Comrades who understand motors, can you tell me the difference between single capacitor and double c

Single capacitor motors are generally used for low-power motors, and the only function of this single capacitor is to help the motor start, such as: washing machine, refrigerator, air conditioning motor. Single-phase dual-value capacitor asynchronous motor, also known as "capacitor starting and running", refers to a motor with starting capacitance and running capacitance.

The starting capacitor is mainly to increase the starting torque of the motor, and when the motor reaches about 75% of the rated speed, it is disconnected from the starting winding of the motor by the disconnection device. This starting device is generally called a single-phase dual-value capacitor asynchronous motor, which has high power, such as: power tools for decoration, large equipment.

A single capacitor is a capacitor, and a double capacitor is two single capacitors made in a shell. Single and double are used as needed, and there is no difference in quality.

When the speed reaches 75% of the rated speed, a capacitor is disconnected by the internal centrifugal switch (larger capacitor), and then there is only one capacitor left to work with the coil to produce phase shifting. Of course, the starting torque of the motor with dual capacitors is larger. When the load is heavy, it is difficult to start a motor with a single capacitor.

Because the starting torque of a single-phase motor is weaker, the greater the motor power, the weaker the starting torque. Therefore, low-power (300W) motors are single-capacitor; High-power (500W) motors are usually equipped with an extra capacitor to increase the starting torque to assist start, and the capacitor will automatically detach from operation when it is successfully started (rated speed 75%).

There is no relevant formula for the distribution capacitance of single-phase motors, and can only be calculated and derived by formulas.

1. The optional formula of single-phase double-value motor running capacitor: C 1100 i u cos, where 1100 is a coefficient of the empirical formula, i is the rated current of the motor, and u is the power supply voltage; COS is the power factor of the motor (between, generally appropriate).

2. The formula for calculating the current of a single-phase motor is: P=IUCOS. P is the power of the single-phase motor, I is the motor current, generally for the request, U is the motor voltage, generally 220V, COS is the power factor of the motor, generally taken, if there is specific data according to the actual situation.

For example, a single-phase motor with a power of is calculated, and the operating current is calculated; p=l uxcos, 丨=p u cos =1500 165=, capacitance value: c 1100 i u cos 1100 .

Precautions for the use of single-phase motors.

Machinery that uses single-phase motors should be fitted with low-voltage electric shock safety devices and always keep them sensitive and reliable.

Machinery that has not been used for a long time or is damp should be put into trial operation before being put into normal operation. If it does not run after powering on, it must be immediately turned off for maintenance.

Machinery operators should strengthen their awareness of safety precautions and strictly implement operating procedures. When operating, wear insulated shoes, do not wipe electrical equipment with hands and damp cloths, do not hang clothes on wires, etc.

According to the operating capacitance per 100 watts, it is selected according to the micromethod. Because the motor within 1kw selects 200 micro-method 450v, and the motor within 2000w can be selected according to 300-400 micro-method.

The formula for calculating the operating capacitance of a single-phase motor: GC=1950i UCOS (microfar) where: i:

Motor current, U: single-phase supply voltage (220V), COS: power factor, take, 1950:

constant, after calculating the operating capacitance of a single-phase motor, the starting capacitance is several times the working capacitance.

How it works. When the single-phase sinusoidal current passes through the stator winding, the motor will produce an alternating magnetic field, the strength and direction of this magnetic field change with time as a sinusoidal law, but it is fixed in the spatial orientation, so it is also called the alternating pulsating magnetic field. This alternating fluctuating magnetic field can be decomposed into two rotating magnetic fields that are opposite to each other at the same speed and in the direction of rotation, and when the rotor is stationary, these two rotating magnetic fields produce two torques of equal magnitude and opposite directions in the rotor, so that the resultant torque is zero, so the motor cannot rotate.

Operating capacitance capacity c = 120000 * i, where: i is the current; f is the frequency; u is the voltage; cos is the power factor.

The operating capacitor operating voltage is greater than or equal to (2).

Starting capacitance capacity = (Operating capacitance capacity.

The starting capacitor operating voltage is greater than or equal to U.

Split-phase capacitor capacity formula: c=350000*i 2p*f*u*cos withstand voltage formula: u (capacitance) greater than or equal to c is the capacitance; i is the current; f is the frequency; u is the voltage; The power factor is 2p=2 high, and the power factor is 2p=4;cos is the power factor.

Operating capacitance capacity formula of double-value capacitor: c=120000*i 2p*f*u*cos 2p= withstand voltage formula: u (capacitance) is greater than or equal to (2 starting capacitance capacity formula:

c = (running) withstand voltage formula: u (capacitance) is greater than or equal to the capacitor is too large, resulting in excessive motor current and large starting torque. Hope it helps you Follow-up:

550W current: approximately. Running c= Startup c= (Running Follow-up: Thank you!

Like you calculated, you take 4, and the power factor is low to take 4, and then take this how to explain it?

1. The operation mode is different.

The secondary winding of a single-capacitor starting asynchronous motor is connected in series with a larger capacity starting capacitor (C) and centrifugal switch (K) in series with the main winding and connected to the power supply. When the speed of the motor reaches 75 80 of the synchronous speed, the centrifugal switch cuts off the auxiliary winding and starts the capacitor power supply.

After the secondary winding of the double-capacitor running asynchronous motor is connected in series with a running capacitor whose capacity is much smaller than that of the single-capacitor starting asynchronous motor, it is connected to the power supply in parallel with the main winding, and the secondary winding and the running capacitor are always involved in the operation of the motor.

2. The starting torque is different.

Single-capacitor started asynchronous motor has a higher starting torque, which is generally about 2 8 times of the rated torque. The starting torque of the single-capacitor running asynchronous motor is low, generally about 0 5 times of the rated torque. Dual-capacitor asynchronous motors have high starting torque and overload capacity.

Generally, it is about 2 to 5 times of the rated torque.

3. The power factor is different.

The power factor of a single capacitor started asynchronous motor is low, generally in the range of 0 6 0 82. The power factor of single-capacitor running asynchronous motor is higher, generally 0 8 0 95. The power factor of the dual-capacitor asynchronous motor is higher, generally in 0 82 0 9.

4. Different uses.

Single-capacitor start asynchronous motors are commonly used in small air compressors, refrigerators, water pumps, oil pumps, and small mechanical equipment that can start at full load. Dual-capacitor running asynchronous motors are commonly used in ventilators, electric fans, ventilation fans, washing machines, water pumps, oil pumps, and various small mechanical equipment with no-load and light-load starting.

The starting torque of the single-phase motor is poor, the greater the motor power, the worse the starting torque, therefore, the motor power is equal to or less than 550W should be used to start and run with a single capacitor; Greater than or equal to 750W usually uses dual capacitors, one of which is the smaller value is the operating capacitance and the larger value is the auxiliary starting capacitance, which is disconnected after successful start-up.

1. The capacitance is different: double capacitance refers to a motor with starting capacitance and running capacitance, and single capacitance refers to only starting capacitance.

Second, the role is different: the starting capacitor is mainly to improve the starting torque of the motor, when the motor reaches about 75% of the rated speed, it is disconnected from the starting winding of the motor by the detachment device; The running capacitor also helps to start at the beginning of the motor, but it has been running with the motor, and its main role is to balance the electromagnetic relationship between the main winding and the auxiliary winding of the motor to maximize the power of the motor and reduce noise and vibration.

3. Different use scenarios: single capacitors are generally used in relatively large single-phase motors with a power of more than 300W; Dual capacitors are generally used in motors below 300W.

The main differences between single-value and double-value of single-phase motor are:

The single value is used on the capacitor-started motor, which generally has a large capacity. The double-value is used in the motor that has both starting and running, the capacitance is large and small, the large is used for starting, and the small is used during operation, which is smaller.

The single-value capacitor is the starting capacitor and the running capacitor, and the double-value capacitor is the starting capacitor and the other is the running capacitor.

Summary. One of the double capacitors is the starting capacitor, which has a strong start-up and is generally equipped with a double capacitor for single-phase motors with large power.

Is it better to have 1 capacitor or double capacitor for a single-phase motor?

One of the double capacitors is the starting capacitor, which has a strong start-up and is generally equipped with a double capacitor for single-phase motors with large power.

The formula for calculating the working capacitance of a single-phase motor: GC=1950i UCOS (microfar) where:

i: motor current, u: single-phase supply voltage, cos: power factor, take, 1950: constant.

Note: If the single-phase electricity is taken as 220vrms, then:

GC=1950I UCOS =1950P (U2)COS=1950*P (220*220)*, where P is the motor power. After calculating the working capacitance of the single-phase motor, the starting capacitance is 1-4 times of the working capacitance (the larger the starting capacitance, the greater the starting current (the greater the interference to the external power grid), the increase of the starting torque, and the faster the starting.

Conversely, if the starting capacitance is smaller, the starting current will be smaller (and the interference to the external power grid will be smaller), the starting torque will be smaller, and the starting will be slower. The withstand voltage must be greater than the maximum peak value of the AC input voltage (220VRMS*, 400V withstand voltage or higher can be used.

Withstand voltage formula: U (capacitance) greater than or equal to.

Single-phase operating capacitance formula: C 1950 i u cos (with one capacitor, it is both a starting capacitor and a running capacitor, commonly used in small capacity motors such as electric fans and washing machines).

Starting capacitor capacity formula: c=3500*i u*cos (with a capacitor is only put in at start, disconnected during normal operation, and switched with a transfer switch or centrifugal switch.)

The capacitor selection of the motor has strict voltage requirements, which must be equal to or greater than more than the rated voltage of the motor. For a power supply with a rated voltage of 220V, the rated voltage of the capacitor shall not be lower than 400V. The capacitance value has a certain generality, and it doesn't matter if it is large or small, especially the starting capacitance, which can be selected at 2-6 times of the working capacitance.

Define that a single-phase asynchronous motor is composed of a stator, a rotor, a bearing, a casing, an end cover, etc. Single-phase asynchronous motor is often made into small motor equipment, its motor capacity is very small, only need to be powered by single-phase AC power supply, as a driving motor, single-phase asynchronous motor power only needs a few watts, tens of watts or hundreds of watts.

How it works. A single-phase asynchronous motor is a rotating electric machine powered by a single-phase AC power supply, and its stator windings are single-phase. When the single-phase alternating current is connected, it will produce an alternating pulsating magnetic field in the stator and rotor air gap, so the single-phase asynchronous motor cannot start itself. [2] In AC motors, when the stator windings pass through an alternating current, an armature magnetodynamic potential is established, which has a great influence on both the motor energy conversion and the running performance.

Therefore, the single-phase AC winding is passed into the single-phase AC to generate a pulsating magnetodynamic potential, which can be decomposed into the sum of two rotating magnetodynamic potentials with equal amplitude and opposite speeds, so as to establish the sum of forward and reverse magnetic fields in the air gap. These two rotating magnetic fields cut the rotor conductor and generate an induced electromotive force and an induced current, respectively, in the rotor conductor.

This current interacts with the magnetic field to produce positive and negative electromagnetic torques. The forward electromagnetic torque attempts to make the rotor rotate forward; The reverse electromagnetic torque attempts to reverse the rotor. The superposition of these two torques is the resulting torque that pushes the motor to turn.

1. Generally, the operating capacitance is selected according to the micromethod per 100 watts. The start-up capacitor is open after start-up, so it can be selected over a wide range. The motor within 1kw can be selected as 200 micro-method 450V, and the motor within 2000W can be selected according to 300-400 micro-method.

2. Single-phase motor generally refers to a low-power single-phase asynchronous motor powered by a single-phase AC power supply (AC220V). This type of motor usually has a two-phase winding on the stator, and the rotor is a normal squirrel cage type. The distribution of the two-phase windings on the stator and the power supply can produce different starting and running characteristics.

The third is written in reverse, double capacitors for high-power single-phase motors.

The main difference is in power, and single-phase dual-value capacitor motors are generally above.

The former is a relatively large (750W) motor, and the latter is a relatively small (750W) motor. Because the starting torque of the single-phase motor is weak, it is difficult to start the motor with relatively large power, so it is necessary to connect a capacitor with a larger capacity to assist the start, and disconnect the capacitor after successful start (75% of the rated speed).