JPH0440955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply device that supplies power to a motor that is frequently driven and stopped.

[Conventional technology]

In general, many industrial sewing machines are driven by the power of a motor, but as disclosed in Japanese Patent Application Laid-open No. 59-204471, AC voltage is used based on DC voltage. There is a system that generates AC voltage and controls the voltage and frequency of this AC voltage to the optimal values for driving a motor.

Figure 3 is a block diagram showing its outline.
Signal for controlling the value of DC voltage by control circuit 1
By generating V _dc and a signal v _f that controls the frequency of the AC voltage supplied to the motor 2, a desired DC voltage V _Dc is generated from the chopper 3 and the capacitor 4, which are the DC voltage generating section. An alternating current voltage having a desired frequency is generated by an inverter 5 based on the current. At this time, by controlling changes in the signal v _dc and the signal v _f by the control circuit 1, the characteristics shown by the solid line in FIG. 4 are obtained.

When the motor 2 is stopped or decelerated, a regenerative voltage is generated in the motor rotating due to inertia. The circuit of the inverter 5 is disclosed in detail in Japanese Patent Laid-Open No. 59-204471, but since the voltage supplied from the motor side passes through to the chopper side, this regenerative voltage is absorbed. Therefore, a regenerative voltage absorption circuit 8 consisting of a transistor 6 and a resistor 7 is provided. This circuit is driven by a comparison circuit 10 which compares the reference voltage 9 and the terminal voltage of the capacitor 4. Note that 11 is a DC power supply for the chopper 3.

If the regenerative current flowing from the inverter 5 to the capacitor 4 is _d , the regenerative power W _R is expressed by the following formula.

W _R = _d ×V When _{the DC} regenerative current _d increases, the terminal voltage of the capacitor 4 increases. If the _voltage of the reference voltage 9 is set to V _DcY higher than the voltage V _Dcx shown in FIG. Consumed at 7. Then, when the terminal voltage of the capacitor 4 becomes lower than the voltage V _DcY , the transistor 6 is turned off.

[Problem that the invention seeks to solve]

However, in such conventional devices, the value of the reference voltage is constant, and the chopper 3 does not have a damping voltage absorption function, so the voltage V _DC cannot be controlled by the chopper 3 during regeneration, and the When regeneration is performed in the range a in FIG. 4, the motor 2 becomes over-excited. On the other hand, since sudden acceleration and sudden deceleration are frequently repeated during sewing operations using a sewing machine, the motor 2 has a disadvantage in that it generates heat due to regenerative current during sudden deceleration. The present invention has been made to solve these problems, and an object of the present invention is to provide a power supply device that does not generate heat in the motor during regeneration.

[Means for solving problems]

The device of the present invention includes a comparison voltage generation circuit that generates a comparison voltage by adding a certain voltage to a command voltage, and a comparison circuit that operates a regeneration voltage absorption device when the regeneration voltage becomes higher than the comparison voltage. It is.

[Effect]

The operating voltage of the regenerative voltage absorption device changes in conjunction with the command voltage.

[Practical example]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and the same or equivalent parts as in FIG. 3 are designated by the same symbols. In the figure, 20 is an adder circuit which is a comparison voltage generation circuit, 21 is a power supply that generates a constant voltage, and 22 is a differential amplifier.

In the device configured in this way, the chopper 3 generates a DC voltage corresponding to the command voltage v _dc ,
The inverter 5 converts the second voltage based on the generated DC voltage.
An AC voltage with an optimum frequency that follows the characteristics shown by the solid line in the figure is generated, and this voltage is supplied to the motor 2.
As a result, the motor 2 is started at the optimum frequency and optimum voltage.

On the other hand, the command voltage v _dc is added to the voltage of the power supply 21 in the adder circuit 20 and supplied to the comparator circuit 10 , and the output voltage of the chopper 3 is supplied to the other input terminal of the comparator circuit 10 . As shown by the dotted line in FIG. 2, the output voltage of the adder circuit 20 is
If the relationship between the control voltage v _dc and the voltage of the power supply 21 is determined so that it is always higher than the output voltage of the chopper 2 shown by the solid line, the transistor 6 will not be turned on while the motor 2 is being driven.

When the motor 2 stops or decelerates, a regenerative voltage is generated and the voltage is supplied to the comparator circuit 10 via the inverter 5. If the value is larger than the value indicated by the dotted line in FIG. Generates an output signal that turns on. Therefore, the regenerated power is consumed by the resistor 7, and the terminal voltage of the capacitor 4 does not rise above the voltage indicated by the dotted line in FIG.
The motor 2 is not placed in an overexcited state as in the conventional case.

〔Effect of the invention〕

As explained above, this invention changes the voltage that operates the regenerative voltage absorption device in conjunction with the command voltage, so the regenerative voltage is kept low in areas where the command voltage is low, and overexcitation of the motor does not occur. This has the effect of not generating heat in the motor due to regeneration.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a graph showing characteristics of the device shown in FIG. 1,
FIG. 3 is a circuit diagram showing an example of a conventional device, and FIG. 4 is a graph showing characteristics of the device shown in FIG. 1...Control circuit, 2...Motor, 3...Chopper, 4...Capacitor, 5...Inverter, 6...
...Transistor, 7...Resistor, 8...Regenerative voltage absorption circuit, 10...Comparison circuit, 20...Addition circuit,
21...Reference voltage.

Claims (1)

[Claims] 1 A DC voltage generator generates a DC voltage according to the command voltage, converts this voltage into an AC voltage with the optimum frequency, and supplies it to the motor.When the regenerative voltage exceeds a predetermined voltage when the motor is stopped, the regenerative voltage is activated. In a power supply device that absorbs regenerative voltage in a voltage absorption device, there is a comparison voltage generation circuit that generates a comparison voltage by adding a certain voltage to the command voltage, and a comparison voltage generation circuit that operates the regeneration voltage absorption device when the regeneration voltage becomes higher than the comparison voltage. A power supply device equipped with a comparison circuit for