JPS6166592A - Operating method of ac variable speed shifter - Google Patents

Abstract

PURPOSE:To enable to safely and efficiently operate a boiler by inching a motor by utilizing a bypass circuit when an AC variable speed shifter falls in trouble. CONSTITUTION:When a boiler is operated by switching to a direct drive type with a bypass circuit due to a trouble, an airflow controller such as a damper is forcibly closed, an induction motor M is inched by a breaker CB2 until the damper is opened to the opening capable of flowing at the optimum flow rate, and when the damper is opened to the opening capable of flowing at the optimum flow rate for the boiler, the motor M is operated by a continuous commercial power source. Thus, even if the boiler is switched to the commercial power operation by the bypass circuit when a trouble occurs, excess air is not fed to the boiler, but the boiler can be maintained in the optimum air flow range.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] [Technical Background of the Invention and its Problems] Conventionally, drive systems for wind equipment such as boiler equipment fans and blowers have generally been driven by induction motors. Therefore, even if only a small amount of airflow was required due to the operating pattern, the induction motor was operated at the rated speed and output, and was adjusted by the opening of the damper or vane. In other words, the specific induction motor speed and output are suitable for the air volume, and the opening of the damper or vane, etc. is adjusted to accommodate the fact that the induction motor can only be operated at one foot speed. However, by fully opening the damper or vane and variably controlling the speed of the induction motor when only this small amount of air volume was required,
If the speed can be adjusted to match this air volume, energy savings can be achieved. This is a fan or processor.
For wind equipment such as, let wind tQ, pressure H1 rotation aN, and power consumption P be PocN' (“:PocQ-14, QocN, Ho
cN"), the rotational speed of the induction motor is changed according to the required air volume. (-Thus, the conventional method of constant speed operation where the scenery is controlled by damper or vane opening etc. Compared to this, it is extremely severe during low load operation patterns (:
It is a friend that can be expected to greatly reduce power consumption.

There are two ways to control the rotation speed: mechanical methods that use fluid couplings, eddy current couplings, torque converters, etc. at the joint between a constant-speed rotating electric motor and wind equipment, and electrical methods that directly control the electric motor. Mechanical methods have many drawbacks, such as being extremely inefficient and sluggish in low-speed ranges and requiring a large amount of maintenance and inspection costs, and electrical methods are generally used to control the rotational speed. The electrical rotation speed control method is a method in which a commercial AC power source is converted to an arbitrary AC frequency using a converter to directly drive an induction motor or an AC motor.

On the other hand, if a plant is made up of a wide variety of auxiliary equipment, even if one of these auxiliary equipment stops, there is a possibility that the plant will be forced to shut down. be. Therefore, in various plants, the auxiliary equipment system is configured with three units with a capacity of 50 inches, so that even if one unit stops, the other two units can continue operating with a capacity of 100 inches.

In other words, the idea is to have two Fi units in regular use during normal operation and one as a backup. However, when controlling the rotational speed using an AC variable speed device, the conversion device is usually constructed of semiconductor elements even though it is a power circuit. For this reason, it is common practice to provide a power supply bypass circuit in case the converter fails.

Referring to FIG. 1, an AC variable speed device for controlling the rotational speed of an electric motor will be explained. In the figure, CBI and CB are circuit breakers, CON is a converter, and DS is a switch.

M is an induction motor, and BO2 is a commercial AC power source.

In order to perform rotation speed control operation, a commercial AC power supply BU is required.
Obtain power from S, turn on the breaker CBl, and convert the converter C.
Supply power to ON. In the converter CON, AC power is once converted to DC using a rectifier, and then an arbitrary frequency power is generated again using an inverse converter.

When the switch D8 is closed, the arbitrary frequency 11. generated by the converter CON is generated. A power source is supplied to the induction motor M, and the induction motor M is operated at a corresponding rotation speed. By arbitrarily changing the alternating current frequency using the converter CON according to the size of the load, that is, the required air volume, the next rotation speed commensurate with the required air volume can be obtained without adding pressure loss due to dampers, etc. Needless to say, this leads to energy savings.

In this case, the landscape adjustment mechanism such as the damper is fully open (pressure loss is 1 zero'). On the other hand, if the converter CON is out of order (- means that if the circuit breaker CBl and the switch DB are opened and the circuit breaker CB is closed, in the worst case, single rotation speed control operation will be impossible. It is possible to operate at a constant speed by using a damper.

However, when operating the boiler auxiliary equipment such as fans and blowers using an AC variable speed device to control the rotation speed, there was a problem with the converter, and a direct drive method using a bypass circuit (operating with a power source) was adopted. When switching to fc and trying to operate, the damper device for controlling the air volume is forced to enter "close" control at the same time as switching to the bypass circuit, but the time to move in the "close" direction is slow due to operation by hydraulic pressure, etc. This caused a problem in that excess air was sent to the boiler, putting the inside of the boiler at risk. In other words, an excess amount of air that is more than the appropriate amount of air enters the boiler while it is in operation, resulting in incomplete combustion or, in the worst case, a misfire.

[Purpose of the Invention] In view of the above-mentioned problems, the present invention provides an AC variable speed device that enables safe and efficient operation of the boiler while maintaining the normal twisted state of the boiler using a simple method. The purpose is to provide a driving method for

[Summary of the Invention] With this in mind, in the present invention, when operating a boiler auxiliary equipment such as a fan or blower using an AC variable speed device to control the rotation speed, the AC variable speed device side I Nidrable is detected. When switching to the direct drive method (commercial power supply operation) using a bypass circuit, the landscape control devices such as dampers are forced to close once, and these dampers are guided until they reach the opening that allows the optimum air volume to flow. The electric motor is operated in an inching manner, and when the damper etc. reach an opening that allows the boiler to flow optimally, the induction motor is switched to commercial power operation.

[Embodiment of the Invention] W, 1 ff1j -i One practical example of the present invention will be described using three figures. FIG. 1 shows an AC variable speed device for an induction four-way motor with a bypass circuit. The symbols in the figure are as described above, and in order to operate the induction motor M under rotational speed control, power is obtained from the commercial AC power supply BU8, and the breaker CBI is turned on to supply power to the converter CON. Conversion device CO
In N, AC power is once converted to DC by a rectifier, and then an arbitrary AC frequency power is created again by an inverse converter. When the switch D8 is closed, the arbitrary AC frequency power generated by the converter CON is supplied to the induction motor M, and the induction motor M is operated at a corresponding rotation speed.

When performing this rotation speed control operation (: If there is a problem with the converter CON and switching to the direct drive method using the bypass circuit, that is, commercial power supply operation (- indicates switch D8
This can be done by closing breaker CB2 at the same time as opening 1≦-.Normally, to prevent such troubles, the damper device for air volume control etc. is forced to open/close at the same time as switch Da and breaker CBa are opened/closed. Figure 2 shows the phenomenon of trouble when operating at a certain arbitrary rotation speed.In other words, if a trouble occurs after 1 hour, the switch 1 open' of Da and 'close' of breaker CBS
During the time 1' until the time Tl, the induction motor M enters a powerless state, and both the motor rotational speed and the scenery decrease compared to when the motor was operated at an arbitrary rotational speed. The manner in which this reduction occurs is determined by the inertia of the motor and fan auxiliary equipment. However, when the breaker CBB is closed at 1 hour T1, the induction motor M is switched off from the commercial power supply (
The rotation speed continues to rise all at once until it reaches the rated rotation speed determined by 2, and becomes constant over a certain period of time. On the other hand, since the induction motor M, which also drives the air volume, starts up rapidly, the 7A fan, etc., suddenly increases its rated output air volume by the torque generated by the induction motor M. At this time, air volume control devices such as dampers begin closing operation to send the optimal air volume as soon as the trouble occurs, but because they are hydraulically operated, this operation is extremely slow.

In other words, the situation has not been reached to the point where the control is controlled to an optimum environment that maintains the normal combustion state of the boiler. The time it takes for an air volume control device such as a damper to reach the position where it can control this optimal air volume is about 5 to 15 seconds for a 7QQKW class blower, and 20 to 20 seconds for a 5QQQKW class blower.
It takes about 30 seconds. Therefore, during this period, excess air is continuously fed into the boiler as shown in FIG. As a result, the boiler could cause incomplete combustion, and in the worst case scenario, it could lead to a major accident such as a misfire.

Therefore, in the present invention, if there is a problem and the operation is switched to the direct drive method (commercial power supply operation) using the above-mentioned bypass circuit, the air volume control equipment such as a damper is forced (
: In addition to the 'close' operation, the induction motor M is operated in an inching manner by the circuit breaker CB2 until the damper etc. reach the opening degree that allows the damper etc. to flow optimally as shown in Fig. 3, and the damper etc. are operated optimally for the boiler. When the opening reaches a point where the air volume is flowing, the induction motor M is operated as a continuous commercial power supply.

As explained above, according to the present invention, even if the boiler is switched to commercial operation using the bypass circuit when trouble occurs, it is possible to maintain the optimum air flow rate for the boiler without feeding excess air into the boiler.

Incidentally, the driving method of the present invention may be carried out manually, or
This may be done automatically while keeping in mind the optimum air volume range for the boiler.

[Effects of the Invention] As explained above, 1. According to the present invention, even if trouble occurs during operation in the AC variable speed device, it is a % simple method (2. The optimum air volume can be continued for the boiler, and normal combustion can be achieved. This has the effect of allowing the boiler to operate safely and efficiently while maintaining its condition.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram showing an AC variable speed device with a bypass circuit applied to the present invention, and Fig. 2 is a wiring diagram showing an AC variable speed device with a bypass circuit applied to the present invention.
Figure 1 is a graph showing the phenomenon when operating using the AC variable speed device (conventional), and Figure 3 is a graph showing the air volume, damper opening degree, and machine rotation speed when using the operating method according to the present invention. It is. BU8...Commercial AC power rACBI, CB2...Shiya disconnector Da...Switch switch CON...Converter M...Induction motor agent Patent attorney Nori Chika Kensuke (and 1 other person) No. 2
Figure 1a 71 /2 13 iu□Shunjun

Claims (1)

[Claims] A method for operating an AC variable speed device for an electric motor having a bypass circuit that can be operated using a commercial power source, the method comprising performing inching operation of the motor using the bypass circuit when a trouble occurs in the AC variable speed device.