Why does the stator current increase when the motor is stalled?

When the rotor is stalled in the three-phase asynchronous motor, the stator winding current will rise sharply.

The three-phase asynchronous motor uses the stator to generate a rotating magnetic field, and the rotor cuts the rotating magnetic field to generate an induced current to rotate. When the rotor speed of the motor decreases, the differential speed of the rotor cutting magnetic field lines increases, and the induced current in the rotor increases, the back electromotive force generated in the stator winding decreases, and the stator current increases. When the rotor is stalled, the speed at which the rotor cuts the magnetic field lines reaches the maximum, and the induced current generated is also large, and the current of the corresponding stator winding also reaches the maximum.

1. The rotor coil of the induction motor (including three-phase and single-phase) induction motor is a squirrel cage with a cast aluminum structure, which is in a closed state. During normal operation, the synchronous magnetic field generated by the stator coil cuts the squirrel cage coil and causes the squirrel cage coil to produce induced current, and the magnetic field generated by the induced current interacts with the synchronous magnetic field of the stator and rotates.

2. When the induction motor is stalled (and at the moment of starting), the speed of the synchronous magnetic field cutting the squirrel cage coil is the largest, and the induced current generated is also the largest, because the rotor magnetic field is opposite to the stator magnetic field, so it will cause the current of the stator winding to become larger.

3. The stator winding of the induction motor can be regarded as the primary winding of the transformer, and the rotor squirrel cage is the secondary winding, so the induction motor is also called it.

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When the secondary current increases, the primary current will also increase.

The speed of the stator rotating magnetic field remains unchanged when the AC asynchronous motor is rotating, and the rotor speed is 0.

The rotation magnetic field and the relative slip rate of the rotor become larger, which is equivalent to the rotor coil cutting the magnetic field line faster.

When the rotor coil cuts the magnetic field line at a faster speed, the induced potential increases, and the induced current increases.

The increase of the rotor coil current causes the demagnetization effect to increase, the stator magnetic field is weakened, the induced potential of the stator coil loop decreases, and the external current increases due to the decrease of the induced potential of the stator coil under the condition that the applied voltage remains unchanged.

When the rotor is not moving! The slip rate is 1

The rotor didn't move.

However, the stator coil is supplied with alternating current! The magnetic field produced is periodically changing! At this time, the rotor is equivalent to a magnetic field that constantly cuts a magnetic pole.

A considerable electric current is generated!

According to the turns theorem of transformers! The current in the stator coil can also become very large! If this is the case for a long time.

It will burn out the coil of the motor!

Your question relates to the dynamic characteristics and electrical principles of electric motors. Although the decrease in rotational speed causes the magnetic field generated by the rotor current to cut the stator winding at a reduced speed, thus reducing the back EMF in the stator, at the same time the induced current in the rotor increases, and the strength of the resulting magnetic field does also increase. This is because the increase in the induced current in the rotor leads to an increase in the rotor magnetic field, which increases the strength of the magnetic field.

Also, in the formula you mentioned e=blv, b represents the strength of the magnetic field, l represents the length of the conductor, and v represents the relative velocity of the conductor with the magnetic field. In an electric motor, the relative velocity of the conductor to the magnetic field decreases due to the decrease in the rotational speed of the rotor, so that the magnetic field strength b also decreases according to this formula. However, since the increase in the induced current in the rotor leads to an increase in the resulting magnetic field, the change in the strength of the magnetic field depends not only on the change in relative velocity, but also on the effect of the induced current.

As for the problem of the increase in stator current, according to the equivalent circuit model of the motor, the current of the motor is related to factors such as electromotive force, resistance, inductance, etc. When the load increases, the rotor speed decreases, and the stator back electromotive force decreases, which will lead to an increase in the difference between the electromotive force and the load potential, so that the motor current will increase to maintain the operation of the motor. Therefore, the increase in stator current can be seen as a necessary response to keep the motor running.

Move the bold part of the second paragraph of the original question to the front of the bold part of the first paragraph, and the problem is solved.

At the same time that the rotor speed decreases, the magnetic field generated by the rotor current cuts the stator winding, and the back electromotive force in the stator winding decreasesThe stator current increases

The problem is that although the rotational speed drops,The rotor current magnetic field cuts the stator winding speed decreases,ButAt this point, the induced current in the rotor increasesIsn't the strength of the generated magnetic field also increasing, e = blv, b rising, v decreasing. How to understand the increase in stator current?

The reason why the current increases when the motor is stalled is:

When the motor rotates, the rotating magnetic field formed by the stator winding drags the rotor to rotate, and the magnetic field generated by the induced current in the rotor also induces a back electromotive force in the stator winding, which is the main part of the voltage consumption.

The back EMF is zero when the motor is stalled, the motor only has its own resistance and inductance, and all voltages are loaded on the windings. The natural current will increase considerably. According to the size of the motor capacity and different processing technology, the motor stall current is generally 50-12 times of the rated current of the motor.

1. The stalled rotor current and the starting current are equal in value, but the duration of the starting current and the stalled rotor current of the motor are different, and the maximum starting current appears within the power supply after the motor is connected to the power supply, and decays according to the exponential law over time, and the decay speed is related to the time constant of the motor; The locked-rotor current of the motor does not decay over time, but remains the same.

2. The meaning of the starting current is basically the same as the meaning of the locked-rotor current, the actual starting current is dynamic, there are significant changes in a relatively short period of time, the size of the peak value is related to many factors such as time and the phase of the instantaneous voltage of the power supply, there is a certain randomness, and the starting time of some motors is very short, and it is difficult to accurately represent it with an effective value.

The literal meaning of the locked-rotor current is very clear, but the actual measurement of the large motor cannot be carried out under the rated voltage, so a variety of different experimental methods are derived from the measurement and conversion, there is a step-down, such as 100V, or other values, such as the rated current, and so on.

3. The stalled rotor current is the current generated by fixing the rotor of the motor to send a voltage of 100V, and the starting current is the current generated by the motor at the moment when it just starts together.

4. The stalled rotor current is about two times of the rated current, but the starting current is 3-8 times of the rated current. Therefore, the locked-rotor current is not the same as the start-up current. The starting current is much larger than the locked-rotor current, and the locked-rotor current is essentially constant, while the starting current varies depending on the load.

1. Use external force to fix the motor rotor shaft and the motor shell together, and then energize the motor, at this time the motor does not rotate at all, and the current of the motor is vividly called "stalled current", or the brake is applied to the shaft end to make it stop after the motor rotates, and the stalled rotor current can also be measured.

2. This measurement is used to check the low-speed starting performance and starting torque of the motor, and the torque of the AC and DC series motor is large.

3. The measurement time should be very short, and the motor and power supply or power supply line will be overheated or even burned out after a long time.

Summary. Dear, hello, you want to know whether the stator current and input power change when the rotor of the motor reaches stability before and after the series resistance, why, right? During the operation of the motor, if the rotor reaches a steady state before and after the series of resistance, the stator current and input power will change.

When the rotor is connected with a resistor, the speed of the motor will drop a little due to the appearance of the rotor resistance. According to the theory of the motor, it can be known that when the speed decreases, the reverse electromotive force induced by the electromagnetic induction will also decrease accordingly. Since the input current of the motor is proportional to the stator voltage and the reverse electromotive force of electromagnetic induction, when the speed of the motor decreases, in order to ensure that the stator current remains unchanged, the input voltage and power of the motor need to be increased to offset the effect of the change of motor parameters.

When the motor rotor reaches stability before and after the series resistance, whether the stator current and input power change, and why.

Dear, hello, you want to know whether the stator current and input power change when the motor rotor is connected to the resistance before and after the series resistance is stable, why, right? During the operation of the motor, if the rotor reaches a steady state before and after the series of resistors, the stator current and input power will change. When the rotor is connected with a resistor, the speed of the motor will drop a little due to the appearance of the rotor resistance.

According to the theory of the motor, it can be known that when the speed decreases, the reverse electromotive force induced by the electromagnetic induction will also decrease accordingly. Since the input current of the motor is proportional to the stator voltage and the reverse electromotive force of electromagnetic induction, when the speed of the motor decreases, in order to ensure that the stator current remains unchanged, the input voltage and power of the motor need to be increased to offset the effect of the change of motor parameters.

At the same time, due to the appearance of rotor resistance, the torque of the motor will also decrease accordingly. After the motor reaches steady state, the difference between the torque demand of the motor and the output torque of the motor will cause the stator current to change. Therefore, after the rotor is connected with a resistor, the current and input power of the motor will change.

To sum up, after the rotor is connected with a resistor, the stator current and input power of the motor will change due to the change of motor parameters. We hope that the information on the chain can be helpful to you. <>

<> but the correct answer is the same.

Dear, I'm very sorry, but when the rotor series resistor reaches stability before and after, the stator current and input power will not change, because the parameters of the motor are unchanged in steady-state operation. Under steady-state conditions, the power input of the motor is equal to the output, that is, p = p p p in = p out, and the output power of the motor is determined by the load, so in the steady state, the input power is also constant. At the same time, in the steady state, the speed of the motor is also unchanged, so the amplitude of the electromagnetic induced reverse electromotive force and the input voltage also remains the same, so that the stator current of the motor is also unchanged.

Therefore, when the rotor series resistor is stable before and after the resistance, the stator current and input power of the motor are constant. <>

The cause of the failure of the stator current of the synchronous motor increases, and the rotor current is zero.

1. Motor controller failure: The motor controller may have a control loop failure, resulting in an increase in the stator current and the rotor current being unable to pass. 2. Circuit fault:

It may be that the circuit is short-circuited, leakage and other phenomena, so that the stator current increases and the rotor current cannot pass. 3. Fault of servo control digger: The failure of the servo controller increases the stator current and the rotor current cannot pass.

4. Stator winding damage: the stator winding of the motor is damaged, the resistance is too large, the stator current increases and the rotor current cannot pass. 5. Generator winding damage:

The winding of the motor generator is damaged, and the stator current is too large, resulting in the increase of the stator current and the rotor current cannot pass. 6. Rotor winding loss and return to annihilation: the rotor winding of the motor is damaged, the resistance is too large, the stator current increases and the rotor current cannot pass.

7. Rotor damage: The rotor of the motor is damaged, and the rotor resistance is too large, resulting in the increase of stator current and the inability of rotor current to pass. 8. Power failure:

It may be that the supply voltage is unstable, which causes the stator current to increase and the rotor current cannot pass through.