How to choose a contactor compared with a thermal relay, how to calculate the distribution current?

Hello:— 1. The selection of the contactor is determined according to the rated current of the motor, which should generally be more than several times the rated current. Motor'sThe rated current is around 11A, should be used(nominal) 20A contactor

2. The choice of thermal relay is greater than that of the motorCurrent ratingNot, however, of thermal relaysThe setting value (i.e., the rated action value)., should be set in the motorTimes of the rated current value

3. Select the thermal relay to use9 13 or 12 18It can also be usedGeneral purpose (wide) type thermal relays, such as Chint'sNR3 thermal relay, it has a rated current value:

Double the rated current of the motor, but adjust the thermal relay to the rated value after installation.

The rated current of the motor is about 3A, and the magnification is . The range is set with a JR-36 thermal relay. CJX2-0911 is sufficient for contactor. Copper wire for conductors.

Three-phase motor refers to an alternating current motor driven by three-phase alternating current. Three-phase motor It refers to when the three-phase stator windings of the motor (each with a difference of 120 degrees of electric angle), after the three-phase alternating current is introduced, a rotating magnetic field will be generated, and the rotating magnetic field will cut the rotor windings to generate electricity. It includes a three-phase synchronous motor and a three-phase asynchronous motor.

The three-phase asynchronous motor has the advantages of simple structure, low cost, sturdy and durable, easy to manufacture, use and maintenance, and it also has high efficiency and load characteristics close to constant speed, so it can meet the drag requirements of most industrial and agricultural production machinery. Therefore, it is the largest and most widely used motor among all kinds of motors.

According to statistics, more than 80% of the total use of motors in the country is three-phase asynchronous motors, which shows its importance and influence. The disadvantage of the three-phase asynchronous motor is that the power factor is low and the speed regulation performance is poor, but due to the rapid development of AC electronic speed regulation technology, its speed regulation performance has also made great progress, which will further expand its application range.

1.Calculate the line current value: ix=p ( *cos )=1500 (, the motor power factor cos is generally in, and it can be taken smaller when calculating.

2.The circuit breaker is selected according to the above current value, and the 4A specification is selected.

3.The contactor is selected with the specification that is closest to this current value (which must be greater than the calculated value); Optional 9a gear. Such as B9 type.

4.The thermal relay can be selected with the same current specification as the circuit breaker.

Wire 2---5A Thermal Relay 10A Contactor.

3A or so, 10a, square wires.

The configuration of thermal relays, contacts and wires is based on the current rating of the motor.

The rated fighting current of the three-phase motor ie:

ie=1, contactor.

Optional 6A base book contactor.

e.g. NC6-0610 (6A, 1 NO contact).

2. Thermal relay.

Thermal relays from 4-6A are optional.

Such as NXR-25, 4-6A.

3. Cables. Optional cables.

The power factor of 1·5kW three-phase 380V is estimated at 0·8. The current is 2·8A

The contactor is greater than 5A. Over the base of the rental hole thermal protection to take 4-6 ampere, that is, the type of letter can fight dry.

It should be equipped with a thermal relay in the range of 3 to ** to ensure the normal operation of the motor. Optional 10 amp AC contactor. The wire cross-section is selected from 1 to 1 square millimeter.

The kilowatt motor has a customer-specific current of about 10 amps. So use a 20 amp contactor will do. As for the thermal protector, you can choose 10-20 amps.

The motor current is approximately equal to = power kW * multiplied by 2, and can be set at 11A to 14A considering the overload capacity of the motor.

Aluminum core wire below 10 square can carry 5A current per square, copper core wire upgrade calculation, the motor current is estimated to be 20A, 4 square aluminum core wire can be, copper core wire squared can.

The rated current of the motor, AC contactor and thermal relay can be used at 15 to 20A, and the protection current of the thermal relay is adjusted to 15A.

Contactors above 60a, thermal protectors for 12 to 14a.

Since the starting current of the motor is 3 7 times of the normal working current, the contactor cannot be less than 60A

For 18 amp contactors, the maximum thermal relay cannot exceed times the rated current of the motor.

Take CHINT as an example for light load: contactor CJX2-1210 AC220V; Thermal relay JR36-20 Heavy Load: Contactor CJX2-1810 AC220V ; Thermal relay JR36-20 10-16A

What type of contactor and thermal relay to use.

The contactor is large and durable, and it is easy to break if it is selected for long-term use. The thermal relay is directly used on the triangle connection motor is useless, the small one is used for a while to jump, the rated or larger one is selected, the lack of phase motor is not jumped, it needs to be reconnected, the connecting copper sheet of the terminal is removed, and the six wires are introduced to the upper and lower ends of the thermal relay, which corresponds. The rated current of the thermal relay is selected by dividing the rated current of the motor by the rated current.

It achieves the same effect as a star-connected motor.

Summary. Hello pro For motors, it is generally recommended to choose contactors and thermal relays with a rated current of 9-12A. When choosing a contactor and thermal relay for a motor, the following factors need to be considered:

Voltage and current: Select contactors and thermal relays that are appropriate for the current and voltage required for the device. Load Type:

Depending on the type of load, contactors and thermal relays are selected, such as single-phase or three-phase loads. Functional requirements: Contactors and thermal relays can have different functions, such as overload protection, short circuit protection, etc.

Choose the right product for your device's functional needs. Working environment: If there are special conditions in your working environment (e.g., high humidity, high temperature, flammability, etc.), you need to choose a model that is suitable for that environment.

Hello dear to the motor, it is generally recommended to choose a contactor and thermal relay with a rated current of 9-12A. When choosing a contactor and thermal relay for a motor, you need to consider the following factors: voltage and current

Select contactors and thermal relays that are suitable for the current and voltage required by the equipment. Load type: Choose contactors and thermal relays according to the type of load, such as single-phase or three-phase loads.

Functional requirements: Contactors and thermal relays can have different functions, such as overload protection, short circuit protection, etc. Choose the right product for your device's functional needs.

Working environment: If there are special conditions in your working environment (e.g., high humidity, high temperature, flammability, etc.), you need to choose a model that is suitable for that environment.

Three-phase motor is used in high temperature weather.

Running the motor in hot weather needs to pay attention to the following points: choose the appropriate contactor and thermal relay, which can protect the motor from overheating. For three-phase motors, it is recommended to use an AC-3 contactor with a rated current of 16A or above, the rated current of the thermal relay should also match the contactor, and the coefficient of the rated current of the thermal relay should be slightly increased in a high temperature environment to ensure normal operation.

Add a cooling fan to the motor and make sure the motor is well ventilated to remove any blockages. If the motor cannot be cooled properly, it may lead to overheating, damage or even accidents such as fire. In high-temperature environments, motors may require more frequent maintenance and inspections to ensure that all components are working properly.

In particular, the lubrication of motor bearings and the cleaning of cooling systems should be checked and maintained frequently. In conclusion, for three-phase motors, special care is required when using them in hot weather. Proper mechanical maintenance and proper selection of electrical equipment are necessary to ensure the proper operation of the motor.

The current of the AC contactor is selected as (times the working current of the motor, for example, the category of the three-phase motor contactor, the general choice of the motor is AC3 series, the working current of the motor: i=2, and the working current of the AC contactor is selected =.

In general, a two-phase structure thermal relay can be used, but when the three-phase voltage balance is poor, the working environment is harsh or the motor is unattended, the three-phase structure thermal relay should be selected. For electric motors with triangle wiring, thermal relays with phase break protection devices should be selected. The rated current of the thermal relay should be greater than the rated current of the motor.

The type of thermal relay is then selected based on this current rating.

The following estimation method can be used: the rated current of the three-phase asynchronous motor = rated power * 2, that is, 15A, 20A or 25A contactor can be selected; The selection method of the thermal relay: the setting current value is multiple of the rated current. That is, choose about 18a.

1. When the compensation capacity cannot be calculated, the compensation capacity can be calculated according to 10% and 30% of the transformer capacity. 2. Since the capacitor has an inrush current during switching (up to 200 times of the rated current at the maximum), the contactor must use a special contactor for the capacitor, such as CJ19, to limit the inrush current to 20 times. Generally, capacitive contactors are marked with controllable capacitance, such as CJ19-32 can be matched with 18kvar capacitors.

3. According to GB50227, the integer value of the thermal relay is, but at present, many manufacturers in the world do not configure thermal relays, and only use fuses + contactors + capacitors. 4. The thermal relay should be selected according to the motor current for ordinary motors, and generally selected according to the rated current. Another:

The overload protection of high-voltage capacitors is generally set according to the regulations of GBJ3983-83 and IEC standards of "Shunt Capacitors", under the joint action of overvoltage and harmonics, the capacitor should be able to operate under a stable overcurrent with an effective value of times the rated current. If the maximum positive deviation of the capacitor is considered, the overcurrent is allowed to reach the rated current, but the total capacity error of the batch of products in the manufacturing plant cannot reach +10%, so the rated current of the capacitor bank can not be used as the basis for selecting the current-carrying conductor. When there are harmonic sources that exceed the harmonic regulations, a series reactor should be installed to limit the harmonics.

Because the maximum allowable working current of the domestic oil-immersed iron core series reactor is multiple of its rated current, it is considered comprehensively and the time is selected as the basis for selection), for the low-voltage capacitor bank, it can also be selected according to the standard times specified in the "low-voltage reactive power compensation device" (enterprise standard) approved by the Electrical Engineering Bureau of the Ministry of Machinery Industry in 1985.