SU1690104A1 - Double feeding machine power drive - Google Patents

Abstract

This invention relates to electric machines controlled by a frequency converter in a rotor circuit. The goal is to reduce the cost. The dual-feed machine contains a main asynchronous motor 1 with a phase rotor, the rotor windings of which are connected to a power generation unit, which is made of two additional asynchronous machines 2 and 3 with a phase rotor of different polarity, rigidly connected by shafts, and a controlled thyristor frequency converter in the rotor circuit . In this case, the stator windings of the asynchronous machine 2 of smaller polarity are connected to the rotor windings of the main motor 1 and the asynchronous machine 3 of the greater polarity is connected to the supply mains by the stator windings, and the rotor windings of these machines 2 and 3 are connected to reverse phase alternation and connected to the controlled thyristor frequency converter. The ratio of the poles of machines 2 and 3 is chosen greater than the maximum slip of the main asynchronous motor 1. This reduces the cost when using a dual-feed machine to control the speed of an asynchronous machine with a phase rotor. 1 il. (L with

Description

The invention relates to electric machines controlled by a frequency converter in the rotor circuit.

The purpose of the invention is to reduce the cost.

The drawing shows a diagram of an electric drive with a dual-power machine in conjunction with other elements of the device.

An electric drive with a dual-power machine consists of a main standard asynchronous motor 1 with a phase rotor, as well as two additional standard asynchronous machines 2 nd 3 with a phase rotor, respectively, on pi and rg, the number of poles and a controlled frequency converter 4. The stator windings of the asynchronous machine are connected to the rotor windings of the main motor 1, the stator windings of the machine 3 are connected to the mains. The shafts of additional asynchronous machines 2 and 3 are rigidly connected, and the rotor windings are connected one to the other with reverse phase rotation, connected to a frequency converter 4 controlled by a regulator 5, connected to a speed sensor 6 of the main motor 1. The frequency converter 4 is supplied from a transformer 7 .

Two asynchronous machines 2 and 3; the frequency converter 4 in aggregate is an electromechanical frequency converter (EMF).

An electric drive with a dual-power machine operates as follows.

If the sliding energy of the main engine 1 is removed from the rotor, then the additional machine 2 with the phase rotor operates in the motor mode, and the machine 3 - in the generator mode. In this case, from the sensor 6 of the rotational speed of the rotor of the main engine 1, as well as from the sensor 8 of the mains frequency, signals are input to the inputs of the controller 5, which controls the frequency converter 4. Since the machine 3 operates in the generator mode, and the rotational speed of its rotor does not correspond to the synchronous network frequency, the current frequency of the three-phase rotor winding f _{s of the} asynchronous machine 3 is formed by the regulator 5 in the form of the difference between the frequency of the industrial network and the rotor speed. Additional asynchronous machine 2 will operate at speeds above synchronous in motor mode, and machine 3 - at speeds below synchronous in generator mode. Thus, the EMF, consisting of two asynchronous motors with a phase rotor and a controlled frequency converter, converts and transforms the slip energy of the main motor into a network.

For the AC machine to operate in steady state, it is necessary that the MDS of the stator and rotor are mutually stationary in space. This condition for asynchronous machine 3 is written as follows:

ωι = ω + &) f, (1) where ωι, al is the angular velocity of the voltage and current vectors, respectively, of the stator and 15 rotors;

ω is the angular velocity of the rotor.

Because

(2) where.fi is the network frequency;

η and rg - rotor speed and the number of poles of an asynchronous machine 3;

fs is the current frequency of the rotor winding of machine 3, then relation (1), taking into account (2), will have the following form;

fl = P2P + fs.

(3)

Conditions immobility MDS stator and rotor in the space for asynchronous machines with 2 Given that the rotor winding 35 _is connected to the second machine inverse alternating phases, and the stator windings are connected to the rotor windings of the main motor, the following equation:

sfi = pin-fs, (4) where s and pi are the slip of the rotor of the main motor and the number of poles of the asynchronous bus 2.

From relations (3) and (4), the frequency of the current of the rotor windings of asynchronous machines 2 and 3 for the case when the slip energy is removed from the main motor is: _{= f} . Pl / P2 S ^s 1 + Pj / P2 (5)

In expression (5), it is necessary to select the 55th polarity of additional asynchronous machines from the condition pi / pr> s, so that the frequency has a positive value, and s is the maximum slip of the main motor.

If the main machine 1 is in dual power mode, i.e. the energy from the network is supplied to the rotor circuit using the EMF, then the additional asynchronous machine 3 operates in the motor mode, and the 5 asynchronous machine 2 in the generator mode. In addition, from the sensor 6 of the rotational speed of the rotor of the motor 1 and from the sensor 8 of the mains frequency, signals are also sent to the inputs of the controller 5, at which the frequency 10 of the current in the stator winding of the asynchronous machine 2 is equal to the frequency of the current of the rotor of the main motor 1. In this case, the EMF will transform and convert the voltage of the industrial network to a voltage of another frequency equal to the frequency of the current of the rotor circuit of the main motor. Then the immobility condition of the MDF of the stator and rotor windings for asynchronous machines 2 and 3 is written as follows: 20

sf 1 = pm - f _s ; (6) fl = Ρ2Π + fs. (7)

The joint solution of equations (6) and (7) gives the frequency of the current in the rotor circuit for the case when the energy is supplied to the main motor fs “fl

P1 P2 - s + Pl / P2 '(8)

Thus, the current frequency of the rotor winding of additional asynchronous machines, regardless of whether the energy is supplied or removed from the rotor of the main motor, is determined by the same expression. by (5) or (8). Therefore, the rotor windings of these machines can be connected to a 40 controlled frequency converter.

The sliding power of the main engine is determined by the following formula:

p ₃ = spi, where pi and s are the active power and slip of the main engine. Considering that this power is converted by an additional 50 asynchronous machines 2 and 3, the RPM power of these motors should be equal to the sliding power of the main motor, i.e.

PAon = Ps = spi. (9) .55

Similarly, the power of the frequency converter included in the rotor circuit of the additional machine will be equal to

Ртп = S Рдоп, (10) where s' is the slip of the rotor of the additional machine.

This slip can be defined as follows:

fs _ ρι / ρ2 - s fi 1 + ρι / ρ2 ’

If indicated by

Pi y = -. then power P2

P ™ ~ \ 'R ° ° ⁿ · (12)

Given the expression (9), the capacity of the frequency converter relative to the power of the main motor is determined

Ρτη = δ ^ · ρΐ. (thirteen)

From the expression (13) it is seen that the power of the thyristor frequency converter included in the rotor circuit of the auxiliary machine is much less than the power of the thyristor frequency converter (TFC) included directly in the rotor circuit of the main engine. You can determine the coefficient of decrease in power TFC

Kpch - (1 + s) / (y ~ S).

For the speed range of the main engine, the slip s = 0 - 0.3, and for pi = 2, p2 = 6, the coefficient of reduction of the TFC is

+0.3

2/6 - 0.3 "39.

As can be seen from the calculation, the power of the TFC included in the EMF is ten times less than the power of the TFC included directly in the rotor circuit of the main engine, which ensures a reduction in cost, since the TFC is 7-10 times more expensive than an engine of the same power. For TFCs of lower power, operating costs are reduced.

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Claims (1)

Claim An electric drive with a dual-power machine, containing the main asynchronous motor with rotor windings and a controlled frequency converter, characterized in that, in order to reduce the cost of the electric drive by reducing the power of the controlled frequency converter, it is equipped with two asynchronous machines with a phase rotor of different polarities pi and rg while the stator windings of an asynchronous machine with a p-ι number of poles are connected to the rotor windings of the main induction motor, the stator windings of an asynchronous machine with rg chi poles scrap intended for connection to the mains, the rotor windings of asynchronous machines conversion unit interconnected with opposing alternating phases and connected to a controllable frequency converter, wherein the ratio of the numbers of poles pi / p transducer asynchronous machines greater than the maximum core induction motor slip. Compiled by I. Ilyin Editor N. Tupitsa Tehred M. Morgenthal Corrector M. Sharoshi Order 3822 Circulation Subscription VNIIIPI State Committee for Inventions and Discoveries under the State Committee for Science and Technology of the USSR 113035, Moscow, Zh-35, Raushskaya nab ,, 4/5 Production and Publishing Combine Patent, Uzhgorod, 101 Gagarin St.