What is the difference between installed power and rated power?

Rated active power of the electric drive

(
)
– this is the power consumed from the network at the rated load of the electric drive, at which it must operate for a long time in a steady state without exceeding the permissible temperature.

For long-term operating mode, the EP is equal to the rated value:

.

For receivers operating in intermittent mode, the rated power is determined from the nameplate power by bringing it to a long-term operating mode (PV = 1) in accordance with the formulas:

, or ,

where is the nameplate value, p.u.; – switching factor, calculated from the ED load graph, see formula (2.1).

For electric motors, the power consumed from the network is called connected power and is determined by the expression:

,

where is the rated power developed on the motor shaft, kW;

– nominal efficiency of the electric motor, p.u.

Rated reactive power of the electric unit

() – reactive power consumed by it from the network at rated active power and rated voltage.

For an electric device operating in a long-term mode, the value is calculated using the formula

,

where corresponds to the nominal ED (is the rated value).

For an electric device operating in intermittent mode, the value is calculated using the formula

.

Nominal apparent power

.

Example

Let's say we have a generator with a power rating of 3 kVA and cos φ equal to 0.8. In this case, the rated power of this installation will be equal to:

3 kVA x 0.8=2.4 (kW)

Now you can understand why power can be indicated in certain units of measurement, in watts (W) or Volt Amperes (VA). Some manufacturers, in order to save the consumer from the need to carry out calculations, simply indicate in the accompanying documentation both power values ​​- nominal and maximum. There are also options when the manufacturer indicates only one of the capacities and gives the value of the power factor. Some unscrupulous companies may hide the power factor from the consumer. This is done in order to pass off the generator as a more powerful unit than it actually is.

How to choose a vacuum cleaner based on suction power, or different power...

A vacuum cleaner is one of the most necessary household appliances that everyone has to buy at least once in their life. Many housewives dream of a stylish modern vacuum cleaner. So that it does not disappoint you when cleaning, you should focus not only on the price and design, but also on the technical characteristics, the main one of which is power.

Don’t be greedy and chase records: a powerful vacuum cleaner purchased “without looking” may unpleasantly surprise you when your electricity bills arrive. Let's together choose the best option that will ensure cleanliness in the house and save energy.

BELARUS-80.1/82.1

The tractor is designed to perform various agricultural work with mounted, semi-mounted and trailed machines and implements, and transport work. Environmental standard Stage II. Tractor BELARUS-80.1 - front axle. The BELARUS-82.1 tractor is a portal-type front drive axle with bevel gearboxes.

• home
• Products
• Tractors
• Basic model BELARUS-80.1

• Specifications

• Engine Stage 0 (D-243);
• Engine Stage I (D-243S);
• Reverse gear;
• Ballast weights for rear wheels;
• Front ballast weights;
• Metal-ceramic clutch linings;
• Speed ​​reducer;
• Power regulator ZNU;
• Combined towbar (hydraulic hook, drawbar, pendulum);
• Rear wheel doubling kit;
• Additional seat;
• Awning frame, awning base;
• Air conditioner;
• FDA with planetary helical gearboxes.

Aggregation

The three-furrow mounted plow PKMP-3-40R is designed for processing.

Three-furrow mounted plow PLN-3-35P (hereinafter referred to as the plow).

Taking into account the type of load

Household electrical appliances are characterized by two types of load:

• Active;
• Reactive.

The active (ohmic) load is consumed by devices that convert the received energy into heat. This is an electric stove, iron, hair dryer, air heaters, etc. The reactive load is consumed by other electrical appliances, which convert only a small portion of the energy into heat. The bulk of the energy consumed is used for another purpose. Examples of such appliances include a refrigerator, vacuum cleaner, TV, computer, etc.

If you need help choosing the generator power for your home, industrial workshop or any other facility, contact our specialists for qualified advice.

Mode – rated load – Great Encyclopedia of Oil and Gas, article, page 1

Mode – rated load

Page 1

The rated load mode for a heating turbine is the mode at which the power specified in the technical specifications for delivery is achieved, i.e. the greatest power that a turbine unit can develop for a long time at the generator terminals at nominal values ​​of thermal extraction of all main parameters (fresh steam, intermediate superheat, in extractions and in the condenser) and when using unregulated steam extractions for constant auxiliary needs of the power unit and with fully open control valves. [1]

In rated load mode (Fig. 22 6), the phase currents are equal to the rated current. [3]

The parallel excitation motor operates in rated load mode. [4]

Thus, the most economical mode is the rated load mode. This is true for all domestic power units. [6]

Determine the voltage on the field winding in rated load mode, if the inductive leakage resistance of the armature winding is Xa 0 31 Ohm, the resistance of the field winding is Rf 0 678 Ohm, the main inductive resistance of the armature winding, calculated without taking into account saturation, Xa 4 6 Ohm. [7]

The vibration characteristics of the pump are measured in rated load mode. The valve sets the pressure at the pump outlet corresponding to its rated capacity. Vibration is measured at three radial points located in the area of ​​the upper bearing of the pump and oriented at an angle of 120, and one axial point located on the valve flange. [9]

When moving from idle mode to rated load mode, the power factor increases from the cos value. With further increase in load, coscpj decreases slightly. [10]

When transitioning from idle mode to rated load mode, the power factor increases from the value sozf. With a further increase in load, sozf1 decreases slightly. [12]

Let us assume that the synchronous generator was operating at rated load, and then the load was completely dropped, but the rotation speed and field current remained unchanged. To determine this value, we will do the following (Fig. 16.14): in the same coordinate axes we will construct the characteristics of no-load and short circuit. [13]

Features of electric drill engines are high slip in the rated load mode and a significant starting torque, reaching (1 2 – il 7) MH. The choice of such a characteristic is due to the desire to provide the maximum possible starting torque, accompanied by a small multiplicity of the starting current. [14]

The change in generator voltage is characterized by an increase in voltage during the transition from rated load mode to no-load mode, related to the rated voltage (Fig. [15]

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Calculation of basic engine parameters from the nameplate

Electric motors are found everywhere in industry and everyday life. If you haven’t paid attention, I’ll give you a couple of photo examples:

Sometimes a need arises, born of everyday curiosity, or a production need, to determine the power of an electric motor by its appearance, or the permissible operating temperature, not to mention the current and voltage values.

Here it is possible that the plate on which the nominal parameters are written has been torn off, or the nameplate is in such a state that it is impossible to distinguish anything. How to be in such a situation...

It’s one thing if you’ve worked in engine production all your life and can determine the power by eye. In other cases, a ruler (tape measure) and tables with the dimensions of the mechanisms will help determine.

If your activity lies more in theoretical research than practical, then a formula for determining the power of an electric motor or a table with nominal data will be useful, this is exactly what this article is about and not only.

Electric motor label

Having examined any electric motor, with rare exceptions, you can find a plate screwed onto bolts, screws or rivets. What is written on this piece of metal? Let's take a nameplate, replacing the serial number on it with the name of the site.

By the way, it rarely happens that a plate for electrical equipment is in such almost perfect condition. Often the data is faded or covered with paint, because the task is for the maintenance personnel to paint the engine, and not to paint the engine, leaving the plate untouched. But we were lucky. Let's go in order.

First line

- number of phases and type of current (3

), serial number, network frequency, design and installation form, insulation class

Second line

— type of electric motor, cosine phi, possible connection diagrams, rated speed

Third line

- possible rated voltages, rated power, IP - degree of protection of the electric motor, weight, operating mode of the electric motor (S1).

Fourth line

- rated currents depending on the winding connection circuit, then which guest the ed corresponds to.

Let's look at the individual parameters in more detail.

Electric motor power: total, active and shaft

Formula for calculating the power of a three-phase asynchronous motor:

S1 - total power consumed by the motor from the network

P1 - active power consumed by the electric motor from the network (indicated on the nameplate)

P is the active power on the EM shaft.

cosf - cosine phi, power factor - phase angle between active (P) and total power (S).

In the formulas above, the power value is obtained in W, the total power value in VA. To convert to kilowatts, you need to divide the resulting value by a thousand. The value of current and voltage, respectively, in the formula above is in amperes and volts.

I1 and U1 are linear values ​​of current and voltage, they are also called phase-to-phase. Not to be confused with phase ones. Linear ones are AB, BC, SA (380); phase - AO, VO, SO (220). If we express the power formulas in terms of the phase values ​​of current and voltage, then instead of the root of three there will initially be a coefficient of 3. This coefficient is determined visually through the vector diagram of the three-phase voltage.

For DC motors, the formula will simply be the voltage at the motor terminals multiplied by the current drawn by the motor from the network.

Power consumption p1 is greater than the power on the EM shaft due to losses that arise when converting electrical energy into mechanical energy.

Star/Delta and 220/380, 380/660

See all the values ​​in order as they go through the fraction. That is, it is written on the nameplate Y/D (triangle/star), which means that the currents and voltages will accordingly be first for Y, and after the fraction for the star. The only caveat is that at 220/380 the triangle will be 220, and at 380/660 the triangle will be 380. That is, to say that 380 is always a star is incorrect.

Always read the label on the engine before connecting.

The advantages of star and delta connections are abstract, since each circuit has its own areas of application:

• Y - less operating and starting current, more voltage, less starting torque, less heat
• D - higher starting torque, starting current, but also heats up more.

There are two-speed engines, where they first start on a star, and then switch to a triangle. In this case, the mechanism starts up easier and then works with more power.

When connecting a three-phase 220V motor, where there is only a phase and a zero, you can resort to a circuit with capacitors.

Execution form and installation method

IM 1081 - form of execution and installation method in accordance with GOST 2479 and IEC60034-5. In our example, this means “foot-mounted with two end shields, with one cylindrical shaft end.”

This name consists of the Latin letters IM and four numbers.

The first digit from 1 to 9 is a constructive method of execution

Second and third (00.99) - installation method

The fourth (0..9) is a symbol for the end of the shaft.

Electric motor efficiency

Efficiency shows the efficiency of an electric motor’s conversion of electrical energy, which it takes from the network, into the mechanical energy of rotation of the mechanism.

If there were no losses during energy transmission, then the efficiency would be 100%. However, this does not exist. However, there are types of losses that reduce the value of the coefficient:

• losses from heating current-carrying conductors with increasing load - electrical losses
• losses due to eddy currents, hysteresis in laminated stators - magnetic losses
• friction losses of bearings, ventilation - mechanical losses
• plus various additional less important types of losses.

Often, but not always, the higher the rotational speed of an electric motor, the greater its efficiency. This is due to the dependence of efficiency and ED slip. There are classes according to the efficiency value according to GOST IEC/TS15: IE1, IE2, IE3, IE4.

Motor insulation classes based on heat resistance

Here GOST 8865-93 will come to our aid. The insulation class of electrical machines characterizes the maximum temperature at rated parameters. That is, in our example, with the nominal data from the plate, the insulation temperature should not exceed 155 degrees.

I will provide data on the permissible temperatures of electric motors for different insulation classes. Please note that materials may have different classes.

• Y - 90
• A - 105
• E - 120
• B - 130
• F - 155
• H - 180

Next come the digital classes: 200, 220, 250 - and after them plus 25 degrees with a class designation according to the permissible temperature value.

These temperatures were determined empirically when operating at nominal parameters throughout the service life to values ​​at which the tangent delta increases and the breakdown voltage decreases.

How to calculate what kind of generator you need for your home?

If you ask yourself how much generator power is enough to vacuum the house while the light is on and the refrigerator is on, let’s calculate:

1. So, if the power of the vacuum cleaner is 1500 W, and its inrush current coefficient is 1.5, then we calculate:
2. 1500 W x 1.5 = 2250 W - this is how much the vacuum cleaner needs to start.

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