JPH04255480A - Method for starting belt conveyor - Google Patents

Abstract

PURPOSE:To smoothly start a belt conveyer where a winding type induction motor is used regardless of load. CONSTITUTION:A belt conveyer is started through a controller (sequencer) 4 while advancing the secondary resistor 3 of an induction motor 1 in order from no-load. And it is detected that the belt conveyer has actually begun to start, and load torque is determined from the value (resistance value selected by an electromagnetic contactor 4) of the resistance notch at that time, and further calculates the value of this load torque is calculated, the start notch pattern by the use of which the specified accelerating torque can be gotten from the load torque is selected referring to the memory table stored beforehand in a memory, and based on this start notch, the belt conveyer is started.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a belt conveyor driven by a wound induction motor, and particularly to an improvement thereof.

0002

2. Description of the Related Art In a wound induction motor, a resistor is usually connected to the secondary side of the motor through a slip ring in order to obtain a large starting torque and at the same time limit the starting current. In this case, the resistors inserted on the secondary side are gradually decreased from the maximum value (hereinafter also referred to as resistance notch advancement), and eventually short-circuited. That is, conventionally, it is common to advance through predetermined resistance notches one by one using a current limiting relay, a timer, or the like.

FIG. 3 is a schematic diagram showing an example using a current limiting relay. In the figure, 1 is a wound induction motor, 3 is a 2
Next (starting) resistor, L is current limiting relay, C is its contact,
MC1 to MCn each indicate a magnetic contactor. That is, in this example, while closing the electromagnetic contactors MCn to MC1 as appropriate, the resistances are successively removed (reduced). Here, this notch advancement is carried out by notifying a control device (not shown) via contact C of the current-limiting relay, but there are other methods such as using only a timer and using a current-limiting relay and a timer. There are ways to use them together.

0004

[Problems to be Solved by the Invention] However, with this method, mainly due to cost issues, it is difficult to obtain a large number of resistance notches, that is, a large number of notch patterns, and the acceleration torque is reduced due to the size of the actual load on the belt conveyor. There are problems such as a smooth start-up due to changes in the belt conveyor, which may have a negative impact on the life of the belt conveyor, or wasteful system design when starting multiple belt conveyors. . Therefore, an object of the present invention is to provide a starting method for smoothly starting a belt conveyor using a wound induction motor.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides at least a speed detector for the motor of a belt conveyor driven by a wound induction motor. While sequentially advancing the resistance notches inserted on the secondary side, the speed detector detects that the belt conveyor has actually started moving,
After determining the actual load torque value from the resistance notch value at that time, an acceleration notch pattern is determined by referring to a pre-stored table from this load torque value and a predetermined acceleration torque value, and the acceleration rate of the belt conveyor is determined. The present invention is characterized in that the acceleration notches are sequentially advanced based on the determined pattern when the value becomes equal to or less than a predetermined value.

[0006]

[Operation] Detects the actual load on the belt conveyor while advancing the resistance notches one after another and determines the acceleration notch pattern.
After checking the acceleration rate, the resistance notches are sequentially advanced in a predetermined pattern to enable smooth starting that is independent of the load.

[0007]

Embodiment FIG. 1 is an explanatory diagram for explaining an embodiment of the present invention. In the same figure, 1 is a wound induction motor (M
), 2 is a speed detector (SD), 3 is a secondary resistor, 4 is a starting controller, 5 is a setting device, and MC1 to MCn are electromagnetic contactors. Note that the reference numeral S1 of the starting controller 4
~S4 indicate processing steps performed by the controller, respectively. Further, a speed detector 2 is provided to confirm the startup of the belt conveyor and to check the acceleration rate (acceleration), and a setting device 5 is comprised of a digital switch or the like and is provided to appropriately set a certain acceleration torque Ta. ing.

That is, a speed detector 2 is attached to a wound induction motor 1 for starting a belt conveyor, and a secondary resistor 3 has resistance values of 2n (n: number of electromagnetic contactors) by electromagnetic contactors MCn to MC1. (If the number of electromagnetic contactors is 8, 28=256 choices can be made). Note that this selection method has been conventionally known as a matrix method.

[0009] Here, the operation steps S1 to S4 of the starting controller will be explained. First, in step S1, the starting controller 4 detects the point in time when the belt conveyor actually starts starting while advancing the notches of the secondary resistor sequentially from no-load, and calculates the load torque value from the value of the resistance notch at that time. Understand the TL. Next, from the load torque value TL obtained above, a starting notch pattern that provides a predetermined acceleration torque value Ta is selected (see step S2).
. At this time, the value of Ta is determined by the setting device 5 as described above.
Can be set arbitrarily. In addition, in order to obtain the starting notch pattern from the load torque value TL and the acceleration torque value Ta, for example, a memory table T is created and prepared in advance, and the starting notch pattern can be obtained simply by referring to this memory table T. Let's keep it like this. Note that it is conceivable to prepare, for example, several dozen types of starting notch patterns here.

Next, the belt conveyor is started based on the selected starting notch pattern. Then, check the acceleration rate (velocity differential value dv/dt) and
When /dt≦a, the notch is switched to the next notch, and this is sequentially repeated until activation is completed (see steps S3 and S4). Note that a is a set value, and a constant value close to 0 (≈0) is selected. Further, completion of startup shall be appropriately determined by the startup controller 4 shown in FIG. 1.

FIG. 2 shows a speed diagram for explaining the operation of FIG.
It is a torque characteristic diagram. In addition, in the same figure, TL0 is no-load torque, TL is load torque, Ta is acceleration torque, Ns is no-load notch, Ns to Nn are starting notches, Ni is acceleration notch, and Nf is final notch (motor secondary short circuit). are shown respectively. That is, while advancing the notches of the secondary resistor sequentially from no-load (maximum notch Ns) (Ns to Nn)
, detect the point at which the belt conveyor actually starts to start,
The load torque value is determined from the resistance notch value at that time. For example, if the notch curve at that time corresponds to Nn, the actual load torque TL can be calculated by multiplying the torque value at speed 0 of that curve (Nn) by a certain ratio.
(corresponding to the area of the shaded area in the figure) is calculated. When the actual load torque TL is determined, the memory table T is referred to from this and the acceleration torque value Ta set by the setting device 5, and a starting notch pattern Ni to N as shown in FIG.
Find f. Thereafter, when the acceleration rate becomes less than a certain value a, the notch pattern is switched to the next notch pattern (Ni), and the notch patterns are sequentially advanced from Nh to Nf in the same manner. Note that the notch advance at this time is performed by a current limiting relay or a timer, as in the conventional case.

In this way, since the actual load of the wound induction motor is detected and the optimum resistance notch pattern is determined for startup, the belt conveyor can be started smoothly no matter what the load is. It becomes possible to do so.

[0013]

[Effects of the Invention] According to the present invention, the acceleration notch pattern is determined by actually detecting the load on the belt conveyor, and after checking the acceleration rate, the notch is advanced according to that pattern, regardless of the load. This makes it possible to start the engine smoothly with constant acceleration torque. Further, here, since it is not necessary to use a load detection device, a speed feedback calculation device, etc. by simply adding a speed detector, there is also an advantage that the belt conveyor can be started easily and at low cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining an embodiment of the present invention.

FIG. 2 is a speed-torque characteristic diagram for explaining the operation of FIG. 1;

FIG. 3 is a schematic diagram for explaining a conventional example.

[Explanation of symbols]

1 Wound induction motor (M) 2 Speed detector (SD) 3 Secondary resistor 4 Startup controller 5 Setting device T Memory table L Current limiting relay TL Load torque Ta Acceleration torque MC1 Magnetic contactor MC2 Magnetic contactor MC3 Magnetic contactor MCn Magnetic contactor

Claims (1)

[Claims] 1. At least a speed detector is provided for the motor of a belt conveyor driven by a wound induction motor, and the speed is detected while sequentially advancing resistance notches inserted on the secondary side of the motor. The controller detects that the belt conveyor has actually started moving, and the actual load torque value is determined from the value of the resistance notch at that time.Then, the actual load torque value is stored in advance from this load torque value and a predetermined acceleration torque value. A method for starting a belt conveyor, characterized in that an acceleration notch pattern is determined by referring to a table, and when the acceleration rate of the belt conveyor becomes equal to or less than a predetermined value, the acceleration notches are sequentially advanced based on the determined pattern. .