JPH0124036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control device for a reciprocating equipment drive motor that controls the starting operation of a reciprocating equipment drive motor such as a reciprocating compressor using an inverter.

[Prior art]

FIG. 1 shows the magnitude of starting torque with respect to the rotational angular position of a crankshaft, which is a drive shaft of a reciprocating compressor. As shown in the figure, the starting torque of a reciprocating compressor varies greatly depending on the crankshaft angle at the time of starting, but naturally, if the starting torque is large, the starting current of the drive motor also becomes large. Therefore, when variable frequency control is performed using an inverter, an inverter is required that has an output current capacity greater than the maximum starting current at maximum torque.
On the other hand, once started, the torque fluctuation due to the crankshaft angle is reduced due to inertia, and the input current to the compressor drive motor is reduced, so the inverter's output current capacity is This has the drawback of increasing the cost of the inverter.

[Summary of the invention]

This invention was made in view of the above points.The starting torque of the reciprocating equipment drive motor differs depending on the direction of rotation of the crankshaft, and since the starting torque of one of them becomes smaller, excessive inverter input current is detected by current detection. When a rotation direction in which the starting torque is large is detected, the starting torque is temporarily stopped, the starting torque is switched to a rotational direction in which the starting torque is small, and then restarted, even if the inverter has a small capacity. The present invention aims to provide a starting control device capable of controlling starting operation of a drive motor.

[Embodiments of the invention]

FIG. 2 is a block diagram showing one embodiment of the present invention, in which 1 is a commercial three-phase AC power supply, 2 is an AC power supply 1
3 is a smoothing capacitor, and 1, 2, and 3 constitute a DC power supply circuit 4. 5 is an inverter circuit, 6 is a three-phase AC output circuit of this, 7 is a control circuit that determines the generated frequency, phase rotation direction, output voltage value, etc. of the inverter circuit 5, and 8 is a control circuit that determines the generated AC of the inverter according to data from the control circuit 7. A control signal generation circuit 9 generates a PWM (pulse width modulated wave) waveform control signal that determines the output frequency, phase, and voltage value.
A forward/reverse switching circuit that switches the output phase of the waveform and the phase rotation direction of the three-phase AC output from the inverter circuit 5; 10 is a current detection circuit that detects an overcurrent of the DC input current of the inverter circuit 5 that is equal to or higher than a predetermined value; It is.

Next, its operation will be explained. The inverter circuit 5 switches the DC voltage according to the PWM waveform from the control signal generation circuit 8, and switches the DC voltage to the control circuit 7.
from the control signal generation circuit 8.
It generates an AC output with a frequency, phase, and voltage value determined by the PWM waveform, and energizes the reciprocating compressor drive motor.

First, when starting the compressor, the inverter circuit 5 is energized to generate an AC output that drives the compressor in the forward rotation direction. Now, if the angular position of the compressor crankshaft at this start-up is at θ ₁ in Figure 1, then
Since the direction of rotation is the direction in which the torque decreases, it can be started easily, and once started, the inertia allows it to overcome high torque points such as θ ₃ and accelerate. on the other hand,
If the angular position of the crankshaft at the time of starting is θ ₂ , the rotation direction is the direction in which the torque increases, and the starting torque at that position is also large, making it difficult to start.
A large starting current flows, which becomes an overcurrent of the DC input current of the inverter 5, which is detected by the current detection circuit 10. Upon receiving this detection signal, the control circuit 7 immediately stops the output of the inverter circuit 5. Then, after a certain period of time has elapsed, a signal is given to the forward/reverse rotation switching circuit 9 to reverse the phase rotation,
Restart the crankshaft in the opposite direction. If the crankshaft is rotated in the opposite direction, the rotation direction will be in the torque decreasing direction at the angular position θ ₂ of the crankshaft, and it will be possible to start it easily.

Although the above embodiment describes the case of driving a reciprocating compressor, it is clear that the present invention can be applied to driving other reciprocating equipment, and can also be used as a DC power source by rectifying commercial three-phase AC with a converter. Although an example has been shown, it is of course possible to use other DC power sources such as batteries.

〔Effect of the invention〕

Since this invention is configured as described above, always
The starting torque of reciprocating equipment such as compressors is reduced, and they can be rotated in a direction that is easy to start, so the configuration is simple, the output current capacity can be reduced, and the ratings of DC power supply circuits and inverter circuits can be lowered. This has the effect of reducing costs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the crankshaft angle and the starting torque at the time of starting a reciprocating device, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. In the figure, 4 is a DC power supply circuit, 5 is an inverter circuit, 6 is an AC output circuit thereof, 7 is a control circuit, 8 is a control signal generation circuit, 9 is a forward/reverse switching circuit, and 10 is a current detection circuit.

Claims (1)

[Claims] 1. A DC power supply circuit, an inverter circuit that is energized by this power supply circuit and obtains a multiphase AC output of a desired frequency, a generated frequency and voltage value of this inverter circuit,
A control circuit for setting the phase rotation direction, and a control signal generation circuit for generating a control signal for determining the frequency, phase, and voltage value of the AC output generated by the inverter based on data from the control circuit, Therefore, in a starting control device for a reciprocating equipment driving motor that starts, operates, and controls the reciprocating equipment driving motor, a current detection circuit that detects an overcurrent of a DC input current of the inverter that is equal to or higher than a predetermined value is provided. , a forward rotation/reverse rotation switching circuit configured to switch and output a control signal from the control signal generation circuit in response to a forward rotation signal and a reverse rotation signal from the control circuit to switch the phase rotation direction of the inverter;
This forward/reverse switching circuit starts the inverter in normal rotation according to the forward rotation signal from the control circuit at startup, and starts the motor of the inverter circuit by detecting overcurrent at startup by the current detection circuit. When the motor is restarted after being stopped for a predetermined period of time, the reciprocating equipment driving motor is controlled to switch the phase rotation direction of the inverter in response to a reversal signal from the control circuit. start control device.