CN1558535A - A wound rotor induction motor - Google Patents

Abstract

The invention discloses a wound rotor induction motor. Three-phase AC pole-changing windings with two pole numbers are arranged on the stator. One pole number q is used for starting, and the other pole number p is used for normal operation. The working state of the number of poles is switched by a switch device; two kinds of multi-phase symmetrical windings with poles are also arranged on the rotor. For the number of starting poles, the rotor winding presents a higher resistance to the stator. For the number of poles in normal operation, the rotor winding Presents a lower resistance to the stator. The rotor circuit of the present invention does not require any additional starting resistors to be connected in series, but it has both low starting current and high starting torque as the common wound induction motor with slip ring brushes, can start with full load, and has more High reliability and operating efficiency. Its start-up and running state conversion is carried out through the pole-changing switching of the stator winding, so there is no need to install a slip ring on the rotor, which not only simplifies the mechanical structure of the rotor, but also eliminates the hidden trouble caused by it, and improves the operating efficiency.

Description

A wound rotor induction motor

technical field

The invention belongs to the field of electric motors, in particular to a winding rotor induction motor. It is a pole-changing start-up non-slip ring brush wound rotor induction motor.

Background technique

According to the principles of electromechanics, the size of the induction motor rotor resistance has a decisive influence on its starting and running performance. If the rotor resistance is small, the loss is small, and the efficiency is high during normal operation, but at this time, the starting performance is not good, the direct starting current is large (5 to 7 times the rated current), and the starting torque is not large. On the contrary, the rotor resistance is large and the starting performance is good, which can reduce the starting current and increase the starting torque, but at this time it will lead to low efficiency during normal operation, and the two cannot be balanced.

The usual way to solve the above problems is to use a wire-wound induction motor with a slip ring brush, which is characterized in that an appropriate starting resistor is connected in series in the rotor circuit when starting, which not only reduces the starting current but also increases the starting torque. After the starting process is completed, Cutting off the starting resistor can also ensure high efficiency during normal operation, so that both can be taken into account.

However, due to the sliding contact in the rotor circuit of the ordinary wound induction motor, which is easy to fail, and the starting resistor must be connected in series to start smoothly, the rotor structure is complicated, the reliability is low, and maintenance is difficult, which will make the actual operation efficiency decreases.

purpose of invention

The object of the present invention is to provide a wound rotor induction motor, the rotor of which has a simple structure, high reliability, easy maintenance and improved efficiency during actual operation.

A wound rotor induction motor provided by the present invention includes a stator and a rotor, and is characterized in that three-phase AC pole-changing windings with two pole numbers are arranged on the stator, one of which is used for starting the pole number q, and the other The number of poles p is used for normal operation, p≠q, and the two working states of the number of poles are switched by the switch device; the rotor is also arranged with multi-phase symmetrical windings with two poles, and, for the number of starting poles, the rotor winding is The stator presents a higher resistance to the stator and the rotor winding presents a lower resistance to the stator for the normal number of operating poles.

The basic unit formed by the windings of each phase of the above-mentioned rotor is a composite coil, and the composite coil is formed by parallel connection of two sub-coils with different numbers of turns arranged in the same rotor slot.

The structure of the composite coil is as follows: a total of N ₂ conductors are arranged in the rotor slot, which are divided into two parts N ₂₁ and N ₂₂ , and N ₂₁ and N ₂₂ /2 are connected in series to form a turn number of N ₂₁ +N ₂₂ / 2 multi-turn sub-coil, and the remaining conductors form a small-turn sub-coil with N ₂₂ /2 turns, and the two sub-coils with different turns are connected in parallel.

The rotor circuit of the present invention does not require any additional starting resistors to be connected in series, but it has both low starting current and high starting torque like the common wound induction motor with slip ring brushes, and can start with full load, and has more advantages. High reliability and operating efficiency. The switching between starting and running states of the present invention is carried out through the pole-changing switch of the stator winding, so there is no need to install a slip ring on the rotor, which not only simplifies the mechanical structure of the rotor, but also eliminates the hidden trouble caused by it, and improves the operating efficiency.

Description of drawings

Fig. 1 is a schematic diagram of the composition principle of the composite rotor coil of the present invention, in which  represents the current flowing in, ⊙ represents the current flowing out, and -------- represents the path of the magnetic force line of the slot leakage; (a) is the arrangement in the conductor slot, ( b) is a composite coil;

Fig. 2 is a schematic diagram of connection of three-phase rotor compound coil windings of the present invention;

Figure 3 is a schematic diagram of the wiring of the 96-slot composite coil winding of the rotor of the present invention, note: Indicates a multi-turn sub-coil,

—Indicates a few-turn sub-coil.

Detailed ways

A set of three-phase pole-changing windings with two poles is placed on the stator of the present invention, one pole number q is used for starting, and the other pole number p is used for normal operation (P≠q), and a switch device is used Switching different numbers of poles is used to switch between the two working states of starting and normal operation. There are also multi-phase symmetrical windings with two kinds of poles arranged on the rotor. Corresponding to the number of poles q at startup, the rotor automatically presents a high resistance. At this time, the starting current can be reduced and the starting torque can be increased; The number of poles p, the rotor presents low resistance, and will have high operating efficiency at this time.

As mentioned above, the stator of the present invention can be an ordinary three-phase pole-changing winding with two poles, and for these two poles, the rotor of the present invention must present different resistance values respectively. The key to realize this is to adopt the following The specially designed rotor windings.

In the present invention, the rotor presents higher resistance to the stator when starting, but at the same time it also requires that the rotor leakage reactance does not increase accordingly, so corresponding to the number of poles q, the concept of "non-inductance" that weakens the rotor reactance is used, and the corresponding poles in normal operation p, on the contrary, requires the rotor to present a lower resistance to the stator.

An example is given below to make the rotor meet the above two requirements of the stator at the same time. The present invention refers to the basic unit constituting the following winding as "composite coil", and the specific description is as follows.

See Figure 1. In the rotor slot shown in Fig. 1a, there are N ₂ conductors arranged in total, which are divided into two parts N ₂₁ and N ₂₂ . Among them, the conductors with opposite currents inside N ₂₂ appear in pairs, and the slot magnetic potentials generated cancel each other out, even if the total leakage reactance of the rotor is weakened, this part of the conductor is called "non-inductive conductor", which will only be used in the rotor circuit Acts as a pure resistor. The specific connection when the N ₂ conductors form a coil is that N ₂₁ and N ₂₂ /2 are connected in series to form a multi-turn sub-coil with a number of turns of N ₂₁ +N ₂₂ /2, and the remaining conductors form a number of turns A few-turn sub-coil of N ₂₂ /2, these two sub-coils with different numbers of turns are connected in parallel to form a "composite coil", as shown in Figure 1b.

It can be seen from Figure 1b that this "composite coil" composed of two sub-coils with different numbers of turns can also form a closed circuit inside when the two ends of a and b are not connected. Because the induced potential of the coil is proportional to the number of turns, the induced potentials of two sub-coils with different numbers of turns in the air-gap magnetic field are E ₂₁ +E ₂₂ /2 and E ₂₂ /2 respectively. According to the reference direction shown in Figure 1b, along the In the inner closed loop, the potentials generated by the two sets of conductors contained in the turn N ₂₂ cancel each other out, but the potentials generated by the turn N ₂₁ cannot cancel each other out, thus causing a current I _c in the loop. For the two sub-coils arranged in the same slot, the current flows in the opposite direction, so the magnetic potential generated by the coil N ₂₂ also cancels each other out, and only the coil N ₂₁ in the composite coil can generate effective magnetic potential . At this time, if K _p = N ₂ /N ₂₁ , and the rotor resistance converted to the stator side of the conventionally connected wound motor when the number of conductors in the rotor slot is N ₂ is r ₂ ′= r ₀ , then the non-inductive winding is used Or the rotor resistance converted to the stator side will increase to ${\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20041001267900071.png"\; state="\{\{state\}\}">r</figure-callout>}}_2^{\&prime;}=K_{\mathrm{\&rho;}}^2{r}_0.$

It is worth noting that while the conversion value of the above-mentioned rotor resistance increases, the rotor leakage reactance will not increase due to the effect of "non-inductance". It can be proved that this is also equivalent to the increase in the resistivity of the rotor conductor from ρ When it reaches K _ρ ² ρ, it also shows that all kinds of high-resistivity conductive materials that had to be used in the past to achieve the purpose of increasing the rotor resistance can be adjusted by using only one conductive material if the above-mentioned "non-inductive" principle is adopted. It is also achieved corresponding to the K _ρ value.

The multi-phase winding of the rotor in the practical application of the present invention is composed of the above-mentioned composite coils. The following takes the three-phase winding as an example to illustrate its connection principle.

所示，这和标准三相60°相带绕组相同，显然，这时转子将对定子呈现低电阻；对于起动极q，由于转子绕组是按运行极p标准60°相带连接各个复合线圈，因此，对应起动极q，转子绕组感应的相电势(对p极而言的相绕组)为零，这时当然也不存在对于起动极q而言的相电流，这也即相当于图1b中所示复合线圈a、b两端不连接，复合线圈将如前所述其内部自成闭路而产生环流，各个复合线圈的流通路径分别如图2中 (以a相为例，其余两相同，这里k＝1…n)所示，这时转子将呈现高电阻。The three-phase rotor winding shown in Figure 2 is a standard 60° phase belt winding for the normal operating pole p, and a multi-phase winding for the starting pole q, and the current flow paths of the two poles are also Each is different, and Fig. 2 marks the flow paths of magnetic field induced currents corresponding to different numbers of poles in the two cases of start-up and normal operation respectively. For the normal operating pole p, the three-phase current flow path of the rotor winding a, b, c is shown in Figure 2

As shown, this is the same as the standard three-phase 60° phase belt winding. Obviously, the rotor will present low resistance to the stator at this time; for the starting pole q, since the rotor winding is connected to each compound coil according to the standard 60° phase belt of the running pole p, Therefore, corresponding to the starting pole q, the phase potential induced by the rotor winding (phase winding for the p pole) is zero, and of course there is no phase current for the starting pole q at this time, which is equivalent to The two ends of composite coils a and b shown are not connected, and the composite coil will form a closed circuit inside itself as mentioned above to generate a circulating current. The circulation paths of each composite coil are shown in Figure 2. (Take phase a as an example, the other two are the same, here k=1...n), the rotor will present high resistance at this time.

Due to the different numbers of poles used in the normal operation and the starting state, the synchronous speed of the two poles is different, so the speed of the present invention cannot reach the normal running speed when starting, and there will be a certain inrush current when the starting state is converted to the running state. Minimize its influence as much as possible, and the difference between the two pole numbers should not be too large. Generally, the suitable range of application is the ratio of near poles, such as 8/10 poles or 10/12 poles in the above example.

An example of the present invention is as follows.

For a motor with 96 slots in the rotor, the number of poles in normal operation is p=8, and the number of starting poles is taken as q=10. The three-phase winding of the stator is a conventional single-winding pole-changing winding, and the rotor winding is composed of the aforementioned composite coils. The specific wiring method is shown in Figure 3. It can be seen from Fig. 3 that for the 8-pole winding in normal operation, the winding is equivalent to 24 phases, the phase bandwidth is 15°, and the winding distribution coefficient is 1.0. Its performance index is equivalent to that of the normal standard 8-pole winding. Low resistance, at this time will have high operating performance; for 10 poles at start, the winding is a compound coil characteristic, which can present high resistance to the stator, so it can have good starting characteristics.

Claims (3)

1, a kind of wound-rotor induction motor, comprise stator and rotor, it is characterized in that, be furnished with the three-phase alternating current variable-pole winding of two kinds of numbers of poles on the stator, wherein a kind of number of poles q is used for starting, another kind of number of poles p moves as normal, p ≠ q, and two kinds of number of poles operating states adopt switching devices to switch; Also be furnished with the heterogeneous symmetric winding of two kinds of numbers of poles on the rotor, and to the starting number of poles, the rotor winding presents high electrical resistance to stator, to normal operation number of poles, the rotor winding presents than low resistance stator.

2, motor according to claim 1 is characterized in that: the elementary cell that each phase winding of described rotor constitutes is a compound coil, and compound coil is formed by the different subcoil connect in parallel of two numbers of turn that is arranged in the same rotor.

3, motor according to claim 1 and 2 is characterized in that: the structure of described compound coil is: be furnished with N in the rotor altogether ₂The root conductor divides and makes N ₂₁With N ₂₂Two parts, N ₂₁With N ₂₂/ 2 are in series, and forming a number of turn is N ₂₁+ N ₂₂It is N that/2 multiturn subcoil, remaining conductor then form a number of turn ₂₂Few circle subcoil of/2, the subcoil connect in parallel that these two numbers of turn are different.

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