JPS6363318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive control device for a press machine or the like equipped with a flywheel having a large mass.

In a mechanical device such as a crank press that has a flywheel with a large mass, the energy required by the load (machine) is not continuous, but is instantaneously required during a limited period of one cycle. Therefore, in this type of mechanical device, energy can be stored in the flywheel during the period from the generation of a load in the previous cycle until the generation of the next load, and this stored energy can be released in a limited short period (when a load occurs). Therefore, there is an advantage that a motor with a small output can be used compared to the load requirement.

However, in the past, a constant voltage was supplied to the three-phase induction motor that rotates the flywheel, so the input to the motor during no-load and light-load conditions was greater than necessary, necessitating so-called reactive power. Therefore, there was a drawback that electric energy could not always be used effectively.

The present invention has been made in view of the above, and includes:
By detecting the released load energy of the flywheel through the slippage of the electric motor (detecting the stored energy) and controlling the primary supply voltage of the motor with a thyristor device in response to this released load energy, sufficient energy is supplied to the flywheel. The purpose is to reduce the primary supply voltage of the motor to suppress the so-called no-load current when the motor is accumulated, thereby reducing the driving cost of the press machine etc. without adversely affecting its stability. It is something.

The present invention will be described below with reference to an illustrated embodiment.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which a flywheel 1 of a press machine (not shown), etc.
A slip detector 3 composed of a pulse generator is connected to the main shaft of a three-phase induction motor 2 that rotates the motor.

Further, by interposing a thyristor device 4 in the power supply circuit of the electric motor 2, the primary supply voltage of the electric motor 2 can be controlled.

Here, the gate circuit 5 of the thyristor device 4
The output of the slip detector 3 and the output of the reference setter 7 are supplied to the arithmetic unit 6 that controls the slip of the three-phase induction motor 2, that is, according to the load energy released by the flywheel 1. The primary supply voltage of the electric motor 2 can be controlled.

That is, when sufficient energy is stored in the flywheel 1, the slippage of the three-phase induction motor 2 becomes the same as the slippage under no load, and energy is released from the flywheel and the rotational speed of the flywheel decreases. Along with this, the slippage of the electric motor 2 increases. Therefore, if this slippage is detected,
Since the discharge load energy of the flywheel 1 (required load energy of a press machine, etc.) can be known, reactive power can be suppressed by controlling the primary supply voltage of the motor 2 according to the magnitude of this discharge load energy. be.

FIG. 2 is a characteristic diagram of the three-phase induction motor 2, and
By changing the primary supply voltage of the motor 2, the motor 2
The characteristics of change. Furthermore, when the energy stored in the flywheel 1 is released, the slippage increases as shown by the characteristic line in the figure. Therefore, the slip ns (output of reference setter 7) during actual no-load operation
By comparing and calculating the actual slip na, nb, nc, nd, . Since an appropriate primary voltage of ~d is supplied to the electric motor 2, a motor torque (load torque) Ta~Td corresponding to the load energy released by the flywheel 1 can be obtained.

Therefore, sufficient energy is stored in the flywheel 1 between the generation of load in the previous cycle and the generation of load in the next cycle, and after sufficient energy is stored, the supply voltage of the motor 2 is gradually lowered, so-called Suppress reactive power. Therefore, when the standby operation period is long, the power consumption of the electric motor can be more effectively reduced and the operating cost of the press machine etc. can be reduced.

In the embodiment, the slip detector is configured with a pulse generator, but it may be a so-called tachometer generator, and in short, the slip detector may have any structure as long as it can detect slip of the motor. Furthermore, slippage of the electric motor can be detected based on the rotational speed of the flywheel, and the primary supply voltage may be corrected and controlled in accordance with the standby operation time.

As explained above, according to the present invention, the primary supply voltage of the electric motor can be automatically controlled according to the load energy released by the flywheel, so that it is possible to continue supplying a constant voltage to the electric motor as in the conventional case. Compared to this, the reactive power at no-load and light-load times can be reduced, and the operating cost of the motor can be reduced. Further, when the load energy released by the flywheel is large, the voltage supplied to the electric motor becomes high and the load torque thereof becomes large, so there is no fear that the drivability of the press machine etc. will be impaired.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. FIG. 2 is a characteristic curve diagram of a three-phase induction motor when the primary supply voltage is changed. DESCRIPTION OF SYMBOLS 1...Flywheel, 5...Gate circuit, 2...Three-phase induction motor, 6...Arithmetic unit, 3...Slip detector, 7...Reference setter, 4...Thyristor device.

Claims (1)

[Claims] 1. In a press machine or the like equipped with a flywheel having a large mass, means for detecting load energy released from the flywheel through the slippage of a three-phase induction motor that rotationally drives the flywheel, and controlling the primary supply voltage of the motor. 1. A drive control device for a press machine, etc., comprising a thyristor device that increases the primary supply voltage of a three-phase induction motor as load energy emitted from a flywheel increases.