ** moment or torque required when the motor drives to rotate the load);

Electromagnetic torque: When there is armature current flowing through the armature winding, the energized armature winding will be subjected to an electromagnetic force in the magnetic field, and the product of this force and the radius of the armature core of the motor, which is the theoretical output value.

According to the speed formula n = n0 (1 - s ) = 60f1 (1-s ) p, we can intuitively see that the speed regulation of AC motor can adopt pole change speed regulation, frequency conversion speed regulation and change.

There are three basic speed regulation methods, such as slip rate speed regulation.

1. Change the stator pole logarithm p speed regulation.

Under the condition that the power frequency f1 remains unchanged, the motor is changed.

The number of pole pairs, the synchronous speed of the motor n1 will be blocked.

Change. There are two ways to change the number of pole pairs: one is.

Two sets of different poles can be embedded in the stator core groove.

three-phase winding (this method is very uneconomical); The second is profit.

Change the number of pole pairs by changing the connection of the stator winding.

Speed regulation purpose. It should be noted that the motor is set in the change of fierce balance.

At the same time as the number of sub-poles, the number of poles of the rotor must be changed. In order to.

The two-speed motor YY connection method is an example.

1. Necessary conditions: there must be an intersection between the mechanical characteristics of the motor and the torque characteristics of the load, that is, there is T tz.

2. Sufficient conditions: the intersection meets (dt dn-dtz dn) <0.

The electric drive system is composed of a motor and its automatic control device, and the working process of the electric drag system: the automatic control device can realize the automatic control of mechanical equipment through the control of the start and braking of the electric lifting machine, the control of the motor speed adjustment, the control of the motor torque and the control of some physical parameters according to a certain law.

The use of electric tractors can not only liberate people from heavy manual labor, but also liberate people from complex information processing affairs, improve the control performance of mechanical equipment, improve product quality and labor productivity.

The torque of the alternating current lift motor is t=k1i1i2f1f2

where t represents the motor output torque, k1 and k2 represent the proportional constants of the stator and rotor, and f1 and f2 represent the frequencies of the stator and rotor currents, respectively. Respectfully.

The definition of torque is the force multiplied by the force arm, and the popular example is that you use your hand and a wrench to tighten the nut of the bolt, and twist the nut of the same size, using a large wrench will save more effort because the force arm is larger.

Three torques, which belong to the three performance indicators of the motor, are briefly described as follows:

1. The maximum torque refers to the torque when the motor can maintain normal operation, which is the maximum load that can be driven, and in fact, there is a performance index of the minimum torque, that is, the minimum load that can be driven. Beyond these performance indicators, the motor will not be able to operate normally, after exceeding the maximum torque, the motor is in danger of burning, and the front spine blind motor after exceeding the minimum torque belongs to the operating condition of large energy consumption and small output.

2. The rated torque refers to the best operating condition under the rated current (which can be understood as the rated power), which is the best working condition of the motor and the highest efficiency.

3. Stalled torque, also known as short-circuit torque, refers to the torque when the rated voltage is applied to the motor, but the motor is forced to rotate by external force, which directly reflects the starting performance of the motor.

Under normal circumstances, the larger the stalled torque, the better, but too large the stalled torque, the starting current will increase at the same time, resulting in an impact on the power grid. Therefore, in the national standard, the minimum limit of the stalled torque, and at the same time the maximum limit of the starting current.

Motor torque, to put it simply, refers to:The magnitude of the turning force

However, the torque of the motor is proportional to the strength of the rotating magnetic field and the current in the rotor cage, and is proportional to the square of the supply voltage, so the torque is determined by the factors of current and voltage.

Torque motor is a special motor with soft mechanical characteristics and a wide speed range. The shaft of this motor does not output power at constant power, but at constant torque. Torque motors include: DC torque motors, AC torque motors, and brushless DC torque motors.

The principle of automatic torque adjustment of DC motor means that when the load of DC motor changes, the torque can be automatically adjusted by changing the current. When the load of the DC motor changes, if the current is not adjusted, the torque will also change accordingly, resulting in unstable motor operation. In order for the motor to work stably, it is necessary to automatically adjust the current with the change of load, so as to keep the torque constant.

A common method is to use feedback control. That is, an encoder is installed on the output shaft of the motor, which measures the speed of the motor and feeds back the signal to the controller. The controller compares the actual speed with the set speed and adjusts the current according to the difference, so as to realize the automatic adjustment of torque.

In addition, current feedback control is also possible. That is, a current transformer is installed in the motor circuit, the current is measured, and the signal is fed back to the controller. The controller compares the actual current with the set current, and adjusts the power supply voltage of the motor according to the difference, so as to realize the automatic adjustment of torque.

A DC motor is a type of motor that is used to produce rotational motion. Its torque, i.e., torque, can be adjusted by changing the voltage or current of the power supply. The principle of automatic torque adjustment of DC motor is realized through the circuit.

The torque of a DC motor is proportional to the current of the power supply, so the torque of the motor can be changed by adjusting the current. A common method of automatic torque adjustment is the use of feedback control circuits. The circuit detects the speed and torque of the motor in the absence of this, and compares the actual speed volt or speed with the preset speed to adjust the size of the group current.

In this way, the motor can automatically adjust the torque within the preset speed range, so as to ensure the stability and accuracy of the work.