JPH02179481A - Apparatus for detecting missing phase of three-phase power source - Google Patents

Abstract

PURPOSE:To make the apparatus compact and to improve reliability by comparing the output voltage from a detecting circuit for three-phase currents with a present constant reference voltage value, and comparing the voltage with a proportional reference voltage value which is present in correspondence with an output voltage value and the like. CONSTITUTION:Of output lines 1a, 1b and 1c of a three-phase power source 1, it is assumed now that a current detector 4 is connected to the V-phase output line 1b. The detector 4 supplies the output voltage to first and second comparator circuits 5 and 6 in correspondence with the detected current value. In the circuit 5, the output from the detector 4 is compared with the constant reference voltage level from a lowest-level setting circuit 7. The output of the result of the comparison is supplied to an OR circuit 8. The output of a frequency controller 24 in an inverter circuit 2 is supplied to a missing-phase-judging-level output circuit 9, and the proportional reference voltage value corresponding to the output frequency of the inverter is guided out and supplied to the circuit 6. When the output of either of the circuit 5 or 6 is introduced into the circuit 8, the OR circuit 8 guides out and supplies an operation stopping signal C for the circuit 2.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention provides a three-phase power supply system that detects the presence or absence of phase loss in a three-phase power supply that supplies power to a load such as an air conditioner via an inverter circuit. This invention relates to improvement of a phase power supply open phase detection device.

(Prior Art) Conventionally, inverter circuits have been employed to drive and control three-phase AC motors of air conditioners and the like.

The inverter circuit basically consists of a rectifier, an inverter, a frequency controller for controlling the inverter, and the like, and controls how the load is supplied to the motor based on the frequency.

A three-phase (AC) power supply that supplies power to a load via an inverter circuit does not have any problems during normal operation, but the output of one or two of the three phases often decreases or stops due to a failure.

In such a case, measures such as stopping the output of the inverter circuit, etc. are taken in order to detect the phase as an open-phase state at an early stage and prevent the abnormality from having an adverse effect on the load.

Conventionally, in order to detect the presence or absence of an open phase in a three-phase power supply, a complicated configuration has been adopted in which the voltage of each output phase is constantly detected to determine whether it is normal or not. However, in conventional configurations like this, a voltage detection circuit is added for each phase, which results in a large-scale circuit configuration and a large number of circuit components, making it difficult to improve the reliability of the detection circuit itself. This was a contributing factor to the decline.

At the same time, the volume occupied by the detection device becomes large, which does not meet the demand for miniaturization of the entire air conditioner, for example.

(Problems to be Solved by the Invention) The conventional three-phase power supply open-phase detection device additionally includes a voltage detection circuit for each phase, resulting in problems such as complication of the device and reduction in reliability.

This invention detects only the three-phase current of any one phase and determines whether there is an open phase based on this detection signal, and the three-phase power supply is designed to reduce the size of the device and improve reliability. An open phase detection device is provided.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a three-phase power supply phase loss detection device that detects the presence or absence of a phase loss in a three-phase power supply that supplies power to a load via an inverter circuit. A detection circuit that detects the current of any one of the three phase currents supplied to the inverter circuit from the phase power supply and derives the corresponding voltage, and a detection circuit that is connected to this detection circuit and has an output voltage and a preset constant reference voltage. and a second comparison circuit connected to the detection circuit and comparing the output voltage value with a proportional reference voltage value preset corresponding to the inverter circuit output frequency. It is characterized by

(Function) The three-phase power supply open phase detection device according to the present invention, when at least one of the three phases is open, detects not only the current value of the corresponding phase but also the current value of the other normal two phases. The device is constructed by taking advantage of the fact that the current value of a phase or even one phase is affected.

Therefore, in any combination of phase open states, by detecting the output current value of any one phase and comparing and determining the current value according to the state classification, it is possible to accurately detect whether a phase open state has occurred. This is what I am trying to do.

Therefore, by providing a detection circuit that detects the power supply output current of any one phase and comparing the output signal from this detection circuit with two comparison circuits corresponding to each combination of lack conditions, it is possible to detect the total lack. Phase states can be detected accurately.

(Example) Hereinafter, an example of the three-phase power supply phase failure detection device according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

That is, the output lines 1a and 1 of each U, V, and W phase of the three-phase power supply 1
b and lc are respectively supplied to the inverter circuit 2.

The inverter circuit 2 includes a rectifier 21.degree. LC filter 22. It is composed of a constant voltage inverter 23, a frequency controller 24, etc., and the output of the inverter 23 is supplied to the three-phase motor 3, which is a load.

Said 3-phase electricity II! 1 output lines 1a, 1b, lc,
It is now assumed that the current detector 4 is connected to the V-phase specific force line 1b.

Does current detector 4 detect this? It derives the output voltage corresponding to the li current value, and the output voltage is divided into the first
．． The signal is supplied to second comparison circuits 5 and 6.

In the first comparison circuit 5, the output from the current detector 4 is compared with a constant reference voltage level A from the lowest level setting circuit 7, and the comparison output is supplied to an OR circuit 8. Since the reference voltage level A is independent of the inverter output frequency, it can be shown in FIG. 2 as A (constant reference voltage value).

On the other hand, the output of the frequency controller 24 of the inverter circuit 2 is supplied to the phase loss determination level output circuit 9, and a frequency control signal, that is, a proportional reference voltage value B signal corresponding to the inverter output frequency is derived. It is supplied to comparison circuit B.

Here, the phase-opening determination level output circuit 9 can be configured with a so-called F-V converter, and as shown in FIG. 2, the phase-opening determination level output voltage B proportional to the inverter output frequency is
is derived.

The OR circuit 8 output signal is the first and second comparison circuit 5.
When at least one of the output signals of 6 is introduced,
It derives and supplies an operation stop signal C to the inverter circuit 2.

The operation of the apparatus of the present invention having the above configuration will be explained below.

First, for each phase of U, V, and W of the 3-phase power supply l, open phases are marked with an X mark (normal phases are marked with an O mark), and examples of combinations of open phases are represented as shown in Figure 3. There are 7 ways (#1 to 7). Furthermore, in the combination shown in FIG. 3, considering the example of phase loss from #1 to #5, since the output current is currently being detected in the V phase, #1, 2. 4. For #5, open phase detection is performed unconditionally due to a drop in current value, etc., and for #3, there are other cases as well.

Since the W phase is open at the same time, a normal current value is not detected in the remaining V phase, and it can be determined that the three-phase power supply l has an open phase.

On the other hand, in the case of #6 and #7, only one of the U or W phase is open, but in this case, the current value rises above the normal value.

During normal operation, the inverter circuit 2 has a characteristic that the inverter input current (i.e., the output current of the three-phase power supply 1) increases in proportion to the inverter voice power frequency, as shown in FIG. For #6 and #7, V phase output line 1
Since a current higher than the characteristic curve (shaded area) flows through b,
By detecting the presence or absence of the increased current, the three-phase power source l
It is possible to detect the presence of an open phase. From this, the shaded area in FIG. 4 can be said to be an open phase determination area.

For this reason, the phase loss determination level output circuit 9 introduces the inverter output frequency signal from the frequency controller 24,
In order to identify whether or not the output voltage exists in the open phase judgment area (shaded area) in Fig. 4, the
(corresponding to the characteristic curve shown by the dotted line in the figure) is derived and supplied to the second comparison circuit 6 as the proportional reference voltage value B.

In this way, the first comparator circuit 5 compares it with a constant reference voltage A that is unrelated to the inverter output frequency set by the lowest level setting circuit 7, and if it does not reach level A, then It is determined that an open phase has occurred in one of the states #5, and a signal C indicating an operation stop, etc. is supplied from the OR circuit 8 to the inverter circuit 2.

In addition, in the second comparator circuit 6, the open phase is determined.
Even when a corresponding current value exceeding the determination curve (B) set by the open-phase determination level circuit 7 is detected, a signal C for stopping the operation, etc., is similarly derived via the OR circuit 8.

As described above, according to the present invention, except during normal operation, the first. The second comparison circuit can determine and detect as a linear function that a failure due to an open phase has occurred, and this detection signal can be used to promptly stop the inverter circuit, etc., and prevent the spread of an accident due to the failure. It is possible.

Note that in the above embodiment, the first. Although it has been explained that the operation of the inverter circuit 2 is stopped using the second comparison circuit output via the OR circuit 8, the present invention is not limited to this, and the three-phase power supply 1 itself may be cut off, or the operation of the inverter circuit 2 may be stopped. It goes without saying that a combination of protection measures may be taken.

As described above, the present invention provides an open phase detection circuit in only one location (
This can be achieved by simply configuring a comparator circuit or the like, and by using an IC circuit or the like, it is possible to realize a small, highly reliable device with a small number of parts.

[Effects of the Invention] As described above, the present invention reduces the number of current detection circuits that require high reliability and is constructed from a combination of simple logic circuits, etc., resulting in fewer failures and smaller size. It is possible to provide a three-phase power supply open-phase detection device, which has great effects in practical use.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of a three-phase power supply phase loss device according to the present invention, FIG. 2 is an operating characteristic diagram showing reference voltage characteristics with respect to inverter output frequency characteristics of the device shown in FIG. 1, and FIG. 1 is a combination diagram showing an example of an open phase in the device shown in FIG. 1, and FIG. 4 is an operational characteristic diagram of the inverter input current with respect to the inverter output frequency of the device shown in FIG. 1. l...Three-phase power supply 2...Inverter circuit 3...Motor 4...Current detector 5...First comparison circuit 6...Second comparison circuit 7...Level setting circuit 8... OR circuit 9... Phase loss judgment level output circuit agent Patent attorney Norio Ogo 1.31. b tsuboro, toki z raltg
Figure 1

Claims (1)

[Claims] In a three-phase power supply phase loss detection device that detects the presence or absence of a phase loss in a three-phase power supply that supplies power to a load via an inverter circuit, one phase of the three-phase current supplied from the three-phase power supply to the inverter circuit. a detection circuit that detects the current of the detector and derives a corresponding voltage; a first comparison circuit that is connected to the detection circuit and compares its output voltage with a preset constant reference voltage value; A three-phase power supply phase loss detection device comprising a second comparison circuit that compares an output voltage value and a proportional reference voltage value set in advance corresponding to an inverter circuit output frequency.