Connecting dimensions of electric motors and diameter of the electric motor shaft (according to GOST)

• Price list of electric motors of the series: AIR, A, 4A, 4AM, 5A, AD, ADM, 5AM.

Comparison of characteristics of externally commutated electric motors

Below are comparative characteristics of externally commutated electric motors from the perspective of application as traction motors in vehicles.

• Comparison of mechanical characteristics of electric motors of different types with limited stator current
• Dependence of power on shaft rotation speed for different types of motors with limited stator current

Note:

Orange color is a low indicator, yellow color is an average indicator, light yellow color is a high indicator.

In accordance with the above indicators, a hybrid synchronous electric motor, namely a synchronous reluctance electric motor with built-in permanent magnets, is most suitable for use as a traction motor in the automotive industry (the choice was made for the BMW i3 & BMW i8 concept cars). The use of reactive torque provides high power in the upper speed range. Moreover, such an engine provides very high efficiency over a wide operating range.

Pump Load and Motor Load Types

The following types of loads are distinguished:

Constant power

The term "constant power" is used for certain types of loads that require less torque as the rotation speed increases, and vice versa. Constant power loads are typically used in metalworking applications such as drilling, rolling, etc.

Constant torque

As the name implies - “constant torque” - it is implied that the amount of torque required to operate a mechanism is constant, regardless of the speed of rotation. An example of such an operating mode is conveyors.

Variable torque and power

“Variable torque” is the category that is of greatest interest to us. This torque is relevant for loads that require low torque at low speed and require higher torque as the speed increases. A typical example is centrifugal pumps.

The rest of this section will focus solely on variable torque and power.

Having determined that variable torque is typical for centrifugal pumps, we must analyze and evaluate some of the characteristics of a centrifugal pump. The use of variable speed drives is subject to special laws of physics. In this case, these are laws of similarity

, which describe the relationship between pressure differences and flow rates.

Firstly, the pump flow is directly proportional to the rotation speed. This means that if the pump runs at 25% higher speed, the flow will increase by 25%.

Secondly, the pump pressure will change in proportion to the square of the change in rotation speed. If the rotation speed increases by 25%, the pressure increases by 56%.

Thirdly, what is especially interesting is that power is proportional to the cube of the change in rotation speed. This means that if the required speed is reduced by 50%, this equates to an 87.5% reduction in power consumption.

In summary, the laws of similarity explain why the use of variable speed drives is more appropriate in applications where variable flow and pressure are required. Grundfos offers a range of electric motors with an integrated frequency converter that regulates the speed to achieve exactly this purpose.

Just like feed, pressure and power, the amount of torque required depends on the rotation speed.

The figure shows a cross-section of a centrifugal pump. The torque requirements for this type of load are almost the opposite of those required for "constant power". For variable torque loads, the torque requirement at low speed is low and the torque requirement at high speed is high. In mathematical terms, torque is proportional to the square of the rotation speed, and power is proportional to the cube of the rotation speed.

This can be illustrated using the torque/speed characteristic we used earlier when talking about motor torque:

As the motor accelerates from zero to rated speed, the torque can vary significantly. The amount of torque required at a given load also varies with speed. In order for an electric motor to be suitable for a particular load, it is necessary that the torque of the electric motor always exceeds the torque required for a given load.

In the example, the centrifugal pump at rated load has a torque of 70 Nm, which corresponds to 22 kW at a rated speed of 3000 rpm. In this case, the pump requires 20% torque at rated load when starting, i.e. approximately 14 Nm. After starting, the torque drops slightly and then increases to full load as the pump picks up speed.

Obviously, we need a pump that will provide the required flow/pressure (Q/H) values. This means that the electric motor must not be allowed to stop, in addition, the electric motor must constantly accelerate until it reaches its rated speed. Therefore, it is necessary that the torque characteristic matches or exceeds the load characteristic over the entire range from 0% to 100% rotation speed. Any “excess” moment, i.e. The difference between the load curve and the motor curve is used as the rotation acceleration.

Power calculator – calculation by current, voltage, resistance

Using the power calculator , you can independently calculate power by current and voltage for single-phase (220 V) and three-phase networks (380 V). The program also calculates power through resistance and voltage, or through current and resistance according to Ohm's law. The cos φ value is taken according to the instructions in the technical data sheet of the device, the average values ​​of the tables below, or calculated independently using formulas. We recommend not changing the coefficient unless necessary and leaving it at 0.95. To get the calculation result, click the “ Calculate ” button.

Related regulatory documents:

• SP 256.1325800.2016 “Electrical installations of residential and public buildings. Rules for design and installation"
• SP 31-110-2003 “Design and installation of electrical installations of residential and public buildings”
• SP 76.13330.2016 “Electrical devices”
• GOST 31565-2012 “Cable products. Fire safety requirements"
• GOST 10434-82 “Electrical contact connections. Classification"
• GOST R 50571.1-93 “Electrical installations of buildings”

Power calculation formulas

Power is a physical quantity equal to the ratio of the amount of work to the time of doing this work. Electric current power (P) is a quantity that characterizes the rate of conversion of electrical energy into other types of energy. The international unit of measurement is Watt (W/W).

— Power by current and voltage (direct current): P = I × U — Power by current and voltage (single-phase alternating current): P = I × U × cos φ — Power by current and voltage (three-phase alternating current): P = I × U × cos φ × √3 — Power by current and resistance: P = I 2 × R — Power by voltage and resistance: P = U 2 / R

• I – current strength, A;
• U – voltage, V;
• R – resistance, Ohm;
• cos φ – power factor.

Calculation of cosine phi (cos φ)

φ is the shift angle between the phase of current and voltage, and if the latter leads the current, the shift is considered positive, if it lags, it is negative.

cos φ is a dimensionless quantity that is equal to the ratio of active power to total power and shows how efficiently energy is used.

Formula for calculating cosine phi: cos φ = S / P

• S – total power, VA (Volt-ampere);
• P – active power, W.

Active power (P) is the real, useful, real power, this load absorbs all the energy and turns it into useful work, such as light from a light bulb. There is no phase shift.

Formula for calculating active power: P (W) = I × U × cos φ

Reactive power (Q) is watt-free (useless) power, which is characterized by the fact that it does not participate in work, but is transmitted back to the source. The presence of a reactive component is considered a detrimental characteristic of a circuit, since the main purpose of the existing power supply is to reduce costs, and not to pump it back and forth. This effect is created by coils and capacitors.

Formula for calculating reactive power: P (VAR) = I × U × sin φ

The total power of an electrical appliance (S) is a total value that includes both active and reactive components of power.

Formula for calculating total power: S (VA) = I × U or S = √( P 2 + Q 2 )

Components of an electric machine

The basis for an electric machine is the rule of electrical induction with magnetic induction. Such a device includes a stator or, as it is called, a constant part (typical for asynchronous, synchronous machines of variable current) or an inductor (for devices of constant current) and a rotor, it is called an active or moving part (for asynchronous and synchronous machines of variable current) or an armature (constant current devices). Magnets (of a constant state) are actively used as a constant part for current machines with low power.

This is interesting: Verification of electricity meters - timing, methodology, cost

How to find out the power of a wheel motor

To make an approximate calculation of the power of the motor-wheel, you need:

1. Measure the current using ammeters connected in series in the circuit. In this case, the ammeter is connected to the open circuit between the battery and the controller.
2. Measure the battery voltage. The voltmeter is connected in parallel to the section of the circuit being tested.
3. Calculate the product of the measured current and voltage values, i.e. power consumption.
4. Multiply the resulting value by the efficiency of the electric motor - we get the amount of power on the MK shaft. The efficiency of the electric motor is indicated by the manufacturer in the documentation and averages 80–90% (when multiplied, the coefficient is 0.8–0.9).

Current and voltage must be measured under load. If you don't have a dynamometer, you should find an alternative. A bicycle computer is suitable for determining speed. Its readings are based on calculations of wheel revolutions and are quite accurate if the correct diameter is specified in the settings.

Then you need to create a load for the electric motor. You can do this in several ways:

1. Measure the acceleration time to the maximum speed on a flat and dry section of asphalt road. Using the previous formula (P=IU), calculate the power developed by the electric motor at maximum acceleration.
2. Use an electric bicycle or other tested vehicle to overcome a section with a uniform rise. Remember the ammeter and voltmeter values. To calculate the power developed during such a rise, the formula P = IU·efficiency is used (0.8 is taken on average). On climbs of varying steepness, it is possible to approximately calculate the power of a particular electric vehicle that it develops under various conditions. The rated power is considered to be the greatest power developed by the electric motor without harming its serviceability.
3. Determine the height of the rise (you can use a GPS navigator) and perform races on it. Calculate the power using the formula P=mgh/t, where m is the total mass of the vehicle and rider in kg, g =9.81, h is the lift height, t is the ride time, P is the power in W.

Online calculation of characteristics of three-phase electric motors

Electric motor power calculation

Electric motor power by current can be calculated using our online calculator:

The result can be rounded to the nearest standard power value.

Standard values ​​of electric motor power : 0.25; 0.37; 0.55; 0.75; 1.1; 1.5; 2.2; 3.0; 4.0; 5.5; 7.5; eleven; 15; 18.5; 22; thirty; 37; 45; 55; 75 kW, etc.

Engine power is calculated using the following formula:

P=√3UIcosφη

• U - Rated voltage (voltage to which the electric motor is connected);
• I - Rated current of the electric motor (taken from the passport data of the electric motor , and in their absence is determined by calculation);
• cosφ - Power factor - the ratio of active power to total power (taken from 0.75 to 0.9 depending on the power of the electric motor);
• η - Efficiency factor - the ratio of the electrical power consumed by the electric motor from the network to the mechanical power on the motor shaft (taken from 0.7 to 0.85 depending on the power of the electric motor);

Motor current calculation

The rated and starting current of an electric motor can be calculated by power using our online calculator:

The rated motor current is calculated using the following formula:

Inom=P/√3Ucosφη

• P - Rated power of the electric motor (taken from the motor’s passport data or determined by calculation);
• U - Rated voltage (voltage to which the electric motor is connected);
• cosφ - Power factor - the ratio of active power to total power (taken from 0.75 to 0.9 depending on the power of the electric motor);
• η - Efficiency factor - the ratio of the electrical power consumed by the electric motor from the network to the mechanical power on the motor shaft (taken from 0.7 to 0.85 depending on the power of the electric motor);

The starting current of the electric motor is calculated using the formula:

Istart=Inom* K

• K - Starting current multiplicity, this value is taken from the electric motor passport, or from catalog data (in the above online calculator, the starting current multiplicity is determined approximately based on the other specified characteristics of the electric motor).

Calculation of electric motor power factor

Online calculation of power factor (cosφ) of an electric motor

Calculation of cosφ (cosine phi) of the engine is carried out using the following formula:

cosφ=P/√3UIη

• P - Rated power of the electric motor (taken from the motor’s passport data or determined by calculation);
• U - Rated voltage (voltage to which the electric motor is connected);
• I - Rated current of the electric motor (taken from the passport data of the electric motor , and in their absence is determined by calculation);
• η - Efficiency factor - the ratio of the electrical power consumed by the electric motor from the network to the mechanical power on the motor shaft (taken from 0.7 to 0.85 depending on the power of the electric motor);

Calculation of electric motor efficiency

Online calculation of efficiency (efficiency) of an electric motor

The efficiency of the electric motor is calculated using the following formula:

η=P/√3UIcosφ

• P - Rated power of the electric motor (taken from the motor’s passport data or determined by calculation);
• U - Rated voltage (voltage to which the electric motor is connected);
• I - Rated current of the electric motor (taken from the passport data of the electric motor , and in their absence is determined by calculation);
• cosφ - Power factor - the ratio of active power to total power (taken from 0.75 to 0.9 depending on the power of the electric motor);

Did you find these online calculators useful? Or maybe you still have questions ? Write to us in the comments!

Didn’t find an article on the website on a topic that interests you regarding electrical engineering? Write to us here. We will definitely answer you.

Electric motor connection diagram

Nominal data are given in accordance with GOST 28173-89.

AIR electric motors designed for a voltage of 220/380V must be connected when the windings are connected in a star to a linear voltage of 380V, and when the windings are connected in a delta to a linear voltage of 220V.

Similarly, AIR electric motors designed for a voltage of 380/660V must be connected when the windings are connected in a “star” to a linear voltage of 660V, and when the windings are connected in a “delta” to a linear voltage of 380V.

For electric motors designed for a voltage of 380V, the windings are by default connected in a “star” for a linear voltage of 380V.

A different connection of the windings will lead to failure of the electric motor and the manufacturer’s refusal of warranty obligations due to the presence of “consumer fault”.

How to calculate three-phase current power

The DC power in an electrical circuit is determined in a simple way by multiplying the current and voltage. These quantities are constant and not subject to changes over time, therefore the power value will be constant, since the entire system is in a balanced state.

Alternating current differs from direct current in all respects, especially in the presence of the number of phases. Very often situations arise when it is necessary to calculate the power of three-phase current in order to correctly determine the characteristics of the connected load. Carrying out such calculations requires special knowledge about the operation of a three-phase power system. Three-phase networks, along with single-phase ones, have become widespread due to low material costs and ease of use.

Characteristics of a three-phase system

Three-phase circuits are usually connected in two main ways - a star (Fig. 1) and a triangle, which will be discussed below. In all diagrams, for more convenient use, the phases are designated by the symbols A, B, C or U, V, W.

When using a star circuit (Fig. 1), the value of the total voltage at the phase intersection point N is equal to zero. In this case, three-phase current, compared to single-phase, will have constant power. This position indicates the balance of the three-phase system, and the instantaneous total power will be expressed as the formula:

A star connection is characterized by two types of voltage - phase (Fig. 2) and linear (Fig. 3). In the first case, the voltage is determined between one of the phases and the exact zero crossing N. Line voltage corresponds to the voltage that exists between the phases themselves.

Therefore, the apparent power value for a star connection is given by the following formula:

However, the difference between line and phase voltages of √3 must be taken into account. Therefore, it is necessary to calculate the sum of the powers of all phases. To calculate active power, the formula P = 3 x Uph x Iph x cosφ is used, and for reactive power - P = √3 x Ul x Iph x cosφ.

Another common method of phase connection is the “triangle”.

This type of connection assumes the same value of phase (Uph) and linear (Ul) voltage.
The relationship between phase and linear currents is determined in the form of the formula I = √3 x Iph, according to which the value of the phase current will be Iph = I x √3.
Thus, the powers of linear quantities with this connection method will be expressed using the following formulas:

• Total power: S = 3 x Sph = √3 x U x I;
• Active power: P = √3 x U x I x cosφ;
• Reactive power: Q = √3 x U x I x sinφ.

At first glance, the power formulas for each type of connection seem to be the same. In the absence of sufficient knowledge and experience, this may lead to incorrect conclusions. To avoid such errors, you should consider an example of a typical calculation.

• The electric motor connection is made in the form of a triangle, the network voltage is 380 V, the current is 10 A. Therefore, the total power value will be as follows: S = 1.73 x 380 x 10 = 6574 V x A.
• Next, the same electric motor was connected by a star. In this case, each phase winding began to receive a voltage 1.73 times lower than when connected by a triangle, although the mains voltage remained the same. Accordingly, the current strength in the windings also decreased by 1.73 times. There is another important point: if, when connected by a triangle, the linear current was 1.73 times higher than the phase current, then later, when the circuit changed to a star, their value became equal. As a result, the decrease in line current was: 1.73 x 1.73 = 3 times.
• Thus, different values ​​are used in the same formula: S = 1.73 x 380 x 10/3 = 2191 V x A, therefore, when the electric motor is reconnected from a delta to a star circuit, the power decreases by 3 times.

Measuring power with a wattmeter

In electrical networks, power is measured using a special device - a wattmeter. Connection diagrams may be different, depending on the load connection and its characteristics. In the case of a symmetrical load (Fig. 1), only one phase is used for measurements, and the results obtained are then multiplied by three. This method is the most economical, allowing you to significantly reduce the size of the measuring device. It is used in cases where there is no need to obtain accurate data for each phase.

In the case of an asymmetrical load (Fig. 2), the measurements will be more accurate. However, to measure the power of each phase, three instruments with large overall dimensions will be required. You will also have to process readings from all three devices.

Calculation of three-phase current power and its measurement can be performed in an electrical circuit in the absence of a neutral conductor (Fig. 3). In this scheme, two instruments are used, and Kirchhoff’s first law is used for calculations: IA+IB+IC=0. Thus, the readings of two wattmeters add up to give the three-phase power value for a given circuit.

How to calculate cable cross-section based on power

Three-phase network power calculation

How to calculate wire cross-section by power

Connecting a three-phase motor to a three-phase network

Vladimirus-team

Motor current I = P /(1.73 *U *efficiency* Cosph);

The rated data of the electric motor are indicated on the nameplate or in other technical documentation.

• 1.73 is the root of three;
• U (Volt) - linear voltage;
• P (Watt) - Power of an asynchronous motor
• Efficiency (η) - efficiency factor, taken from the passport data, or in the range 0.8 -0.9;
• Cos(F) - power factor is taken from the passport data, or in the range 0.8 - 0.9.
• I (Ampere) current;

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Comments

nonsense - the rated current of an electric motor with a power of 55 kW is 1 Ampere.

Hello. You took into account that the power in this calculator must be indicated in Watts.

That is, in the power field we indicate 55000, not 55.

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Mifflin-St. George formula for calculating calories

The Mifflin-St. Geor basal metabolic formula The Mifflin-St.

Calculation of basic metabolism: Mifflin-San Geor formula for a woman: BOO = 10 * weight (kg) + 6.25 * height (cm) – 4.92 * age – 161; Mifflin-San Geor formula for a man: BOO = 10 * weight (kg) + 6.25 * height (cm) – 4.92 * age + 5; By calculating the basal metabolic rate (BMR) using the Mifflin-Saint-Geor formula, you can calculate the approximate number of calories needed per day to maintain body weight, taking into account the level of physical activity.

To do this, multiply the resulting number by the physical activity coefficient.

Physical activity coefficients (K) Minimum load (sedentary work) - K = 1.2 A little daily activity and light exercise 1-3 times a week - K = 1.375 Workouts 4-5 times...

Air conditioner power calculation

The approximate calculation of the cooling power Q (in kilowatts) is made according to the generally accepted method:

Q = Q1 + Q2 + Q3

, where Q1

- heat inflows from windows, walls, floors and ceilings.

Q1 = S * h * q / 1000

, where: S - room area (m2); h—room height (m); q is a coefficient equal to: q = 30 for a shaded room; q = 35 for average illumination; q = 40 for rooms that receive a lot of sunlight. If the room receives direct sunlight, the windows should have light-colored curtains or blinds.

Q2

— the sum of heat inflows from people. Heat gain from an adult: .1 kW

- in a calm state;
0.13 kW
- with light movement;
0.2 kW
- during physical activity;
Q3
is the sum of heat inflows from household appliances.
Heat gain from household appliances: 0.3 kW
- from the computer;
0.2 kW
- from the TV; For other appliances, it can be assumed that they emit 30% of the maximum power consumption as heat (that is, the average power consumption is assumed to be 30% of the maximum...

Heater power calculation

Calculation of heater power Before choosing a heater, you need to calculate the minimum thermal power of your room.

The power depends on: the volume of the room that will need to be heated, the temperature difference between the room and the outside. dissipation coefficient, which directly depends on the insulation of the room and the type of structure. The dispersion coefficient has certain constant values. wooden structures or metal (without thermal insulation) the coefficient is 3-4. with little thermal insulation in a simplified room design 2-2.9. average thermal insulation and standard design coefficient ranging from 1 to 1.9. improved thermal insulation (brick walls, double thermal insulation, thick floor, high-quality roof material), coefficient is 0.6-0.9. To calculate the power of the heater, a simplified system for calculating the required thermal power of the gun, air heater, heater is used: P=V * Δ T * k/860. Heater power calculation onlineRoom height: ...

Table of sizes of electric motor shafts according to GOST power

Electric motors from 56 to 180 dimensions have 4 holes on the flange.
from 200 to 355 dimensions - 8 holes. Electric motors from 56 to 180 dimensions have 4 holes on the flange. from 200 to 355 dimensions - 8 holes.

Determining the power of an electric motor without a tag

If there is no technical certificate or tag on the engine, the question arises: how to find out the power of an electric motor without a plate or technical documentation? The most common and fastest methods, which we will discuss in the article:

• According to shaft diameter and length
• By dimensions and mounting dimensions
• By winding resistance
• By no-load current
• By current in the terminal box
• Using an induction meter (for household electric motors)

Determining engine power by shaft diameter and length

The simplest ways to determine the power and brand of an engine are the overall dimensions - shaft or mounting holes. The table shows the lengths and diameters of the shafts (D1) and length (L1) for each model of an asynchronous industrial three-phase motor. Go to detailed overall dimensions of AIR electric motors

When replacing a broken Soviet electric motor with a new one, it often turns out that there is no nameplate on it. We are often asked questions: how to find out the power of an electric motor? How to determine engine speed? In this article we will look at how to determine the parameters of an electric motor without a tag - by shaft diameter, dimensions, current. Order a new electric motor by phone

Modern designation and decoding of electric motor parameters

The marking has several main positions:

• brand (type) of electric motors;
• execution option;
• working length of the axis of rotation;
• mounting mounting dimensions;
• core length;
• number of pole pairs;
• design modification;
• Climatic performance.

Below is a breakdown of the designations of modern engines.

Below you see an example of complete marking of asynchronous motors and its explanation.

The degree of protection of the electric motor from dust and moisture according to IP class is also indicated, with numbers from 0 to 8. Here the first number is protection from dust, and the second is from moisture.

In this case, the name indicates the installation version. Using the installation code, you can determine how the motors are mounted - on feet or using a flange. For example, IM 1081 talks about foot mounting and that it can be installed with the shaft up, down or horizontally.

For an explosion-proof electric drive, the package of accompanying documents must contain a certificate that indicates the marking according to the degree of explosion protection, its type and scope of application. Also, in the engine marking, if the letter B is indicated at the beginning, it is explosion-proof, for example VA07A(M)-450-710.

In this case, the designation of DC motors differs from alternating current and has the form shown in the figure.

The figure below provides information about traction motors mounted on cranes.

Similar data is placed on the nameplates of electric motors.

The information on the plate says that:

• AIR – type of asynchronous machine;
• 80 – shaft length;
• A-installation size;
• 4-number of poles;
• U - designed for work in moderate climates;
• 3-installed indoors.

Power 1.1 kW, rotation speed 1420 rpm. Can operate on alternating current voltage of 220 or 380 volts when the windings are connected with a delta or star.

The current consumption will accordingly be 4.9/2.8A. Protection degree IP54. Made in the Republic of Belarus.

Possibilities for choosing general industrial electric motors

An important advantage in working with domestically produced equipment is its interchangeability. Given the same technical characteristics and overall dimensions of general industrial electric motors, their manufacture in accordance with general specifications or GOST allows replacement at the discretion of engineers. At the same time, modern manufacturers offer a wide range of equipment, which differs from each other in their design, electrical, and operational characteristics. All this allows you to select a unit that will be focused on work as part of installations associated

• with frequent starts,
• increased slip performance,
• pulsating loads,
• using multiple rotation speeds,
• different climatic conditions.

Overall dimensions of general industrial electric motors

In modern mechanical engineering, there is a direct relationship between the power of general industrial electric motors and their overall dimensions. If the unit is manufactured in accordance with GOST R 51677, then with its power not exceeding 100 kW, its dimensions will vary between 112-250 mm. At the same time, higher power motors, in accordance with the same regulatory document, are characterized by increased efficiency indicators with dimensions of 280-355 mm.

General industrial electric motors AIR (GOST)

Legend:

1 – series (type) 2 – electrical modifications 3 – height of the rotation axis (dimensions) 4 – core length and/or frame length 5 – number of poles 6 – design modifications 7 – climatic version 8 – placement category

9 – degree of protection 10 – power 11 – rotation speed (synchronous) 12 – mounting design

series (type) of electric motor:

Installation of the AIR electric motor

Three-phase asynchronous electric motors for general industrial use of the AIR series are designed to complete electric drives of mechanisms in various sectors of the national economy.

Electric motors can be equipped with a temperature protection sensor for stator windings and bearing units (optional).

In addition, electric motors of the AIR series can be equipped with SKF/NSK bearings (optional).

Overall, installation and connection dimensions of AIR engines

* - overall and installation dimensions of engines can be changed by the manufacturer without additional notice.

Overall, installation and connection dimensions of motors with a small flange (IM2181)

Technical characteristics of AIR electric motors

** - the actual weight of electric motors may differ from that indicated in the table.

How to determine the power of an electric motor

How does an electric motor work?

The operation of the motor is based on the principle of electromagnetic induction. The device consists of two parts. The fixed part is the stator for AC motors or the inductor for DC motors. The moving part is the rotor for AC motors or the armature for DC motors. Manufacturers produce motors of different technical characteristics and configurations, but the moving and fixed parts remain unchanged.

What is electric motor power

The power of an electric motor characterizes the rate of conversion of electrical energy; it is usually measured in watts. To understand how this works, we need two quantities: current and voltage. Current strength is the amount of current that passes through a cross section over a period of time; it is usually measured in amperes. Voltage is a quantity equal to the work done to move a charge between two points in a circuit; it is usually measured in volts.

In simple terms, current and voltage can be compared to water. Current strength is the speed at which water flows through pipes. The voltage can be seen in the example of two containers connected to each other by a tube. If you place one container higher than the other, water will flow out until the levels in both containers are equal. It is the difference in height that will be the tension. After you place the plug between the two containers, the flow of water (current) will stop, but the voltage will remain.

To calculate power, use the formula N = A/t, where:

N—power;

What about work;

t — time.

Electric motor power calculation

Manufacturers indicate all technical parameters of electrical equipment. “Why do any calculations then?” you say. But the fact is that the declared power is not the actual power of the electric motor, but the maximum permissible power of the electric flow. So, if your appliance or tool says 1000 watts, for example, it's not what you think it is.

Three ways to determine the power of an electric motor

There are dozens of ways to calculate power. We will not talk about each of them, focusing only on the simplest and most accessible ones.

First way. Calculation using tables

For this calculation method you will need a ruler or caliper. Using them, measure the diameter of the shaft of your electric motor, the length of the motor (do not take into account the protruding parts of the shaft) and the distance to the axle. Using the obtained figures, you can determine the power of the electric motor from the tables of motor technical characteristics. Finding such tables is not difficult - they are publicly available on the Internet. Having opened the table, determine the series of the electric motor and, accordingly, its technical characteristics.

Second way. Calculation by meter

This method is considered the simplest; you do not need any additional equipment or calculations. Before you start measuring motor power, turn off all electrical appliances from the network. Turn on the electric motor under test and run it for 5-7 minutes. If your home has a modern meter, it will show the load in kilowatts.

Third way. Calculation by dimensions

For this method you will need a ruler or caliper. Measure the diameter of the core from the inside and the length (take into account the length of the ventilation holes). Determine the mains frequency and the synchronous shaft speed. Multiply the core diameter in centimeters by the synchronous shaft speed, multiply the resulting value by 3.14, divide by the network frequency multiplied by 120.

Determination of shaft speed

Three-phase asynchronous motors are divided into 4 types based on rotor speed: 3000, 1500, 1000 and 750 rpm. min. Here is an example of marking based on AIR 180:

1. AIR 180 M2 – where 2 is 3000 rpm.
2. AIR 180 M4 - 4 is 1500 rpm. min.
3. AIR 180 M6 – 6 indicates a rotation speed of 1000 rpm.
4. AIR 180 M8 - 8 means that the output shaft rotation speed is 750 rpm.

The easiest way to determine the number of revolutions of a three-phase asynchronous electric motor is to remove the rear casing and look at the stator winding.

For a 3000 rpm engine, the stator winding coil occupies half a circle - 180 °, that is, the beginning and end of the section are parallel to each other and perpendicular to the center. For electric motors at 1500 rpm the angle is 120°, at 1000 rpm it is 90°. A schematic view of the coils is shown in the drawing. See the table for all motor winding data.

How to determine power?

There are several ways to determine the power of an electric motor: by shaft diameter, by size and length, by current and resistance, by measuring with an electricity meter.

By overall dimensions

What dimensions need to be measured:

• Length, width, height of the case
• Distance from center of shaft to floor
• Shaft length and diameter
• Mounting dimensions for feet (flange)

By shaft diameter

Determining the power of an electric motor by shaft diameter is a common request for search engines. But this parameter is not enough to accurately determine - two engines of the same size, with the same shafts and rotation speed can have different power.

A table relating shaft diameters to power and speed for AIR and 4AM engines.

According to the meter reading

Typically, meter measurements are displayed in kilowatts (hereinafter referred to as kW). For accurate measurements, you should turn off all electrical appliances or use a portable meter. The power of the electric motor is 2.2 kW, which means that it consumes 2.2 kW of electricity per hour.

To measure power using a meter reading you need:

1. Connect the motor and let it run for 6 minutes.
2. Multiply the meter measurements by 10 - we get the exact power of the electric motor.

Calculation of power by current

First you need to connect the motor to the network and measure the voltage readings. We measure the current consumption on each of the phase windings using an ammeter or multimeter. Next, we find the sum of the currents of the three phases and multiply them by the previously measured voltage indicators, clearly in the formula for calculating the power of the electric motor by current.

• P – electric motor power;
• U – voltage;
• Ia – 1st phase current;
• Ib – 2 phases;
• Ic – 3 phases.

If you couldn’t find out the power and rpm

If you are unable to find out the power and speed of the electric motors or you are not sure of the measurements, contact the specialists of Quality Systems. Our specialists will help you choose the right motor or repair a broken AIR motor.

The table provides information on the diameter of the electric motor shaft and its dimensions depending on the power and shaft speed.

The connecting dimensions of electric motors are given according to the GOST 2479-79 standard (“according to GOST”). On the domestic market there are electric motors with connection dimensions according to the DIN standard. In our practice, such electric motors are most often found as part of imported equipment.

The connecting dimensions according to GOST and DIN differ slightly. I wrote about these differences here.

And one more thing: the table shows the connection dimensions for a “standard” flange (IM 2081). Some electric motors can be equipped with a flange of reduced size (IM2181, about which our customers call it “small flange”). To clarify the dimensions of the “small” flange connection, please contact us.

Practical measurements

The most accessible way is to check the readings of your household electricity meter. First, you should turn off absolutely all household appliances and turn off the lights in all rooms, since even a burning 40W light bulb will distort the readings. Make sure that the counter does not spin or the indicator does not blink (depending on its model). You are lucky if you have a Mercury meter - it shows the load value in kW, so you only need to turn on the engine for 5 minutes at full power and check the readings.

Induction meters record in kW/h. Record the readings before turning on the engine, let it run for exactly 10 minutes (it is better to use a stopwatch). Take new meter readings and find out the difference by subtraction. Multiply this figure by 6. The resulting result displays the engine power in kW.

If the engine is low-power, calculating the parameters will be somewhat more difficult. Find out how many revolutions (or pulses) are equal to 1 kW/h - you will find the information on the meter. Let's say it's 1600 rpm (or indicator flashes). If the meter makes 20 revolutions per minute when the engine is running, multiply this figure by 60 (the number of minutes in an hour). This turns out to be 1200 rpm. Divide 1600 by 1200 (1.3) - this is the engine power. The result is more accurate the longer you measure the readings, but a small error is still present.

Definition from tables

How to find out the power of an electric motor by shaft diameter and other indicators? On the Internet it is not difficult to find technical tables with which you can find out the type of motor and, accordingly, its power. You will need to clear the following settings:

• shaft diameter;
• its rotation frequency or number of poles;
• mounting dimensions;
• flange diameter (if the engine is flanged);
• height to the center of the shaft;
• motor length (without protruding part of the shaft);
• distance to the axis.

Next is a matter of time and attentiveness. Agree, it is more reliable to measure the details and find out the exact result, without errors. The network has parameters for absolutely everything, even very old motors.

Calculation by number of revolutions per minute

Visually determine the number of stator windings. Use a tester or milliammeter to find out the number of poles - no need to disassemble the motor. Connect the device to one of the windings and rotate the shaft evenly. The number of needle deflections is the number of poles. Please note that the shaft rotation speed with this calculation method is slightly lower than the result obtained.

Determination by dimensions

Another way is to carry out measurements and calculations. Many of those who are interested in how to find out the power of a three-phase motor prefer it. You will need the following data:

Core diameter in centimeters (D). It is measured from the inside of the stator. The length of the core is also required, taking into account the ventilation holes.

Gross rotation frequency (n) and mains frequency (f).

Using them, calculate the polar division index. D multiplied by n and by Pi - let's call this reading A. 120 multiplied by f - this is B. Divide A by B.

As you can see, to calculate the value, it is enough to remember the school mathematics course.

Determination by the power produced by the engine

Here again you will have to arm yourself with a calculator. Find out:

• number of shaft revolutions per second (A);
• indicator of engine draft force (B);
• shaft radius (C) - this can be done using a caliper.

The electric motor power in W is determined using the following formula: Ax6.28xBxC.

Why do you need to know engine power?

Of all the technical characteristics of an electric motor (efficiency, rated operating current, speed, etc.), the most significant is power. Knowing the main data, you can:

• Select a thermal relay and automatic circuit breaker with suitable ratings.
• Determine the throughput and cross-section of electrical cables for connecting the unit.
• Operate the engine according to its parameters, avoiding overload.

We described how to measure the power of an electric motor in different ways. Use the one that is optimal in your case. Using any of the methods, you will select a unit that will best meet your requirements. But the most effective option, saving your time and eliminating the need to search for information and carry out measurements and calculations, is to keep the technical passport in a safe place and make sure that the data plate is not lost.

Determination by dimensions

Another way is to carry out measurements and calculations. Many of those who are interested in how to find out the power of a three-phase motor prefer it. You will need the following data:

• Core diameter in centimeters (D). It is measured from the inside of the stator. The length of the core is also required, taking into account the ventilation holes.

• Gross rotation frequency (n) and mains frequency (f).

Using them, calculate the polar division index. D multiplied by n and by Pi - let's call this reading A. 120 multiplied by f - this is B. Divide A by B.

As you can see, to calculate the value, it is enough to remember the school mathematics course.