Why is the starting winding of a single phase motor connected in series with a capacitor, and the vo

1. The running winding of the single-phase motor can only produce a pulsating magnetic field - the electromagnetic field corresponding to any point of the motor stator can only be made at that point, including the change in polarity direction and amplitude. In other words, a rotating magnetic field cannot be formed.

Three-phase power supplies, on the other hand, can generate a rotating magnetic field. ]

2. The capacitor winding, in space, is orthogonal to the running winding, that is, it is 90 degrees [electric angle, for motors with 4 poles and more than 4 poles]. If the capacitor winding is connected with the same power supply as the running winding, then the magnetic field generated by the synthesis of the two windings is still a pulsating magnetic field.

3. In fact, a capacitor with a certain capacity is connected in series in the capacitor winding, so that the equivalent circuit of the winding becomes a circuit in series between the resistance inductance and the capacitor, as long as the capacitance value meets the phase angle of the current at a certain angle ahead of the voltage, such as 30 degrees;

4. At the same time: if the current lag voltage of the inductive running winding is 60 degrees, then the current phase difference between the two windings reaches 90 degrees [close to it]. In this case, the maximum point of the electromagnetic field in the circumference of the stator occurs periodically at intervals of 90 degrees of electric angle – thus creating a rotating magnetic field.

At this point, it is only natural that the motor will spin.

5, and without the capacitor, 3 cannot be realized. So there will be no result of 4. Therefore: capacitors are required.

The starting winding of the single-phase motor is connected with a capacitor in series, so that the current of the starting winding runs ahead of the current of the starting winding by 90°; Note that the current of the starting winding is ahead of the current of the starting winding, so the oscilloscope shows 2 waveforms with different phases, or whether the current lags behind the voltage or the voltage is ahead of the current.

The DC resistance of the starting winding of the single-phase motor is large. The starting winding and running winding of the single-phase motor that can be reversed are interchangeable, with the same diameter, number of turns, and DC resistance. The starting winding coil of a single-phase motor rotating in one direction has a small diameter, a small cross-sectional area, a large number of turns, a long wire and a large resistance.

The running winding coil has a large diameter, a large cross-sectional area, a small number of turns, and a short stool wire, so the resistance is small. Because the DC resistance of the coil and the cross-sectional area of the wire are inversely proportional to the length of the wire.

The working principle of a single-phase motor:

There are two forms of single-phase capacitor starting electric clear Zheng motor, the motor started by single capacitor is larger in size, the main winding wire diameter is thicker, and the starting coil and starting capacitor are used for phase shifting start when starting, and the starting winding and starting capacitance are automatically cut off by the internal centrifugal switch of the motor after starting, and the main winding is operated separately.

The double-value capacitor motor is small in size, the main winding wire diameter is thinner, not enough for the nominal wattage, after the motor starts, only the centrifugal switch cuts off the starting capacitor with a larger capacity, and the starting coil continues to run by the capacitor access circuit with a smaller capacity in series, which is equivalent to adding a small power motor to participate in the operation, and its power accounts for about 30% of the total power.

Compared with the two, the former due to the use of a winding, the volume is larger and the heat dissipation performance is better, the motor pumping will not be hot for a day, the motor involved in the operation of the starting coil, due to the small size, relies on the starting coil operation to compensate for the lack of power, its heat dissipation, and the unevenness of the magnetic field, the performance is not as good as the single capacitor motor, but the production investment is lower.

The starting winding of the single-phase motor is connected with a capacitor in series, so that the current of the starting winding runs ahead of the current of the starting winding by 90°; Note that the current of the starting winding is ahead of the current of the starting winding, so the oscilloscope shows 2 waveforms with different phases, or whether the current lags behind the voltage or the voltage is ahead of the current.

Single-phase motors have two windings, namely the starting winding and the running winding.

The two windings differ by 90 degrees spatially. A capacitor is connected in series on the starting winding, and when the running winding and the starting winding pass through a single-phase alternating current, the current in the starting winding is 90 degrees ahead of the current of the running winding in time due to the action of the capacitor, and reaches the maximum value first. Two identical pulsed magnetic fields are formed in time and space, a rotating magnetic field is produced in the air gap between stator and rotor, under the action of rotating magnetic field, induced current is generated in motor rotor, and current interacts with rotating magnetic field to produce electromagnetic field torque, makes motor rotate.

Hello, first of all, the capacitance phase shift, the capacitor is energized, the circuit will charge the capacitor, the current of the instantaneous charging at the beginning is the maximum, the voltage tends to 0, as the capacitor charge increases, the current gradually decreases, the voltage gradually increases, to the end of the capacitor charging, the capacitor charging current tends to be 0, the capacitor terminal voltage is the maximum value of the circuit, so that a charging cycle is completed, if the terminal voltage of the capacitor is taken as the output, you can get a phase shift voltage that lags behind the current 90 degrees; In order for a single-phase motor to rotate, it must have a rotating magnetic field. Single-phase motor has two windings, the two windings are 90 degrees apart in space, and the voltage lag current is 90 degrees to generate a rotating magnetic field.

Others ask why the current can be advanced after string capacitors. After starting the winding string capacitor, as the voltage of the capacitor rises, the capacitive reactance increases, and the magnetic flux change rate of the starting winding decreases rapidly, and the inductive reactance decreases faster than that of the running winding. When the inductive reactance is equal to the capacitive reactance, the current is maximum.

The operating winding has no capacitive voltage to cancel, and its larger inductive reactance lasts longer. The inductive reactance is proportional to the rate of change of magnetic flux, and the change in magnetic flux is proportional to the rate of change of current. Note that the rate of change of current is not the magnitude of the current, but the ratio of the amount of change of the current to time.

It's like acceleration and speed differences.

The one with the largest resistance value is the start-up winding resistance. I'll tell you a little bit more about the principle:

There are two forms of single-phase capacitor starting motor, the motor started by single capacitor is larger in size, the main winding wire diameter is thicker, the starting coil and starting capacitor are used for phase shifting start-up when starting, and the starting winding and starting capacitor are automatically cut off by the internal centrifugal switch of the motor after starting, and the main winding is operated separately. The double-value capacitor motor is small in size, the main winding wire diameter is thinner, not enough for the nominal wattage, after the motor starts, only the centrifugal switch cuts off the starting capacitor with a larger capacity, and the starting coil continues to run by the capacitor access circuit with a smaller capacity in series, which is equivalent to adding a small power motor to participate in the operation, and its power accounts for about 30% of the total power. Compared with the two, the former due to the use of a winding, the volume is larger and the heat dissipation performance is better, the motor pumping will not be hot for a day, the motor involved in the operation of the starting coil, due to the small size, relies on the starting coil operation to compensate for the lack of power, its heat dissipation, and the unevenness of the magnetic field, the performance is not as good as the single capacitor motor, but the production investment is lower.

Generally, the DC resistance of the secondary winding is large. Some of the two sets of resistors are the same (such as ordinary automatic washing machine motors).

Any single-phase motor has a large secondary winding unless the motor is short-circuited between turns.

One starting coil, one running coil, and the running coil is large.

This is used to help the motor start.

Single-phase motor starting method:

The starting methods of AC single-phase motors are roughly divided into the following types:

The first type, the split-phase starting type, is assisted by the auxiliary starting winding, and its starting torque is not large. The operating rate remains roughly constant. Mainly used in electric fans, air conditioning fans, motors, washing machines and other motors.

Second, when the motor is stationary, the centrifugal switch is turned on, and the starting capacitor participates in the starting work after the power is given, and when the rotor speed reaches 70% to 80% of the rated value, the centrifugal switch will automatically jump off, and the starting capacitor completes the task and is disconnected. The starting winding is not involved in the running work, while the electric motor continues to act by running the winding coil.

Third, when the motor is stationary, the centrifugal switch is turned on, and the starting capacitor participates in the starting work after the power is given, and when the rotor speed reaches 70% to 80% of the rated value, the centrifugal switch will automatically jump open, and the starting capacitor completes the task and is disconnected. The running capacitor is connected in series to the starting winding to participate in the operation. This connection method is generally used in places with large and unstable loads, such as air compressors, cutting machines, woodworking machine tools, etc.

For motors with centrifugal switches, if the motor does not start successfully in a short time, the winding coil will quickly burn out.

A single-phase alternating current is a current that varies with time in a sinusoidal pattern. The magnetic field generated by it is not a rotating magnetic field but a pulsating magnetic field. Therefore, a single-phase current cannot generate a starting torque.

However, under the action of external force, the single-phase motor pushes the rotor of the motor clockwise or counterclockwise to bypass an angle, then the rotor of the motor will produce a torque that pushes the rotor to rotate under the action of the pulsating magnetic field, so that the rotor rotates. Therefore, the single-phase motor itself cannot produce starting torque, and must add auxiliary starting equipment or starting winding before it can start by itself.

This capacitance is called the starting capacitor, and the capacitor is used to divide the phase, the purpose is to make the current in the two groups produce a phase difference of nearly 90, so as to generate a rotating magnetic field to rotate the motor; In a three-phase motor, the current between each two phases has a phase difference, so there is no need to split the phase, and there is no need for capacitors to start.

Generally, the capacitor is connected in series on the negative coil, and the phase angle of the winding energized with the capacitor should be a little sluggish, so that a torque can be formed on the rotor to promote the motor to rotate.

For the split phase. Gets a starting torque. It doesn't have to be a capacitor. Capacitors are cheap though. and nodes.

Single-phase motor starting capacitance:

1.The start-up of single-phase motor, this capacitor is also called single-phase motor start-up capacitor, from the perspective of circuit principle, it plays the role of phase shifting, because single-phase motor only has a set of running windings, and the rotor is squirrel cage type.

2.The rotor winding of the single-phase motor starting capacitor squirrel cage asynchronous motor is named because its shape resembles a squirrel cage, and its structure is embedded in the trunking of the copper strip as a conductor, and the two ends of the copper strip are welded together with short-circuit rings. Squirrel cage rotors can be used on single-phase or three-phase motors.

3.Single-phase electricity can not produce a rotating magnetic field, need another set of starting windings to cooperate, because there is only a single-phase 220 volt alternating current, so a capacitor is connected in series on the starting winding, the characteristic of the capacitor is that the voltage can not change abruptly, so that the current of the starting coil is 90 ° ahead of the running coil, so that the rotating magnetic field is generated in the stator space, and the rotor will cut the magnetic field lines and produce an induced current to form an induced magnetic field, and the two magnetic fields of the stator and rotor interact with each other. The magnetic field induced by the rotor will interact with the magnetic field of the stator, causing the rotor to rotate with the magnetic field of the stator, and the direction of the rotor of the single-phase single machine is consistent with the direction of the rotating magnetic field, so that the rotor can rotate continuously, so that the motor can start normally.

4.Single-phase motors have a capacitor called a starter capacitor. There are two capacitors, one is the starting capacitor and the other is the running capacitor, and generally the capacity of the starting capacitor is greater than the capacity of the operating capacitor.

5.When the single-phase start-up motor capacitor dries up, it is necessary to replace it with a new capacitor of the same capacitance.

Shanghai Zuoli Motor Co., Ltd.