JPH0786068B2 - AC elevator control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an elevator control device using an AC electric motor, and particularly to an AC elevator control device using an inverter control.

[Conventional technology]

As is well known, an inverter control is being adopted in an elevator using an induction motor, and in particular, so-called vector control is adopted in order to smoothly perform speed control of the elevator.

Normally, the elevator requires the maximum torque from start-up to acceleration, and is 200 to 250% of the rated electric motor. If the inverter device is only in normal operation, it can withstand this 250% current.

By the way, as one of safety devices, the elevator is provided with an emergency stop device that holds the guide rail and stops the fall of the car when it is in a free fall state. It is necessary to test and confirm this emergency stop device at the time of elevator construction and at regular intervals. At this time, the electric motor requires up to approximately 300% of the rated torque. Since a large current is required to generate this torque, the inverter capacity also becomes large and expensive.

As a method of remedying this drawback, as disclosed in Japanese Patent Laid-Open No. 62-56275, the elevator is operated by using the first exciting current command during normal operation, which is the same as during an emergency stop test. There is disclosed a method of performing vector control using a second exciting current command larger than the first exciting current command when such a large tokule is required.

[Problems to be Solved by the Invention]

In the above-mentioned prior art, in so-called slip frequency type vector control in which the slip frequency of the electric motor is detected and vector control is performed, an increase in the excitation current command does not contribute to an increase in torque.

Generally, the torque τ of the electric motor is expressed as a function of the primary current I ₁ and the slip frequency ω _s .

τ = F (I ₁ , ω _s ) (1) Accordingly, even if the excitation current command is increased, the primary current is suppressed by the current limiter and the current does not increase, so the torque cannot be increased.

An object of the present invention is to provide a control device that can effectively increase the electric motor torque within a limited primary current range.

[Means for Solving the Problems]

The present invention provides an operating means for switching to a smaller slip frequency than during normal operation during a specific operation in which a sufficiently large load is applied to an electric motor as compared with during normal operation as an elevator, for example, during an emergency stop test. And is provided.

[Action]

During a specific operation such as an emergency stop test, the elevator drive motor is operated, for example, by operating an emergency stop device to apply a sufficiently large load as compared with the normal operation, thereby suppressing the speed increase. In this way, when the speed is suppressed, the motor current maintains its maximum value, and under this limited current, the torque can be easily increased by operating the switching operation means that switches the slip frequency to a smaller value. Can be made.

〔Example〕

FIG. 1 shows an embodiment of the present invention. Hoisting machine 3 is a car 5
The counterweight 4 is arranged in a rope shape via a rope, and the car 5 is provided with an emergency stop device 6. During the emergency stop operation, the device 6 holds the rail 7 and stops the elevator from descending. The electric motor 1 is coupled to the hoisting machine 3, and the encoder 2 is directly connected to the shaft of the electric motor 1. A well-known inverter device 8 driven by the electric motor 1 is inserted between the motor device 1 and the power source 9. This inverter may be a current type or a voltage type.

The speed command ω _r * is output from the speed command generator 10, compared with the speed signal ω _r of the encoder 2, and a predetermined torque command τ * is output via the speed adjuster ASR and the torque limiter TL. In normal operation, the switch SW ₁ operates in the direction shown in the figure, and the slip frequency ω
_The slip frequency ω _s is obtained via the calculator G ₁ that calculates _s . The sum of the slip frequency ω _s and the speed signal ω _r is the inverter frequency ω ₁ . On the other hand, from the torque command τ *
The product of the slip frequency ω _s and the secondary time constant T ₂ (hereinafter abbreviated as torque component) ω _s * T ₂ is obtained via G ₃ , and the excitation current command is generated.
From I _m Is calculated and the primary current command I ₁ is output via the current limiter IL. The output of G ₃ calculates tan ⁻¹ (ω _s T ₂ ) and outputs the phase θ. The above I ₁ , ω ₁ , and θ are input to the PWM circuit to determine the pulse train of the switching element of the inverter 8, and the electric motor 1 is controlled according to the torque command.

As described above, the emergency stop test requires a larger torque than that required for normal operation. Since the inverter capacity is designed so that it can be operated normally, the current limiter cannot be made variable for control purposes. usually,
In the emergency stop test, when the safety device is operated, the electric power is supplied to the electric motor, and when it is confirmed that the rope has started to slide, the emergency stop device is judged to have passed and the operation is terminated. Therefore, the speed ω _r does not follow the speed command ω _r * at this time because a large torque is required although the speed is sufficiently lower than the rotation speed of the electric motor during normal operation. Therefore, the speed regulator ASR becomes saturated and its output reaches the torque limiter TL. Further, since the value of the current limiter IL is set in correspondence with the torque limiter operation, the current limiter also operates. That is, during the emergency stop test, the control is saturated and torque command τ * = torque limiter value (2) current command I ₁ = current limiter value (3).

By the way, in general, the steady torque τ of the electric motor can be expressed as a relation between the magnitude I _{1 of} the primary current and the slip frequency ω _s , and is expressed by the following equation.

Here, T ₂ is the secondary time constant of the motor.

As described above, during the emergency stop test, the output current I _{1 of the} inverter saturates and becomes a constant value at its maximum value. Therefore, I ₁ = constant in the equation (4), and the torque τ and (ω
The relationship of _s T ₂ ) is shown in FIG.

When the slip frequency calculator G ₁ during normal operation is used, the torque during the emergency stop test becomes A in Fig. 2, but as can be seen from the figure, when ω _s T ₂ is decreased, the torque increases and ω _s T ₂
It becomes the maximum when = 1. The secondary time constant T ₂ is a value peculiar to the motor, and the slip frequency ω _s can be controlled.
The calculation gain of the slip frequency may be reduced by using a specific switch only during the emergency stop test. That is, in FIG. 1, during the emergency stop test, the switch SW ₁ is operated in the opposite direction to the torque command τ * prior to the test.
Slip frequency ω through the second slip frequency calculator G ₂ (the gain of G ₂ is smaller than G ₁ )
_s is calculated. By doing so, the torque becomes point B in FIG. 2, and although the current value does not change, the torque is larger than A.

In the present embodiment, with respect to the electric motor, during a specific operation in which a sufficiently large load is applied as compared with the normal operation as an elevator, the relationship between the slip frequency and the primary current with respect to the torque command is smaller than that during the normal operation. And change the torque to increase the torque.

Another embodiment will be described with reference to FIG. In this other embodiment, the torque command is reduced and the slip frequency is reduced accordingly. On the other hand, by maintaining the primary current at the value during normal operation, the relationship between the slip frequency and the primary current for the torque command is switched to increase the torque. That is, during the emergency stop test, the switch SW ₁ operates toward the dotted line and is connected to the second torque limiter TL ₂ . In order to reduce the slip frequency ω _s , not the gain G ₁ , but the torque limiter from the first torque limiter TL ₁ to TL ₂ (this limiter value is
It has been set smaller than TL ₁ ). Then, as the value of this smaller summer was torque command tau * the primary current is not reduced, the switch SW _1, the calculator G3B are connected. The gain of this calculator G3B is the gain G during normal operation.
For 3A, As a result, the torque component (ω _s T ₂ ) is not affected even if the tricrimitter becomes smaller.

〔The invention's effect〕

According to the present invention, the torque can be increased without increasing the inverter capacity for the specific operation such as the emergency stop test.

[Brief description of drawings]

FIG. 1 is a control block diagram of an embodiment of the present invention, FIG. 2 is a torque characteristic diagram at a constant current, and FIG. 3 is a control block diagram of another embodiment of the present invention. SW ₁ …… Switch for emergency stop test, G ₁ , G ₂ …… First and second calculators for determining slip frequency, TL ₁ , TL ₂ …… First and second torque limiters.

Claims (4)

[Claims] 1. An elevator serving a plurality of floors,
An induction motor that drives an elevator, and a control device for an AC elevator that controls the induction motor and that includes an inverter device that employs a slip frequency vector control, with respect to the electric motor, as compared with normal operation as an elevator. A control device for an AC elevator equipped with an operating means that switches the slip frequency to a lower value during a specific operation in which a sufficiently large load is applied as compared to during a normal operation. 2. The control device for an AC elevator according to claim 1, wherein the switching operation means includes means for switching a calculation gain of a slip frequency obtained from a torque command to a small value. 3. The switching operation means according to claim 1, wherein a first torque limiter set during a normal operation, a second torque limiter set to be smaller than an output value of the first torque limiter, and a specific operation, A control device for an AC elevator, comprising: means for switching from the first torque limiter to the second torque limiter; and means for increasing a calculation gain of a primary current command obtained according to the output of the second torque limiter. 4. A control device for an AC elevator according to claim 1, wherein said heavy load applying means includes means for activating an emergency stop device of said elevator.