JPS5851122B2 - Drive machine control method and device - Google Patents

Description

Detailed Description of the Invention The present invention provides an induction motor and a second prime mover other than the induction motor (
The present invention relates to a method for controlling a drive machine that combines a drive machine (for example, a turbine, an engine, etc.) and an apparatus therefor.

In the following specification and drawings, the term "electric motor" refers to an "induction motor."

Rotating equipment such as compressors and pumps has traditionally been driven by electric motors, but if there is surplus steam or fuel in factories, etc., it is possible to use this steam or fuel for energy saving purposes. It is desirable to directly connect a turbine or engine to this electric motor-driven rotating machine system to effectively utilize the surplus energy.

Furthermore, even if these energies are not necessarily surplus, if the energy cost is lower than that of electrification, it is desirable to utilize this cheap energy.

However, in these cases, it is required to use surplus energy or low-cost energy with priority over electric power for various load conditions.

SUMMARY OF THE INVENTION In response to the above-mentioned conventional demands, an object of the present invention is to provide a drive machine control method and device that can use spare or low-cost energy with priority over electric power in response to load fluctuations. That is.

The present invention provides a method for driving a driving machine that combines an induction motor and a second prime mover other than the induction motor, which includes a load detection mechanism that detects load torque, and which normally receives priority based on a signal from the load detection mechanism. to cause the second prime mover to bear torque, and when the load torque becomes small and becomes equal to or less than the motor no-load torque of the induction motor, the torque of the second prime mover is increased so that the output rotation speed is approximately within a predetermined range. In the drive machine control method and the drive machine control device in which an induction motor and a second prime mover other than the induction motor are combined, the load torque is lower than the induction motor unloaded torque. The present invention is a control device for a drive machine, characterized in that it is provided with a load detection mechanism that detects this when the load detection mechanism is detected, and a torque control mechanism for a second prime mover that is controlled by a signal from the load detection mechanism.

The present invention will be described with reference to the drawings in accordance with an embodiment. In FIG. 1, a compressor 1 is driven by an electric motor 3 via a gear speed increasing device 2.

A steam turbine 4 is further connected to this drive system as a second prime mover.

Compressor 1, which is a driven machine, rotates at a constant speed (constant speed rotation in the usual expression, including cases where there is slip etc.)
An example of the torque balance when this is required is shown in Fig. 2.

That is, at the rated operating state +-0 point, the load torque is balanced with the total torque of the electric motor 3 and the steam turbine 4, and constant speed rotation is performed at 98% rotation speed with 2% slip.

Of the total torque, the torque equivalent to the length of ■-◎ is applied to electric motor 3.
The steam turbine 4
is bearing the burden.

If a governor or the like is used to control the rotation speed to 98%, the load decreases and becomes a partial load.For example, the operating point becomes point [F], and the load on the steam turbine 4 decreases, but the load on the electric motor 3 decreases. The load on the motor 3 will not be reduced, and the load on the motor 3 will be reduced only when the load decreases further and becomes below the operating point. Alternatively, there is a drawback that low-cost energy is not sufficiently utilized, and when the load force reaches a value between 0 and 0 on the Maasahi D- ■ line, the steam turbine 4 becomes a load on the electric motor 3. .

If the rotation speed is not suppressed with a governor etc., if the load decreases, the operating point (Q-
Driven at points.

In this case, the steam turbine torque decreases slightly, but the decrease in load is mostly due to a decrease in the electric motor load, which reduces slip and increases the rotational speed.

If the load further decreases, the operating point +1 is reached, at which time the load on the motor 3 becomes zero.

That is, from (2) to (F), the torque of the electric motor 3 decreases first as the load decreases, and the steam turbine torque can be used preferentially, so that the purpose of reducing power costs can be achieved.

However, if the load falls further than this, if the operation is continued, the rotational speed will drop above the operating point and the rotational speed will exceed the synchronous rotational speed of the electric motor 3.

In this case, the electric motor 3 becomes a generator and returns electricity to the power source, but this may not be desirable depending on the conditions of the power source.

Further, operation at a rotation speed exceeding 100% may cause functional problems due to system vibration, and various other problems may occur.

In order to eliminate this drawback, after reaching the switching point [F], it is required to switch the control and lower the [F]-G line without increasing the rotation speed.

For this reason, in the embodiment of the present invention, the value of the load torque decreases and the motor unburdened torque (torque when the torque borne by the electric motor becomes zero and is borne only by the second prime mover).

In Fig. 2, it is detected that the torque is below the value of point [F] (in this example, the rotation speed is controlled to 100%, so this torque corresponds to the torque at point 0). In order to do this, a load detection mechanism such as a tachometer that detects the number of revolutions of the electric motor 3 or the like or an ammeter that detects the current value of the electric motor 3 is provided, and this is used for detection.

A signal from the load detection mechanism operates the torque control mechanism of the second prime mover to lower the rotational speed along the line ■→■ in FIG. 2 so that the rotational speed does not increase.

The torque control mechanism for control on the @-〇 line is equivalent to the throttle mechanism of the steam valve when the second prime mover is a steam turbine, and the throttle mechanism of the steam valve in the case of a gas turbine, gas engine, or liquid fuel engine. The mouth aperture mechanism corresponds to this.

In the above control, when the operation is below the switching point [F], the electric motor 30
In the case where the rotation speed does not exceed 100%,
Depending on the vibration conditions and the allowable amount of power on the power supply side,
There are cases where it is acceptable for the rotation speed to exceed 100% to some extent.

At this time, if the rotation speed is to be kept within the permissible limit, for example, within the rotation speed corresponding to point Q in Figure 2, the torque corresponding to the switching point Switch to the control of the two-motor torque control mechanism and descend along the ■-■ line.

In actual driving, for example, the number of revolutions is exactly 10.
It is difficult to accurately detect the switching point [F] point corresponding to 0%, and operating points below the switching point 0 are also linear motion -◎
Although it does not move along the top of the motor accurately, the switching torque corresponding to the switching point ■ or G or ■ is detected as the motor no-load torque within the allowable limit considering the width of the error, and the second prime mover The torque of the electric motor 3 can be controlled to always reduce the share of the electric motor 3 regardless of the magnitude of the load.

The components of the drive machine and their arrangement may be different from those shown in Figure 1, such as a reduction gear instead of a gear speed increaser, a power transmission mechanism other than gears such as a belt, chain, or hydraulics, or a combination of these. In some cases, the electric motor is directly connected without using a second prime mover, and in other cases, the arrangement of the second prime mover and the electric motor is reversed. In addition to a steam turbine, a gas turbine, a gas engine, a liquid fuel engine, etc. are used as the second prime mover.

The same effect can be obtained even if a rotary machine such as a blower or a pump is used in addition to the compressor as the driven machine.

According to the present invention, it is possible to perform control to minimize the consumption of electric motor power by giving priority to the power of the second prime mover in any case when the load fluctuates, and effectively utilizing surplus or low-cost energy. In addition, it is possible to provide a drive machine control method and device that can reduce power costs, and has an extremely effective energy saving effect in practice.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a layout diagram showing the configuration of a driving machine, and FIG. 2 is a graph showing torque balance. 1...Compressor, 2...Gear speed increaser,
3...Electric motor, 4...Steam turbine.

Claims (1)

[Scope of Claims] 1. A method for driving a drive machine that combines an induction motor and a second prime mover other than the induction motor, which includes a load detection mechanism that detects load torque, and uses a signal from the load detection mechanism to: Normally, torque is given priority to the second prime mover, and when the load torque becomes small and becomes equal to or less than the motor no-load torque of the induction motor, the second prime mover is set so that the output rotation speed is approximately within a predetermined range. A method for controlling a drive machine, characterized in that the torque of a prime mover is controlled. 2. A control device for a drive machine that combines an induction motor and a second prime mover other than the induction motor, which is equipped with a load detection mechanism that detects when the load torque falls below the induction motor no-load torque; A control device for a drive machine, comprising a torque control mechanism for a second prime mover that is controlled by a signal from a detection mechanism.