JPH0810963B2 - Drive device by linear induction motor - Google Patents

Description

Detailed Description of the Invention

<Field of Industrial Application> The present invention relates to a drive device using a linear induction motor. <Prior Art> A linear induction motor has a large exciting current, a low power factor, and a low efficiency as compared with a general rotary induction motor, and its primary and secondary operations are relatively separated. Therefore, it is often used intermittently, and very rarely used as a drive device for continuous operation. However, the linear induction motor does not require a power transmission mechanism and can obtain thrust without contact, and therefore has many advantages such as low wear parts, low noise, low vibration and low dust generation. Further, it has many advantages such as being able to be mechanically incorporated into the device, and its adoption is gradually being considered as a drive device of a device that performs cyclic traveling. The cyclic traveling device is a device that continuously circulates and travels a carrier (a trolley loaded with luggage) arranged endlessly connected to a circulation type traveling path. An example of the carrier device is an automatic baggage sorting device implemented in a physical distribution center or the like. This device allows the endlessly connected conveyors to run continuously at a constant speed on a running path laid in a loop.
When the carrier arrives at a preset package sorting position, the package loaded on the carrier is automatically carried out. A linear induction motor formed by a stator distributed in a primary form on the ground along the traveling path and a reaction plate provided facing the stator on the carrier is used as a drive source of the carrier. ing.

[Problems to be Solved by the Invention]

However, in the above-described transport device, there is a large difference between the thrust required at startup and acceleration at full load and the thrust required at no load at the steady speed. In the case of a rotary induction motor, generally, it is often driven by obtaining a constant speed and high torque via a reduction gear, but in the case of driving by a linear induction motor, it is a direct drive, so it is necessary to directly generate high thrust. Therefore, the linear induction motor tends to have a large shape, and a plurality of linear induction motors are often adopted as the distributed arrangement method.
In this case, the output of the linear induction motor is reduced in the case of light load motion compared to the maximum thrust, as in the case of the rotary induction motor.However, since the linear induction motor has a large excitation current, the load Even if the output changes with increase or decrease, the current value is almost constant, and the apparent apparent power (KVA) does not change much. However, as the phase difference (power factor) between voltage and current changes, the effective power increases or decreases with the load.
Therefore, in a continuous drive system with multiple linear induction motors, the heat loss caused by a relatively large exciting current and the coil resistance of the motor does not change much even when all linear induction motors are excited even at light load. Due to the characteristics of the motor, the efficiency is low when the load is light, and it cannot be said to be an appropriate system for high-efficiency operation. The present invention was devised in view of the above circumstances, and always grasps the input of the linear induction motor, and when the load becomes lighter than a predetermined electric power value, the linear induction motors are operated one by one by disconnecting them and operating. The linear induction motor is controlled so that it is always in a state as close to the rated value as possible, and an object thereof is to provide a drive device using the linear induction motor that enables high efficiency. <Means for Solving the Problems> A drive device using a linear induction motor according to the present invention is a linear drive system in which a plurality of endlessly connected carriers are distributed and arranged in a primary form on the ground along a running path formed in a loop. In a transport device that continuously runs with an induction motor,
Converts input power of linear induction motor to signal output voltage
It is provided with a W / V converter and a control unit for connecting and disconnecting the linear induction motor based on the output signal of the W / V converter, and the control unit is for accelerating and decelerating and performing heavy load on the carrier. It is characterized in that a large number of linear induction motors are connected at the time of load and the linear induction motors other than the required number are disconnected at the time of constant speed and light load. <Operation> The W / V converter inputs the input power of the linear induction motor to the control unit as a signal output voltage. The control unit connects or disconnects the linear induction motor according to the magnitude of the signal output voltage. <Example> Hereinafter, an example according to the present invention will be described with reference to the drawings. FIG. 1 (a) is a circuit diagram of a method for detecting the total input power of a drive system, and FIG. 1 (b) is a circuit diagram of a method for detecting the input power of one linear induction motor in the drive system. . In the figure, LIM ₁ , LIM ₂ , LIM ₃ ... LIM _N are linear induction motors constituting the drive system, S is the main switch of the device, and S ₁ , S ₂ , ... S _N-1 Indicates a switch for each linear induction motor, and the W / V converter is a device that generates a predetermined signal output voltage according to the input power of the inserted circuit. The control unit C includes the electromagnetic coils of the switches S1, S2, ... Sn-1 and is configured to operate the electromagnetic coils based on the signal output voltage output from the W / V converter. ing. In the figure, V is a carrier. (1) Method of detecting total input power The relationship between the signal output voltage and the input power of the W / V converter is generally represented by a straight line 1 in FIG. Now
If the signal output at maximum load is P ₀ , driving by all LIMs is required at this point, and switches S and S ₁ , S ₂ ,.
... All S _N-1 are in the ON state. Now, P ₁ , P ₂ , ... P _N-1 on the straight line l are
_{S 1, S 2, ···· S} N-1 switch off voltage, Q _1, Q _2, ·
· · · Q _N-1 is S _1, S ₂ respectively, if ···· S _N-1 switches on voltage, load is reduced during the time of operation the maximum load,
When the output signal voltage of P ₁ is reached, S ₁ turns off and LIM ₁ is disconnected. Furthermore the load is reduced, if the output signal voltage and P ₂
Open to S _2, ie LIM ₂ . Conversely, when the load increases to Q ₂ , S ₂ turns on and LIM ₂ is excited. In this way, the number of operating LIMs is controlled by always selecting the optimum state according to the increase or decrease of the load. The reason why the on / off voltage values for each switch are different is that if the on / off values are the same, chattering occurs during switch operation, which hinders stable control. For this reason, the ON voltage of each switch is set to a value slightly higher than the OFF voltage for stable control. (2) Method for detecting the input power of one LIM The circuit configuration is shown in Fig. 1 (b). In this method, the control unit C includes a pulse oscillator, a stepping relay, and an electromagnetic coil of each switch, and among the installed LIMs, the output signal of the W / V converter connected to the LIM _N that does not open to the end. The pulse oscillator and each switch work via a stepping relay. The characteristics of the converter are represented by the straight line l in Fig. 3. If the output signal voltage value at maximum load is P ₀ , a negative pulse is generated in the pulse oscillator when the value P ₁ is P ₀ > P _1. Then, when Q ₁ such that P ₀ <Q _{1, the} same positive pulse is generated. For stepping relays, one that operates with a positive pulse and one that operates with a negative pulse are installed. One with a positive pulse performs the operation of sequentially turning on one LIM switch for each pulse, and one with a negative pulse. Performs the operation of opening one LIM switch for each pulse. When the load of the LIM group that was operating at P ₀ now decreases, naturally the shared load per LIM unit also decreases, and when the P ₁ point is reached, a negative pulse is generated and the stepping relay is switched off. It works and one LIM is disconnected. When one unit is disconnected, the load per unit of the existing LIM group increases, so the output signal voltage of the converter rises to around P ₀ . Subsequently, followed by reduction of the load, if Itare again to _point P, by the same operation, S ₂ is opened, LIM ₂ are disconnected. Here, when the load is increased, and rises to _a point Q, the pulse oscillator generates a positive pulse, the stepping relay operates one stage, was charged with S _2, and connect the LIM _2, sharing The load is reduced and operation is performed near the output signal voltage P ₀ . By repeating the above-described detection and operation, the drive device can always operate while maintaining an efficient state. Furthermore, the present invention requires not only the load fluctuation but also the total thrust of all the machines at the time of acceleration when controlling the LIM group by the VVVF inverter, but in the steady operation, in the relatively low frequency region. In many cases, the operation is continued, so it can be applied even in this case. When operating in the low frequency region, the voltage is also low, so the shared output of the LIM group is reduced, and the number of LIMs can be reduced to increase the shared output of each LIM and automatically maintain high efficiency operation. There are great advantages in terms. In the embodiment of the present invention, the switch of each LIM is an electromagnetic switch, but a contactless switch mechanism made of a semiconductor such as a thyristor or a triac is exactly the same, and in particular, the power source has an electronic mechanism such as an inverter. If
It is more effective to use a semiconductor switch in order to prevent the occurrence of switching surges and the like. <Effects of the Invention> Since the present invention is configured as described above, the input of the linear induction motor is constantly grasped, and if the load becomes lighter than a predetermined electric power value, the linear induction motors are separated one by one and operated,
The linear induction motor in operation is controlled so as to always be as close to the rated value as possible, and it is possible to provide a drive device using the linear induction motor that enables high efficiency.

[Brief description of drawings]

FIG. 1 is a block diagram of the circuit of the present invention, FIG. 2 is a drawing showing the relationship of the output signal voltage with respect to the input power of the W / V converter in the case of the method of detecting the total input power, and FIG.
5 is a diagram showing the relationship between the input power of the W / V converter and the output signal voltage in the case of the method of detecting the input voltage of the LIM of the stand.

Claims (1)

[Claims] 1. A plurality of endlessly connected carriers,
A W / V converter that converts the input power of a linear induction motor to a signal output voltage in a carrier device that continuously travels by linear induction motors distributed in a primary form on the ground along a running path formed in a loop, and this W And a control unit for connecting and disconnecting the linear induction motor based on the output signal of the / V converter, and the control unit connects a large number of linear induction motors during acceleration / deceleration and heavy load of the carrier. However, the linear induction motor drive device is characterized in that the linear induction motors other than the required number are disconnected at constant speed and light load.