Interpretation of the meaning of each data on the nameplate of a three-phase asynchronous motor

The motor is a device that converts electrical energy into mechanical energy. To use the motor correctly, you must first be able to understand its nameplate. The meaning of each data on the nameplate of a three-phase asynchronous motor is as follows:

1. Model

The motor model usually consists of product code, specification code and special environment code.

1. Product code

The product code of an electric motor usually consists of a type code, a feature code, and a design serial number.

1) Type code

The type code indicates the type of motor and is expressed in Chinese phonetic letters.

The code name of asynchronous motor is Y, and the full name of Y series motor is fully enclosed self-fan cooled three-phase squirrel cage asynchronous motor.

2) Characteristic code

The characteristic code indicates the performance and structure of the motor and is represented by letters.

(1) Performance

YB is a flameproof explosion-proof motor; YBX3 is the latest designed high-efficiency energy-saving flameproof motor; YBF is a dust explosion-proof motor; YBP is a flameproof variable frequency motor; YBS is a special explosion-proof motor for conveyors.

(2) Structure

B3 is a structural type with a base with feet and no flange on the end cover; B5 is a structural type with no feet and a flange larger than the base on the end cover; B35 is a structural type with feet and a flange larger than the base on the end cover.

3) Design serial number

Indicates the order of product design, expressed in Arabic numerals. The design serial number is not marked for the first design of the product, and the products derived from the series are marked according to the design sequence.

For example: Y3, YB3, YBX3.

2. Specification code

The motor specification code is mainly expressed by center height, base length, core length and number of poles.

1) Center height

The center height refers to the height from the motor axis to the base foot surface. According to the center height, the motor can be divided into four types: large, medium, small and micro.

2) Length of machine base

The length of the machine base is indicated by internationally accepted English letters: S for short machine base, M for medium machine base, and L for long machine base.

3) Core length

Use Arabic numerals 1, 2, 3, 4, etc. to represent them from long to short.

4) Number of poles

It is divided into 2-pole, 4-pole, 6-pole, 8-pole, 10-pole, 12-pole and so on.

3. Special environment code

The special environment code indicates the special working environment in which the motor can be used, and is represented by specific letters or letters plus numbers.

G is used for high altitude; H is used for ships ("sea"); W is used for outdoor; F is used for chemical anti-corrosion; T is used for tropical areas; TH is used for wet tropical areas; TA is used for dry tropical areas.

2. Rated power

The rated power of a motor refers to the mechanical power output on the shaft when the motor is running at rated working conditions. It is generally expressed in kW (kilowatts), but some are expressed in HP (horsepower). The conversion relationship between them is:

1kW=1.36HP, 1HP=0.736kW.

3. Frequency

Frequency refers to the frequency of the AC power supply to which the motor is connected. my country uses a frequency of 50Hz, while the power supply frequency in the United Kingdom, the United States and other countries is 60Hz.

4. Rated speed

The rated speed of the motor is the speed of the motor at rated voltage, rated frequency and rated power. Generally, the rated speed of a 2-pole motor is about 2930r/min, the rated speed of a 4-pole motor is about 1450r/min, the rated speed of a 6-pole motor is about 970r/min, and the rated speed of an 8-pole motor is about 730r/min.

5. Rated voltage

The rated voltage of a motor refers to the line voltage that should be applied to the stator winding of the motor under rated operating conditions. It is the voltage standard level of the power supply used by the motor. According to national regulations, the rated voltage levels of motors include 220V, 380V, 3kV, 6kV, etc.

6. Rated current

The rated current of a motor refers to the line current of the stator winding of the motor at rated voltage, rated power, and rated load. When the stator winding of the motor is connected in a triangle, the line current is √3 times the phase current; when it is connected in a star, the line current is equal to the phase current.

Generally, the motor current is greatly affected by factors such as applied voltage and load, so the rated current of the motor provides a basis for selecting wires, switches, fuses and thermal relays.

7. Insulation grade

The insulation grade of a motor refers to the heat resistance grade of the insulation material used in the motor winding, that is, the maximum allowable temperature. The insulation grade of a motor is closely related to the insulation material used. The better the insulation material, the higher the insulation grade.

Insulation materials can be divided into 7 grades according to heat resistance: Y, A, E, B, F, H, C, and their allowable operating temperatures are: 90℃, 105℃, 120℃, 130℃, 155℃, 180℃ and above 180℃. Y series motors use Class B insulation, which is mainly made of mica, asbestos, and glass fibers bonded or impregnated with organic glue, and its limit temperature is 130℃.

8. Working System

The rated duty of a motor refers to the length of time it is allowed to run continuously under rated conditions. It can be roughly divided into three categories: continuous duty, short-time duty, and intermittent cycle duty.

1. Continuous working system

The continuous duty code is S1, which means that the motor can run continuously for a long time under the rated conditions specified on the nameplate. It is suitable for equipment with constant loads such as water pumps and blowers.

2. Short-time work system

The short-time working system code S2 means that the motor can run for a short time within a limited time under the rated conditions specified on the nameplate. The standard short-time duration quotas are 10 minutes, 30 minutes, 60 minutes and 90 minutes. It is suitable for driving converters, tilting devices and valves, etc.

3. Intermittent cycle working system

The intermittent duty system code S3 means that the motor can only run intermittently and periodically under the rated conditions specified on the nameplate. One working cycle is the constant load running time of the motor plus the downtime and intermittent time, which is specified as 10 minutes. The load duration (the ratio of the rated load duration to one working cycle time, expressed as a percentage) has four standards of 15%, 25%, 40% and 60%. It is suitable for load equipment such as elevators and cranes.

IX. Protection level

The protection level of the motor is divided into the protection level against contact and the protection level against water. The general protection level is IP44, where IP is the abbreviation of the characteristic letters "International Protection", the first "4" means level 4 solid protection (preventing solids larger than 1mm from entering the motor), and the second "4" means level 4 water protection (water splashing in any direction should have no harmful effects).

10. Installation method

There are two types of motor installation: vertical (B) and horizontal (V).

11. Wiring method

Wiring method refers to the connection mode of the motor stator winding. For the Y series medium and small low-voltage asynchronous motors produced in my country, the rated power is above 3KW, the rated voltage is 380V, and the winding is △-connected, that is, U1 and W2, V1 and U2, W1 and V2 are connected with a short-circuit in the junction box, and then the lead wires from U1, V1, and W1 are connected to the three-phase AC power supply respectively; for the rated power of 3KW and below, the rated voltage is 380V, and the winding is Y-connected, that is, U2, V2, and W2 are connected with a short-circuit in the junction box, and then the lead wires from U1, V1, and W1 are connected to the three-phase AC power supply respectively.

12. Power factor cosφ

The power factor cosφ refers to the cosine function of the angle between the current and voltage of the motor at rated power, which is equal to the ratio of active power to apparent power. The closer the power factor is to 1, the smaller its reactive power is, and the smaller the loss in the circuit is. The power factor of the motor is low when it is lightly loaded, about 0.2, and high when it is fully loaded, generally between 0.75 and 0.93.

13. Efficiency (η%)

The ratio of the motor converting electrical energy into mechanical energy is called efficiency. The efficiency reflects the size of the loss, and η% is generally above 85%. The efficiency marked on the motor nameplate refers to the efficiency under rated conditions. The efficiency of the motor will decrease when it is lightly loaded.

14. Other Information

Other information includes bearing model, grease brand, motor weight, manufacturer, production date, etc.