JPS62155794A - Inverter - Google Patents

Abstract

PURPOSE:To perform an operation in a low frequency region and a quick adjustable-speed operation safely regardless of the state of load by adding manual torque boosting characteristics in which a voltage correction value is increased with the lowering of frequency. CONSTITUTION:The starting currents I0 of automatic torque boosting and input currents Im are inputted to an adder-subtractor 10, Im-I0 is obtained, and the result is inputted to a setter 12 for a correction factor K1 through an amplifier 11. The setter 12 inputs a correction value K1(Im-I0) to an adder 6. The adder 6 executes these addition so that output voltage V0 originally brought to a fixed value when the output frequency of an inverter is kept constant is corrected by the correction value K1(Im-I0), and outputs corrected output voltage through an amplifier 7. The level of a voltage command value increases during a period T when currents Im exceed I0.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter that enhances the torque characteristics of a motor in a low frequency region.

[Conventional technology]

Figure 6 shows the voltage/frequency butter/of the inverter output with a conventional motor as a load. In Figure 1, Po is the basic pattern 7, and P2 is the area of the adjustment pattern that is adjusted according to the load current, that is, the input current of the motor. If a load current larger than the set current value flows, the output
It operates to increase the voltage substantially equally over the entire range of output frequencies. In other words, the motor is automatically torque boosted. According to this automatic torque boost, the same inverter capacity (same rated output current)
It can handle heavy loads, and can be used in applications such as agitators and conveyors that are subject to heavy loads at startup but light loads during operation.
It is suitable for applications such as conovairs, where the load sometimes increases during steady operation, and the load stabilizes once the load is overcome.

[Problem that the invention seeks to solve]

Although the conventional inverter has the automatic torque boost function as described above, in the low frequency region, when the input current of the motor is low, the generated torque is less than the rated torque, as shown by curve a in FIG. Therefore, by detecting this input current, it takes a long time to increase the output voltage and further boost the torque as shown in curves 7 and 7 in Figure 7. , there was a delay in the detection response of the input current, which caused problems such as the torque boost not being able to be done in time, and the motor current becoming excessive, causing the motor to stop.

This invention was made to solve all of the above-mentioned problems, and provides an inverter that can realize a sufficiently large acceleration torque boost by using a manual torque boost characteristic together with a normal automatic torque boost characteristic in the low frequency range. The purpose is to obtain.

[Failure to solve the problem]

The inverter according to the present invention outputs a constant voltage/frequency pattern regardless of the magnitude of input current to the motor by manual setting using an ILT pressure/pressure wave frequency setting device, and also outputs a constant voltage/frequency pattern according to the magnitude of the input current. /t, which the frequency adjuster automatically outputs.

The configuration is such that the voltage/frequency pattern is corrected using a positive value.

[Effect]

The voltage/frequency setting device in this invention can be manually operated.
This is because it is possible to set voltage/frequency characteristics that increase the torque boost in the low frequency range of the output voltage and decrease the torque boost in the high frequency range.

By combining this characteristic with the conventional automatic torque boost characteristic, it is possible to increase the speed of torque boost throughout the entire low frequency range to high frequency range, and this can also be done without overexcitation of the motor. do.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a frequency setter, 2 is a soft start circuit, 3 is a frequency command circuit, 4 is a voltage command circuit, and 5 is a manual torque boost circuit that functions to increase the output voltage correction value as the frequency decreases. Voltage/frequency setter, 6 is an adder that adds the output voltage VO by manual torque boost and the correction value by automatic torque boost, which will be described later, 7
is an amplifier, 8 is a motor input current detection circuit, 9 is a current setting device that sets the starting current Io of the automatic torque booth, 10
1 is an adder/subtractor for adding and subtracting the input current Im of the motor and the starting current Io, 11 is an amplifier, and 12 is a setting device □ for the correction coefficient. Note that 13 is a voltage/frequency adjuster.

Next, the operation will be explained.

First, the frequency setter 1 sets the reference frequency fi stage at the rated torque of the motor, and based on this, the output frequency f is set from the frequency command circuit 3 via the soft start circuit 2. , obtains the output voltage Vo from the voltage command circuit 4. This voltage command circuit 4 is provided with a voltage/frequency setter 5, which allows a large acceleration torque to be obtained, especially in the low frequency region, depending on machine tools and conveyance machines that require cycle operation. Set the voltage/frequency pattern. This Batano is input to an adder 6.

On the other hand, the motor input current detection circuit 8 detects the motor current Im,
That is, the magnitude of the load current of the inverter is constantly monitored, and this is input to the adder/subtractor 10.

The automatic torque boost starting current (reference current) Io specified in the current setting device 9 is input to this adder/subtractor 10, and the magnitude of the input current Im with respect to the starting current Io is determined by addition/subtraction (Im-Io). , the result is input to the correction coefficient 1 setter 12 via the a/b 11t. FIG. 2 shows the relationship between this input current Im and the starting current Io.

In this setting device 12, 1 is set as a correction coefficient according to the load, and 1 (Im-1o) is inputted into an adder 6 as a correction value. This adder 6 performs these additions so that the output voltage Vo, which is originally a constant value if the output frequency of the inverter is constant, is corrected to a correction value (Im-Io), and the amplifier All of this is output via r2-. tsufv,
The level of the voltage command value increases as shown in FIG. 3 during the period T during which Im passes Io.

For this reason, the voltage/frequency pattern B manually set by the voltage/frequency setter 5 and the correction value set by the voltage/frequency regulator 13 are matched with the voltage/frequency pattern B based on the equation (Im-Io). The voltage/frequency characteristics shown in FIG. 4 are obtained, and the lower the frequency, the higher the output frequency f. The output voltage Voi can be set larger than the output voltage Voi.

As a result, the total input current of the motor in this low frequency region is increased, and the torque can be quickly increased to more than the rated torque, as shown by curve a in FIG. 5. Furthermore, if the torque is large and the motor slippage is small,
Since the input current also decreases, the output voltage of the inverter is returned to its original value. This is similar to the case of automatic torque boost only. In addition, in automatic torque boost, even if there is a delay in response to steep load fluctuations, a sufficiently large acceleration torque can be obtained by simultaneously executing one manual torque boost.

〔Effect of the invention〕

As described above, according to the present invention, the manual torque boost characteristic is added to the automatic torque boost characteristic in which the voltage correction value becomes larger as the frequency becomes lower. driving in the low frequency range and sudden acceleration/deceleration.

This has the effect of being able to be carried out safely regardless of the load condition, and reliably preventing occurrence of motor overcurrent due to response delay, as in conventional automatic torque boosting.

[Brief explanation of drawings]

FIG. 1 is a block connection diagram of an inverter according to an embodiment of the present invention, FIG. 2 is a time chart of the input current of the motor, FIG. 3 is a time chart of the output voltage, and FIG. 4 is a time chart of the output voltage/voltage. Similarly, FIG. 5 is a torque/current-all nine characteristic diagram, FIG. 6 is a conventional output voltage/frequency characteristic diagram, and FIG. 7 is a torque/current-all nine characteristic diagram. 3 is a frequency command circuit, 4 is a voltage command circuit, 5 is a voltage/frequency setter, 6 is an adder, 8 is a motor input terminal detection circuit%, 9 is a current setter for starting torque boost, 10 is an adder/subtractor, 12 13 is a correction value setter, and 13 is a voltage/frequency adjuster. Patent applicant: Mitsubishi Electric Corporation (2 others) 'Figure 2 Figure 3 Figure 4': l=l Go to T
) = Procedural amendment (voluntary)

Claims (2)

[Claims] (1) In an inverter that has the function of detecting the input current of a motor connected to the output side and adjusting the output voltage according to the current value, a constant voltage/frequency pattern is output regardless of the magnitude of the input current. Equipped with a voltage/frequency setter and a voltage/frequency adjuster capable of correcting the voltage/frequency pattern according to the magnitude of the input current based on the voltage/frequency pattern set by the voltage/frequency setter. An inverter characterized by: (2) When the motor input current exceeds the set value, the voltage /
2. The inverter according to claim 1, wherein the inverter corrects the frequency pattern.