FI119135B - A synchronous machine - Google Patents

Description

1,119,135

CYCLE MACHINE

The invention relates to a synchronous machine according to the preamble of claim 1.

AC drives controlled by AC drives have become more common in industrial applications. Due to their control characteristics and the clarity and cost-effectiveness of their implementation, they have also become a real option in industrial line drives. The controlled use of three-phase electric motors is increasingly based on the use of AC drives. The availability of low-cost permanent magnets has replaced the previous controlled asynchronous motor drives with a permanent magnet magnetized synchronous machine, which has the technical advantages of being a large continuous torque while still remaining low at low speeds. There is no fundamental difference in frequency converter operation whether the electric machine acts as a motor or a generator, whereby the electric machine brakes as long as the braking energy is handled appropriately. The frequency converter drive motor is a single speed motor and the speed is set by the frequency converter.

In large-scale processes, it is cost-effective to supply multiple AC drives from the same power system. Both asynchronous and permanent magnet synchronous drive drives can be connected to the system. For maintenance, the individual drives can be distinguished from the common DC system. Maintenance is always disconnected from the DC system. In the prior art, the ··· * .. outputs of the frequency converters controlling permanent magnet synchronous machines are provided with disconnectors which are opened when servicing the control devices, as described below with reference to FIG. Such an implementation is known, for example, from the conference publication 'Safety Aspects of Permanent Magnet Motors in Paper Machine Applications', by Tero Huhtanen, • * ·

Ilkka Erkkilä; IEEE Pulp & Paper Conference Victoria, Victoria Island, BC, Canada 2004-:: V 06-27 .... 2004-07-01.

• · · · · · · · ·

In applications with AC motors, there will be situations in various applications where: 25 the electric motor is disconnected from the mains and / or motor controlled power supply such as ··· the drive, but at the same time the motor is rotated by mechanical load. of. Industrial line drives, for example, have large masses and rolls that cannot be stopped immediately. If the electric motor rotates due to the load acting on the shaft and the motor magnetisation is active, a voltage is generated in the motor windings. Then the motor • ··! . The terminals on the 30 market may have a voltage equivalent to the operating voltage, even if the drive is · · switched off.

2,119,135

In synchronous machines, voltage is generated on the poles if the machine is excited. If the magnetization of the synchronous machine is implemented by electromagnets, the magnetization is generally adjustable and can also be switched off in a suitable manner when the supply voltage is cut off. In a Kestomag-neted synchronous machine, the situation is problematic because the magnetization is always on and the stator winding of the synchronous machine generates an electromotive force as the machine rotates. When the motor is switched off, it is a common assumption that no voltage is present at the terminals of the motor and the inverter supplying it. Service and operating personnel often need to work in the area where the machinery is located, which may result in unintentional contact with hazardous voltage. In addition, there are situations where the 10 self-rotating mechanical rollers are separated from the engine by a wall or wall, whereby the personnel are not directly aware of the hazard.

Voltage is always induced in the stator winding of a three-phase electric machine magnetized with permanent magnets, a synchronous machine, when the rotor rotates. Several percent of the rated voltage is already induced at low rotation speeds when mechanically connected whole units are moved.

Said voltage can be harmful or even dangerous when the drive is stopped or other checks on the electrical controls are performed while the machine is stopped and the rotor rotates for uncontrolled reasons. Voltage can directly affect personal safety or prevent maintenance due to the risk of component damage. The drawbacks are realized especially in installations which are so large that electric drive components, the motor, control devices such as the drive with auxiliary components and motor cables are far apart, typically in different rooms, especially the motor and the controls. • Well • · • · "I many industrial processes and other large controlled processes require the described location of equipment • ♦ · III. In this case, it is not always possible to reliably control the movement of the machine assembly parts • # 25 or their movement or the engine rotation with the moving parts.

· · 3 119135 either as a result of a fault or by stopping the drive. The prior art provides only a half solution to this problem with the synchronous machine.

The adverse effects of the voltage described above in the control apparatus can be overcome by prior art supplementary parts of the drive in the same switchgear at the starting point of the motor 5 cable, such as an output isolator, a three-phase winding short circuit, particularly polarized or earthed.

The latter two methods can cause considerable machine warming, depending on cooling, if the unintentional rotation of the rotor continues for a longer period of time as the winding typically carries a nominal current. The winding short circuit and site earthing are implemented according to the prior art as a structural combination with an output isolator.

It is an object of the present invention to provide a solution that eliminates harmful and dangerous voltages at motor terminals when the permanent magnet motor is disconnected from the supply source and it is possible for the motor to continue to rotate. To accomplish this, the invention is known from the features of the characterizing part of claim 1. Other preferred embodiments of the invention are known from the features defined in the dependent claims.

In accordance with the invention, the motor itself is coupled so that the motor's ability to supply • · • · · current when rotating the rotor remains very low and the pole voltage is substantially zeroed.

• mukais ···: 20 The solution of the invention eliminates the undesirable effects of electric * ... * motor force induced on the stator windings when the rotor rotates when the synchronous machine is disengaged m • ♦ ♦ M. ' of the drive inverter. The partial windings of the stator winding of the synchronous machine ··· • · * ··· * are connected so that no harmful or dangerous voltages are present at the winding terminals.

The stator winding of the synchronous machine is divided into sub-windings which can be combined such that the phase winding and its effect correspond to the normal operation of the machine and that the sub-windings • · · · are substantially zero.

• · · • · • * · «·

According to some preferred embodiments of the invention, the partial windings of each step are in normal operation with each other in Saija, and the partial windings are wound in the same direction, whereby · · · ii> <; their cumulative effect is the sum of the effects of the share windings. When the partial windings are interconnected according to the invention, the voltages induced in the partial windings cancel each other out, and the voltage seen at the external connections of the machine is substantially zero.

According to another preferred alternative, in normal operation the partial windings are connected in parallel so that they magnetize in the same direction. When the machine is disconnected from the supply source, the sub-windings are disconnected in series such that the voltages induced on them cancel each other out so that substantially zero voltage is applied to the terminals of the machine.

In a preferred embodiment, the switching device is remotely controlled and timed according to frequency converter control. In addition, the auxiliary contact of the drive-side isolator can also be connected to the control of the switchgear. This ensures that the rear-10 converter is reliably disconnected when the synchronous machine switches are in the rest position. The separator operating lever may preferably be individually lockable.

According to another embodiment, the switching device is locally controlled so that the desired control can be made by the local control. The control energy of the coupling device continues to come from the control device.

In the third embodiment of the coupling device, the control method is local and mechanical. Information about the position of the switching device can also be exported to the control device.

The invention will now be described in detail with reference to the accompanying drawings, in which: - FIG. 1 shows a diagram of a line drive, which is an embodiment of the invention, FIG. a switching scheme according to the invention, • · ··· ♦ M. * 20 - Figure 3 shows another switching scheme according to the invention ··· • • · · ** - Figure 4 shows a third switching scheme according to the invention and • · · · · · Figure 5 shows a fourth switching arrangement according to the invention.

♦ m ···: [: The line operation of the industrial plant consists schematically of the system of Figure 1. The DC bus 2 is fed from the mains 4 via the rectifier 6. The rectifier M 25 is disconnected from the supply network by a switch 8. Several DC motors 10 are connected to the DC bus, which are controlled by the inverters 12. The inverters 12 can be separated from the DC 2 by the switch 14 and the switch 10 by the switch 16.

5,119,135

Line drive motors 10 may be mechanically disconnected or clamped to each other, depending on the application. Although the motors are separate, their shafts are often coupled to a mechanical load with a high rotating idle mass. The opening of the circuit breakers 14 and 16 thus does not prevent the motor from rotating, whereby the disconnected motor windings induce an electric motor force at a speed dependent frequency.

In the following, the solution according to the invention will be described with a permanent magnet magnetized synchronous motor, where the stator winding is three-phase and the winding of each phase consists of two substantially identical partial windings. The stator windings are connected to either a star or a triangle and the partial windings are normally connected to either Saija 10 or to each other in parallel. In all cases, the stator winding is normally connected to the motor mains terminals. In addition, the ends of the coils are connected to the switch contacts.

In the present embodiment of the invention, the motor phase windings are formed of two sub-windings which, in normal operation, magnetize in the same direction. The ends of the partial windings 15 are connected by wires to switches which, when in the active position, operate the motor in normal mode. When the switches are rotated, the partial windings engaged in the resting position are rotated so that the electromotive forces induced in them are compensated in stages. Preferably, the switches are located in a motor junction box or other location outside the engine accessible to a service technician. Because of the induction voltage applied to the coils by permanent magnet motor • · * ·: “20” when the motor is running, the use of the reset switches must be supervised and prevented from being fitted in normal operation.

• · · • · ·

Figure 2 illustrates an embodiment of the invention in which the voltage (s) induced in the windings at the motor terminals is eliminated. The stator winding of the motor is connected to a triple • · »ϊ ,, and each phase winding U, V and W is made of two sub-windings Upi and UP2, and 25 Vpi and VP2 and Wpi and WP2 respectively. The winding directions are indicated by the black dot on the other end of the coil in a commonly known manner. The coils Upi and UP2 are coiled • · ·: ... * in the same direction. When the switches K1, K2 and K3 are in the rest position, the switch contacts are in the position shown in Fig. 2, and the partial windings Upi and UP2 are connected in series with their center "· *. Due to the reverse winding direction, the voltage applied to the partial windings. opposite, even though they are pierced by a parallel magnetic flux, ·; ··; and thus the voltage across the terminals L [and L2 of the entire phase winding U is zero, respectively, corresponding to the phase windings Vpi and VP2 and phase windings WP1 and 6119135

The voltages induced by Wp2 cancel each other out so that the visible voltage at all terminals L1, L2 and L3 is zero. When the switches K1, K2 and K3 are turned to the active position, the sub-windings are parallel connected and magnetize in the same direction, and the voltage applied to them is parallel. The engine will then be in normal operating condition.

Figure 3 illustrates a situation in which a single-phase winding consists of two sub-windings which, in normal operation of the synchronous machine, are connected in series. The two phase windings of the phase, such as Upi and UP2, are wound in the same direction so that their magnetic effect is parallel when the reset switches Κι, K2 and K3 and Ki 'and K3' are in the active position. When disconnecting the motor from the mains or power supply 10, turn the switches Κι, K2, and K3 to the rest position so that the switch contacts are in the positions shown in Figure 3. The partial windings of each phase are connected in series and the voltage across the entire phase winding is zero. Similarly to Fig. 2, the applied voltage at terminals L1, L2 and L3 of the machine is zero.

In the case of a residual motor, the windings are connected as shown in Figures 4 and 5. Figure 4 shows the connection when the single-phase windings are parallel to each other while the machine is in normal operating mode. When the switches Κι, K2 and K3 are rotated to their rest position, the phase windings as shown in Fig. 4 are in series with each other, whereby their total electromotive force at the machine terminals is zero due to the opposite winding direction of the phase windings.

······· * * ": 20 In the case of Fig. 5, the phase sub-windings are normally connected in series with * · · V: the switches Κι, K2 and K3 are in the active position. In this case, their winding direction is the same and φ · * ·. The Kim switches are turned to the rest position according to Fig. 5, the voltages induced in the partial windings affect the opposite direction - * ... *, and the voltage displayed on the terminals L1, L2 and L3 of the machine is zero.

• 25 · A permanent contactor or similar switching device is installed in the terminal box of a permanent magnet synchronous machine • · ·: ***, each time the drive is stopped, as shown in Figures 2-5. ···. in the closed position. The switching device switches a portion of the main circuit from each phase winding to the reverse • · ···. The inverting portion of the winding is selected from the partial windings so that ♦ ♦ is applied with the same voltage as the other phase winding of that phase.

• · • ··! . 30 This occurs when the revolutions of the mutually coupled coils are the same. The speeds in the • * series are typically half the speed of the phase winding. If the 7,119,135 rotors are now rotated, the motor pole voltages will remain at zero, effectively preventing permanent magnetization from acting on the outside of the motor. When the motor is driven, the coupling device is rotated to the active position, whereupon it first activates the motor coupling to the desired triangular or star coupling according to the standard coupling described above.

Although only a three-phase motor with two partial windings is described above, the operation of the invention according to the invention may equally well be provided by a multi-phase and / or multiple sub-winding. The switching circuit only needs to be such that the partial windings of each phase can be switched so that the voltage applied at the terminals is zero.

According to the idea of the invention, it is also possible to add to the synchronous machine an additional partial winding having a conductor speed corresponding to the actual winding speed of the actual winding of the synchronous machine. This additional partial winding is connected in series with the actual winding winding, whereby their sum voltage is zero. The excess part winding may be wound from a substantially thinner conductor wire because of the small current flowing through it. Under normal 15 operating conditions, an additional partial winding may be connected open.

The invention has been described above with reference to some embodiments thereof. However, this disclosure is not to be construed as limiting the scope of the patent, but various embodiments may vary within the limits set forth in the following claims.

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Claims (13)

Synchronous machine, controllable with a frequency converter (12) connected thereto, said synchronous machine comprising a stator winding, characterized in that the stator winding comprises between two connecting poles of the synchronous machine at least one first winding 5 (Upi, Vpi, Wpi) and a second sub winding ( UP2, Vp2, WP2) to which the voltage of substantially the same magnitude is induced as the synchronous machine (10) rotates, and the synchronous machine comprises a coupling device (Κι, Κ ^, Κί), with which the first (Upi, Vp |, Wpi) and the second partial winding (UP2, VP2, WP2) can be connected in series to each other in the resting position of the coupling device, so that their voltage is opposite and that the voltage acting at connection terminals (Li, L2, L3) of the synchronous machine is substantially noil since the synchronous machine (10 ) has been disconnected from the frequency converter (12), which controls the synchronous machine. Synchronous machine according to claim 1, characterized in that the first (Upi, VphWpi) and the second part winding (UP2, VP2, WP2) form a phase winding (U, V, W) of the stator winding of the synchronous machine and that part winding can be connected in series with each other. by means of the coupling device (Ki, K2, K3) such that they induce at the connection terminals (Li, L2, L3) a voltage in the same direction, since the synchronous machine (10) is at a normal operating condition. Synchronous machine according to Claim 1, characterized in that the first * ·· * · • · ... 20 (Upi, Vpi, Wpi) and the second part winding (UP2, VP2, WP2) are connected in parallel. in the normal operation state of the synchronous machine and that the second partial winding can be connected in series to the first partial winding (Upi, Vpi, Wpi), since the synchronous machine has been switched off from the frequency converter. • · • · · ♦ Synchronous machine according to any one of claims 1 - 3, characterized in that the stator winding is triangulated. 5. Synchronous machine according to any one of claims 1 - 3, characterized in that • · • · · ....: the stator winding is coupled to the stem. * φ φ φ • V Synchronous machine according to any one of claims 1-5, characterized in that the first • φ Φ * ...: (Upi, Vpi, Wpi) and the second partial winding (UP2, VP2, WP2) have been formed by several parallel sub-circuits. . 11 119135 Synchronous machine according to any one of claims 1 to 5, characterized in that the first (Upi.Vpi.Wpi) and the second partial winding (UP2, VP2, WP2) have been formed by several series-connected sub-circuits. Synchronous machine according to Claim 1, characterized in that the coupling device 5 comprises first couplers with which the partial windings can be coupled to each other and second couplers with which the partial windings can be disconnected from wires supplying the synchronous machine. Synchronous machine according to any one of claims 1 to 8, characterized in that the ends of the sub windings are fast to the socket of the machine and that couplings between 10 sub windings can be formed with a coupler adapted in the socket. Synchronous machine according to any of claims 1-8, characterized in that the coupling device is remote controlled and is timed according to the control of the frequency converter. Synchronous machine according to any one of claims 1 - 10, characterized in that auxiliary contact of the separator at the frequency converter input has been coupled to the control of the switching device. .. Synchronous machine according to any of claims 1 - 8, characterized in that · • · * *. the coupling device is locally controlled so that the desired couplings can be carried out with the • * local control. • · · • · · · ... * 20 Synchronous machine according to claim 12, characterized in that the operation of the coupling device is direct and mechanical. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·· · · · · · · · ·