How many kilowatts does the motor start from with a star delta

If it is only the use of ordinary motors (excluding the use of motors in power plants and industrial production), you can refer to: for civil use, there are two kinds of direct power supply from the public grid and power supply from the transformer in the community, the former allows direct start to be less than 11kw, and the latter is 15kw

In fact, this question needs to be considered according to 4 elements:

1. When the motor starts, the voltage on the distribution bus at all levels meets the normal use requirements of other equipment;

2. The mechanical energy can withstand the impact torque of the motor when it starts at full pressure.

3. The structure of the motor itself can withstand the impact of full-pressure starting.

4. Whether there are special requirements for motor starting.

-The following are some of the contents of the electrical design standards:

Section 3 Starting of the motor.

Article When the motor starts, the terminal voltage should be able to ensure the starting torque required by the machinery, and the voltage fluctuation caused by the power distribution system should not hinder the work of other electrical equipment.

Article When the AC motor starts, the voltage on the distribution bus shall comply with the following provisions:

1. Under normal circumstances, when the motor starts frequently, it should not be lower than 90% of the rated voltage; When the motor does not start frequently, it should not be lower than 85% of the rated voltage.

2. When the distribution bus is not connected to lighting or other loads that are sensitive to voltage fluctuations, and the motor does not start frequently, it should not be less than 80% of the rated voltage.

3. When other electrical equipment is not connected to the distribution bus, it can be determined according to the conditions of ensuring the starting torque of the motor; For low-voltage motors, it should also be ensured that the voltage of the contactor coil is not lower than the release voltage. Article The selection of the starting mode of cage motor and synchronous motor shall comply with the following provisions:

1. When the following conditions are met, the motor should be started at full voltage:

1. When the motor starts, the voltage of the distribution bus conforms to the provisions of Article 1 of this specification

2. The mechanical energy can withstand the impact torque of the motor when it starts at full pressure.

3. The manufacturer has no special regulations on the starting mode of the motor.

2. When the conditions for full-voltage starting are not met, the motor should be started at reduced voltage, or other appropriate starting methods should be selected. 3. When there is a requirement for speed regulation, the starting mode of the motor should be matched with the speed regulation mode.

The current power grid can be directly started below 200kw, and the star delta start is often based on the load to determine whether to use. Generally, the fan should be started by Star Delta to prevent the impeller from being deformed and damaged.

It depends on the power supply capacity. Generally, more than 15 kilowatts are used.

Start with Star Triangle from 10kw.

Summary. More than 11kw motors should be started by star delta.

1. When the load has no strict requirements for the starting torque of the motor and the starting current of the motor is limited, the motor meets the wiring conditions of 380V δ, and the stator is connected into a triangle when the motor is in normal operation, the star-delta starting method can be used;

2. The method is: connect the motor into a star wiring when the motor starts, and then reconnect the motor into a triangle wiring when the motor starts successfully;

3. Because the starting current of the motor is proportional to the power supply voltage, and the starting current provided by the power grid at this time is only 1 3 of the full voltage starting current, so its starting torque is only 1 3 of the full voltage starting torque.

How much power does a motor need to use Star-Delta Star-Delta?

More than 11kw motors should be started by star delta. 1. When the load has no strict requirements for the starting torque of the motor and the starting current of the motor is limited, the motor meets the wiring conditions of 380V δ, and the stator is connected into a triangle when the motor is in normal operation, the star-delta starting method can be used; 2. The method is: connect the motor into a star wiring when the motor starts, and then reconnect the motor into a triangle wiring when the motor starts successfully; 3. Because the starting current of the motor is proportional to the power supply voltage, and the starting current provided by the power grid at this time is only 1 3 of the full voltage starting current, so its starting torque is only 1 3 of the full voltage starting torque.

Have a great day.

More than 15kw, the transformer capacity has no margin, all need to be started by star angle, self-coupling, or soft start. The state stipulates that 7kw will be lowered to start. In order to reduce the impact on the power grid at start-up.

This problem is considered from two aspects, one is the power management department, which has an impact on the power grid when the relatively large equipment starts; Second, for the user's own considerations, if the voltage drop is large when starting, it may cause other equipment within the scope of the unit to not work normally.

As for how big the motor should be considered for step-down starting, in addition to referring to some regulations, the main thing is to look at the electricity conditions.

The state stipulates that 7kW will be started with a step-down in order to reduce the impact on the power grid when starting. This problem is considered from two aspects, one is the power management department, which has an impact on the power grid when the relatively large equipment starts; Second, for the user's own considerations, if the voltage drop is large when starting, it may cause other equipment within the scope of the unit to not work normally.

As for how big the motor should be considered for step-down starting, in addition to referring to some regulations, the main thing is to look at the electricity conditions. The situation is very different between the two units I have worked for. One is a 55kw centrifugal pump, which has always been started directly, sometimes the 55kw centrifugal pump is broken, and it is replaced by a 95kw pump, or it is directly started, and it has been no problem.

Although it doesn't seem to work logically, it's been 20 years since I came into contact with it, and it's fine. The other unit is not good, the 30kw submersible pump must be started under pressure.

Therefore, specific issues need to be considered in detail.

In order to prevent the uneven distribution of the magnetic field of the ions, the vibration and noise of the motor are aggravated by the unbalanced three-phase current, and the motor cannot be started.

When the load has no strict requirements for the starting torque of the motor and the starting current of the motor is limited, the motor meets the wiring conditions of 380V δ, and the stator winding is connected into a triangle when the motor is in normal operation.

The winding is connected incorrectly and causes an incomplete rotating magnetic field, resulting in symptoms such as difficulty in starting, three-phase current imbalance, and high noise, and in serious cases, the winding will be burned out if it is not dealt with in time. There are mainly the following situations: one or several coils in a certain polar phase are inverted or the head and tail are connected incorrectly; The pole (phase) group is reversed; A phase winding is reversed; The multi-way parallel winding branch is connected incorrectly; The "y" connection is incorrect.

More than 11kw motors should be started by star delta.

Principle. 1.When the load has no strict requirements for the starting torque of the motor and the starting current of the motor is limited, the motor meets the wiring conditions of 380V δ, and the stator is connected into a triangle during the normal operation of the motor, the star-delta starting method can be adopted;

2.The method is: when the motor starts, the motor is connected to the star wiring, and when the motor is successfully started, the motor is reconnected to the triangle wiring (quickly switched through the double throw switch);

3.Because the starting current of the motor is proportional to the power supply voltage, and the starting current provided by the power grid at this time is only 1 3 of the full voltage starting current, so its starting torque is only 1 3 of the full voltage starting torque

4.Star-delta starting is a step-down start, which is achieved at the expense of power in exchange for reducing the starting current, so it cannot be generalized to the size of the motor power to determine whether to use the star-delta starting friend, but also to see what kind of load. Generally, in the case of light load at start-up, heavy load when shouting mountain, Zheng Oak Star Triangle can be used, usually the starting current of the squirrel cage motor is 5-7 times of the running current, and the power grid voltage requirements are generally plus or minus 10%, in order to make the motor starting current not form an excessive impact on the grid voltage, you can use the star triangle start.

Generally, it is required that when the power of the squirrel cage motor exceeds 10% of the rated power of the transformer, the star delta should be used;