JP2541188B2 - Phase loss detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an open-phase detection device for a three-phase AC circuit, and more particularly to a refrigeration for a refrigerating vehicle that can be operated by either a vehicle battery or an external three-phase AC power source. Phase detection device when an external three-phase AC power supply for a machine is used.

2. Description of the Related Art Conventional refrigerators for refrigerating vehicles, regardless of whether the compressor is driven by a vehicle engine or an auxiliary engine, are engine driven by noise, exhaust gas, etc. when the vehicle is stopped or moving on a ship. A device is provided to drive the compressor by means of a motor in case it cannot be driven. In this case, the power supply for the electric equipment of the refrigerator, including the compressor motor, uses an external AC power supply to avoid over-discharge of the vehicle battery.
Cooling fan motors, condenser fan motors, control circuits, etc., excluding compressor motors, must be of a DC power supply specification so that they can be operated with either an on-vehicle battery that is a DC power supply or an AC power supply. Is generally used as a direct current. In this case, the AC power supply in this case is not a single phase but a rectified one, considering the cost up and ripple voltage by installing a smoothing circuit.
Phase is used. In such a refrigerator, if the phase is lost due to a defect in the original power supply, a break in the power supply line, or a blown fuse, etc., the rectified voltage becomes a single-phase full-wave rectified waveform, causing an error in the control circuit. It is very unfavorable that the operation, the life of the cooling fan motor, the life of the condenser fan motor is shortened, and the compressor motor using the AC power supply is overloaded due to the single-phase operation. In contrast,
As a conventional open-phase detection method, for example, Japanese Patent Publication No. 53-2782
There are those disclosed in Japanese Patent No. 5 and Japanese Patent Publication No. 60-47816. The method according to Japanese Patent Publication No. 53-27825 is full-wave rectification of three-phase alternating current, and the potential difference between the highest potential and the lowest potential of each power supply line is the maximum of the single-phase AC voltage in the normal state where there is no open phase Focusing on the point that it does not fall below 3/2 times the value but always becomes zero when there is a phase loss, this potential difference is divided by a resistor and connected to the base of the transistor, and when this potential difference becomes zero, the transistor becomes " When it is turned off, the phase loss is detected. However, in such a system, even when the three-phase AC circuit is normal, the unbalance degree of the three-phase current increases, or when the load current enters the eddy current region and the pulsating component of the rectified output increases. There is a problem that it is difficult to distinguish between the normal state and the open phase state. In addition, Japanese Examined Japanese Patent Sho 60-4781
The method disclosed in Japanese Patent No. 6 uses the fact that the frequency of the ripple (pulsation) waveform is different at the time of positive phase and at the time of open phase, counts each frequency, and detects the open phase by detecting the difference, In this case, since the amplitude of the ripple (pulsation) waveform in the normal phase is very small, it is difficult to detect the frequency, and there is a problem that the influence of noise or the like is large and stable open phase detection cannot be obtained. Further, in the phase loss protection relay or the like which is generally commercially available, since the unbalanced portion of the load current is detected, there is a drawback that even if the phase is lost from the beginning, it cannot be detected unless it is moved once.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention is stable without being affected by unbalance of three-phase currents or load overcurrent that occurs during normal operation of a three-phase AC circuit, and particularly not affected by noise. It is another object of the present invention to provide a phase loss detecting device capable of detecting a phase loss.

Means for Solving the Problems Two detection circuits having different open-phase detection methods are provided in parallel, and one detection circuit is a filter circuit for extracting only the pulsating component from the rectified output of a full-wave rectification circuit, and this filter. A first comparison circuit that compares an output value from the circuit with a first predetermined reference value; a signal output circuit that outputs a signal corresponding to the frequency of the pulse waveform output from the first comparison circuit; A second comparison circuit that compares the output value from the signal output circuit with a second predetermined reference value.

The other detection circuit is an effective value conversion circuit that converts the rectified output of the full-wave rectification circuit into an effective value, and a third comparison that compares the output value from this effective value conversion circuit with a third predetermined reference value. And a circuit.

A determination circuit that determines whether or not there is a phase loss based on the outputs of these two detection circuits is provided.

Action In the one detection circuit, only the pulsating component is extracted from the rectified output of the full-wave rectification circuit by the filter circuit,
The output value from the filter circuit is
Is compared with a predetermined reference value of. Then, a signal corresponding to the frequency of the pulse waveform obtained by comparing these is output from the signal output circuit, and the output value from this signal output circuit is compared with the second predetermined reference value.

In the other detection circuit, the rectified output of the full-wave rectifier circuit is converted into an effective value by the effective value conversion circuit, and the output value from the effective value conversion circuit is converted into the effective value by the third comparison circuit.
Is compared with a predetermined reference value of.

Then, one of the detection circuits has a result that the output value from the signal output circuit is larger than the second predetermined reference value, or the other detection circuit has a third predetermined reference value. If the output value from the RMS conversion circuit is smaller than the value, the determination circuit determines that the phase is missing. By this, the open phase can be detected.

Embodiment 1 FIG. 1 is a block diagram of a detection device 21 according to an embodiment of the present invention, in which a three-phase AC output from a three-phase AC circuit 26 is full-wave rectified by a full-wave rectifier circuit 18 and output. Its output is 2
One is the filter circuit 29 and the other is the first comparison circuit 2
8, a reference voltage setting circuit 16 for setting a first reference voltage, a frequency-voltage conversion circuit 2 as a signal output circuit, a reference voltage setting circuit 3 for setting a second reference voltage, and a second comparison circuit 4. It is connected to the first detection circuit. The other output of the full-wave rectifier circuit 18 is connected to a second detection circuit including an effective value conversion circuit 5, a reference voltage setting circuit 13 that sets a third reference voltage, and a third comparison circuit 6. The first of these
And the output of the second detection circuit is input to the AND circuit 7 as a determination circuit.

To explain the operation, the rectified output of the full-wave rectifier circuit 18 includes a small pulsation under normal conditions, as shown in the waveform diagram of FIG.
The waveform becomes 9a, and when the phase is lost, it becomes 11a. In one of the detection circuits, passing the filter circuit 29 having the capacitor 1 to extract the pulsating component of the rectified output (AC coupling with the capacitor 1) results in the third waveform. Has a waveform of 15a, and the amplitude of the waveform is different between the normal phase 14a and the open phase 15a, and becomes large during the open phase. By using this, when the first reference voltage 16a is set by the reference voltage setting circuit 16 so as to never cross the waveform 14a at the time of normal, and always cross the waveform 15a at the time of open phase, the reference voltage 16a is When it crosses, it becomes a missing phase. However, if the reference voltage 16a is crossed for a moment even though it is normal due to noise or the like, it is determined that the phase is missing. In order to reduce such erroneous detection, the frequency-voltage converter 2 detects the frequency of a portion across the reference voltage 16a output from the first comparison circuit 28 (generally, the frequency of the AC power supply is 50 Hz or 60 Hz). Therefore, by full-wave rectification, it becomes 100Hz or 120Hz when there is a phase loss.) And converts it to a voltage. This voltage and the reference frequency of the reference voltage setting circuit 3 (must be smaller than 100Hz, but if it is set too small, it may cause malfunction due to noise of the power supply. Also, if it is too close to 100Hz, the power supply frequency thereby causing malfunction due to the error. in view of these, around 80Hz is considered reasonable.) equivalent of a reference voltage (to V ₃₎ compared by the second comparator circuit 4 reference frequency corresponding reference If the voltage is V ₃ or more, it is determined that the phase is open. According to this detection method, noise is superimposed on the waveform 14a having a small amplitude in a normal state, and even when the noise may cross the reference voltage 16a, the frequency at the time of frequency-voltage conversion becomes an extremely low value, so that noise is generated. Therefore, it is possible to avoid the problem that the normality is determined as the missing phase. However, when the frequency-voltage conversion circuit 2 is actually used, several tens of times are present when the power is turned on due to the circuit configuration.
There is an operation delay from msec to several 100 msec. Therefore, even if the phase is lost from the beginning, there is no output voltage from the frequency-voltage conversion circuit 2 due to an operation delay when the power is turned on. Therefore, the reference voltage V ₃ corresponding to the reference frequency is compared with the second comparison circuit 4. As a result, it is judged to be normal. However, when the frequency-voltage conversion circuit 2 is in the operating state, the output causes a phase loss voltage, and the second comparison circuit 4 generates a reference voltage V ₃ corresponding to the reference frequency. Compared with the above, the voltage output from the output of the frequency-voltage conversion circuit 2 is higher, and it is determined that the phase is missing.

In order to eliminate such inconvenience, the other open phase detection is performed by the other detection circuit. In this detection method, the full-wave rectified output is passed through the effective value conversion circuit 5 to generate the full-wave rectified output as shown in FIG. The normal value of the full-wave rectified wave 9a has a high voltage such as 10a, and the effective value of the full-wave rectified wave 11a during the open phase has a low voltage such as 12a. Both of these voltages 10a and 12
A third reference voltage 13a is provided between a and by the reference voltage setting circuit 13, and the reference voltage 13a and the effective value are compared by the third comparison circuit 6. If the effective value is higher than the reference voltage 13a, it is normal, and if it is lower. Judge as a missing phase. In this method, when the phase is lost from the beginning, the output voltage of the effective value conversion circuit 5 is low due to the delay of the effective value conversion by the effective value conversion circuit 5 when the power is turned on, and the third comparison circuit 6 causes the reference voltage to decrease. Since it is lower than the reference voltage 13a as compared with 13a, the phase is judged to be open. After that, even if the effective value conversion circuit 5 is in a normal operating state, the output voltage is low because it is out of phase, and when compared with the reference voltage 13a by the third comparison circuit 6, it is lower than the reference voltage 13a, so it is determined to be out of phase. In addition, the detection method by the effective value conversion in the second detection circuit, due to variations in the power supply voltage value, transformer performance, rectifier performance, etc., causes the open-phase waveform 15a to fall below the reference voltage 16a corresponding to the reference frequency, depending on the frequency. Even if the phase loss detection does not operate, there is an advantage that the phase loss can be detected. However,
Only the detection method by rms value conversion has an rms value of 10a in the positive phase.
When the difference between the effective value 12a at the open phase and the open phase is small, it is difficult to accurately distinguish the positive phase and the open phase.

Therefore, the two methods are used together, the output from one detection circuit and the output from the other detection circuit are connected to the AND circuit 7, and it is determined that there is a phase loss when at least one of the detection circuits detects a phase loss. .

FIG. 4 is a block diagram when the open-phase detector 21 of the present invention is used as a open-phase protector for an on-vehicle refrigerator.

The three-phase AC circuit 26 is connected to the transformer 17 and is a refrigerator circuit.
It is lowered to the voltage required for 30 (12V or 24V) and full-wave rectified by the full-wave rectifier circuit 18. The full-wave rectified wave is taken in by the open-phase detection device 21 and the open-phase detection is performed as described above.
Two types of phase loss detection methods are used, and when at least one of the detection circuits detects the phase loss and determines that there is a phase loss, the relay coil 19 is de-energized and demagnetized. Then, the contact 20 opens and the relay coil 22 is not energized, the contact 23 returns to the battery 25 side, and the refrigerator circuit 30 does not operate unless the switch 24 is inserted. The power supply 27 of the open-phase detector 21 and the power supply of the relay coil 19 are DC power supplies.
May be supplied from 25.

EFFECTS OF THE INVENTION As described above, in the present invention, one of the detection circuits has a result that the output value from the signal output circuit is larger than the second predetermined reference value, or the other detection circuit has the result. Then, when the result that the output value from the RMS conversion circuit is smaller than the third predetermined reference value is obtained, it is determined that the phase is open. Therefore, the shortcomings of the respective detection circuits are covered with each other, and the accuracy of open phase detection is synergistically improved, and the pulsating component of the rectified output is increased due to the imbalance of the three-phase current or the overload current, or the noise is generated. Even in some cases, the open phase can be detected reliably and stably without being affected by these.

[Brief description of drawings]

FIG. 1 is a phase loss detecting device according to an embodiment of the present invention, and FIG.
Waveform diagram of full-wave rectified output of three-phase AC at normal and open phase,
FIG. 3 is a waveform diagram of the full-wave rectified output when the filter (AC coupling of the capacitor) is normal and when there is a phase loss. FIG. 4 shows the phase loss detection device of FIG. It is a block diagram when it is used for. In the figure, 1 ... Capacitor (filter circuit), 2 ... Frequency-voltage conversion circuit, 3 ... Second reference voltage setting circuit, 4 ... Second comparison circuit, 5 ... Effective value conversion circuit, 6 ...... Third comparison circuit, 7 ... AND circuit, 13 ... Third reference voltage setting circuit, 16 ... First reference voltage setting circuit, 18 ... Full wave rectification circuit, 21 ... Open phase detection Device, 26 …… three-phase AC circuit, 29 ……
Filter circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masami Kamata, 1-1, Showamachi, Kariya city, Nihon Denso Co., Ltd. (56) References: 58-95143 (JP, U) (JP, U)

Claims (1)

(57) [Claims] 1. A full-wave rectifier circuit for full-wave rectifying the current or voltage of a three-phase AC circuit, a filter circuit for extracting only pulsating components from the rectified output of this full-wave rectifier circuit, and an output value from this filter circuit. A first comparison circuit for comparing with a first predetermined reference value, a signal output circuit for outputting a signal corresponding to the frequency of the pulse waveform output from the first comparison circuit, and an output from this signal output circuit A second comparison circuit that compares the value with a second predetermined reference value, an effective value conversion circuit that converts the rectified output of the full-wave rectification circuit into an effective value, and an output value from this effective value conversion circuit. As a result of comparison between the third comparison circuit for comparing with the third predetermined reference value and the second comparison circuit, the output value from the signal output circuit is larger than the second predetermined reference value. If the condition is met, or if the third As a result of the comparison performed by the comparison circuit, when the condition that the output value from the effective value conversion circuit is smaller than the third predetermined reference value is satisfied, the phase loss determination circuit determines the phase loss. Detection device.