JPH0479210B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention can be used for both single-phase motors and three-phase motors, and when used for single-phase motors, it protects the motor from open phase and overload current. The present invention relates to a motor protection relay that can further protect the motor from anti-phase operation when used in a three-phase motor.

(Prior art) A three-phase motor protection relay, generally called a 2E relay, detects the phase relationship from two-phase currents and determines whether there is an open phase. Since the open-phase pattern and the normal pattern of a single-phase motor are in the same mode, if a single-phase motor is connected to this relay as is, it will be mistakenly determined to be an open phase even though it is in a normal state, and the power will be disconnected. Therefore, it will operate as follows.
It cannot be used for single-phase motors.

On the other hand, some models are also available that can also be used for single-phase motors, but these use two of the three current transformers, and further switch to single-phase mode. It must be used as a relay, and a special wiring configuration is essential. Not only is it inconvenient to handle, but there is also a high risk of incorrect connection, making it difficult for anyone to use. It was a hassle to not be able to do it.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and it is possible to operate a relay in a normal state by simply selecting two wires and interposing a current transformer. It is an object of the present invention to provide equipment that can be used for both single-phase and three-phase applications, and to achieve ease of handling and expansion of the range of application.

(Means for Solving the Problems) To achieve this, the present invention, as shown in the block diagram of the configuration in FIG.
2 that is proportional to the motor current by intervening each in the main wiring
Two current transformers _1-1 , _1-2 that can take out the next current
When the single-phase motor or three-phase AC motor is started by a starting command, the secondary current of each of the current transformers is detected for a limited period of time from the start until the completion of the start. The starting current detection means 2, which operates when this current is zero current and outputs an open-phase signal, compares the phase of each secondary current of the current transformers _1-1 and _1-2 to determine whether there is an opposite phase. By comparing the phase of the secondary current in each current transformer _1-1 , _1-2 with the anti-phase detecting means 3 which outputs an anti-phase signal if the phase is anti-phase, the anti-phase is detected. It determines that the single-phase AC motor is connected under normal conditions and outputs a single-phase mode command, and if it detects that the phase is not reversed, it determines that the three-phase AC motor is connected under normal conditions. An operation mode switching means 4 that outputs a three-phase mode command, and when the single-phase mode command is output,
Select one of the two current transformers _1-1 and _1-2 , compare its secondary current with the set current corresponding to the full load current, and determine whether the secondary current is larger. For example, a single-phase open phase/overload detection means 5 outputs an overload signal as an open phase signal when the secondary current is zero, indicating an open phase state, and when the three-phase mode command is output. By comparing the phases of the secondary currents of each current transformer _1-1 , _1-2 and comparing the secondary current with a set current corresponding to the overload current, the current transformers 1-1, _1-2 are compared.
A three-phase open phase/overload detection means 6 that outputs an open phase signal if the phase in which _1-2 is not interposed is open, and outputs an overload signal if the secondary current is larger. ,
A motor protection relay is provided by an output unit 7 which generates an output to release the AC motor from the power supply, determining that the AC motor is in an abnormal operating state by outputting the open phase signal, the reverse phase signal, and the overload signal. It is composed of

(Function) With the above configuration, it is possible to correctly apply the motor to a single-phase AC motor or a three-phase AC motor without the need for any troublesome operations such as manual switching operations or wiring changes. It can be fully achieved.

(Example) Hereinafter, one example of the present invention will be described in detail with reference to the accompanying drawings.

Figure 4 is a block diagram of a motor protection relay, showing the two wirings connected to an AC motor (there is a three-phase motor _M3 and a single-phase motor _M1 ).
In other words, in the case of a three-phase motor _M3 , for example, the R phase and T
Phase wiring, for single phase motor _M1 , L phase N
As for phase wiring, two current transformers _1-1 and _1-2 are installed, and current transformers _1-1 and _1-2 are installed respectively.
Zero-cross pulse generation circuit _8-1 ,
_8-2 and electromagnetic switch for AC motor (not shown)
The interface 9 receives the signal _S1 that is transmitted in response to the input of the signal S1, and performs a logical product between the signal _S1 and the pulse P _T of the zero-cross pulse generation circuit _8-1 .
The AND circuit _10-1 calculates the logical product of the signal _S1 and the pulse P _R of the zero-cross pulse generation circuit _8-2 .
An AND circuit _10-2 , an overcurrent detection circuit 21, an input port _I0 receiving the output of the circuit 21, and both of the above-mentioned
Input ports I _{0 and} I ₂ receive the respective outputs of the AND circuits _10-1 and _10-2 , an output port O ₀ sends an overload signal to the output section 7 to be described later, and an output port O sends an open phase signal to the output section 7. Interface ₁ with each port with output port O ₂ which sends an anti-phase signal like 1
1, a power supply circuit 12 for supplying a DC constant voltage to each part, a clock circuit 13, a CPU 14, and a ROM 15, which have a measuring means and an arithmetic means and constitute each of the means 2, 3, 4, 5, and 6. , a central processing unit consisting of a RAM 16, an OR circuit 17, drivers _18-0 to _18-3 , an overload indicator _19-0 , an open phase indicator _19-1 , an anti-phase indicator _19-2 , and the electromagnetic switch. The input signal to the central processing unit is a signal S that is transmitted when the electromagnetic switch is turned on to energize the AC motor. ₁ ,
There are four signals of each output of the AND circuits _10-1 , _10-2 and the overcurrent detection circuit 21, and the signal _S1 is issued from the interface 9, which causes the CPU 14 to perform arithmetic processing (not shown) that has already been performed. is reset, and on the other hand, when the signal _S1 is being transmitted, one of the zero-crossing pulse generating circuits _8-1 and _8-2 transmits the pulse _PT or _PR , thereby causing the input port to be reset.
A signal is input to one of I ₀ and I ₂ and an arithmetic processing command is sent to the central processing unit.

As will be made clear in the operation description below, when an overload signal, an open phase signal, or an anti-phase signal is output from the central processing unit, if an overload signal is output, the driver _18-0 ~ _18-3 is activated and the overload indicator _19-0 lights up to indicate an overload, and at the same time, the output relay 20 is energized to open the electromagnetic switch to release the AC motor from the power supply and stop it. When a phase signal is output, the drivers _18-0 to _18-3 operate to indicate a phase failure by lighting the phase failure indicator _19-1 , and at the same time,
Energize the output relay 20 and open the electromagnetic switch 3
Release the phase AC motor from the power supply and stop it, while if a reverse phase signal is output, the driver 18
₋₂ to _18-3 are activated and the reverse phase indicator _19-2 lights up to indicate the reverse phase, and at the same time the output relay 20
The three-phase AC motor is operated to be energized, disconnect the three-phase AC motor from the power supply, and stop it.

By the way, to explain in principle how the above-mentioned protective relay operates in order to detect anti-phase and open phase states in the case of three phases, with reference to Fig. 2 A and B, T phase, R phase Zero-cross pulses are generated from the outputs of current transformers _1-1 , _1-2 provided in zero-cross pulse generating circuits _8-1 , _8-2 and input to the central processing unit.

Zero cross pulse of T phase selected as reference phase
A time measuring means such as an electronic counter is started by P _T1 , and the elapsed time t ₀ is determined when the zero cross pulse P _R1 is generated from the zero cross pulse generating circuit _2-2 associated with the current transformer _1-2 installed in the R phase. is measured and stored in the calculation means.

Furthermore, the electronic counter measures the elapsed time _t1 when the next zero-crossing pulse P _T2 occurs in the T phase, and stores it in the calculation means.

Unless there is a phase loss or an abnormal unbalanced state on the power supply side or the motor winding side, the phases of the T-phase and R-phase output signals (zero-cross pulses) will have a certain relationship, and the phase If the rotation is normal in a predetermined direction, the half-cycle equivalent time t ₁ corresponds to 180 degrees in electrical angle, and the elapsed time at the time of signal generation in the R phase with a difference of 120 degrees in electrical angle (t ₂ = t ₀ ) There is t ₂ between
= 2/3t ₁ If the relationship of 1 is established and the phase rotation is in the opposite direction, the elapsed time (t ₃ = t ₀ ) at the time of signal generation in the R phase with a 60° difference in electrical angle is In between
The relationship t ₃ =1/3t ₁ holds true.

This condition is when maintaining an equilibrium state in three-phase rotation, and for example, the voltage unbalance rate is 2%.
If the current unbalance rate is allowed up to 20% (to enable detection even under no-load conditions), the current unbalance rate will be approximately 20% (see Figure 3), and the phase angle deviation between the phases up to this unbalanced state is assumed to be acceptable. We calculated the phase angle tolerance and found that it was approximately 20°.

Therefore, the time △t, △ corresponding to this allowable phase angle
t = 20/360 x t ₁ = 1/18・t ₁ The range of the area added/subtracted from each of the above times t ₂ and t ₃ is the area of positive phase or anti-phase, and If it is in a region other than that, it will naturally be an open phase (open phase in a broad sense, including cases other than cases where a certain phase has completely zero current).

Therefore, it is normal within the range of the positive phase time relationship shown by the formula t ₂ = △t≦t ₀ ≦t ₂ +△t, and t ₃ −△t≦t ₀
Within the range of the antiphase time relationship shown by the formula ≦t ₃ + △t, it is antiphase and otherwise it is phaseless, so the calculations based on both of the above formulas are calculated using a calculation means, and according to the results. What is necessary is to emit an anti-phase signal or an open-phase signal.

Incidentally, when an open phase occurs in the T phase, which is the reference phase, a start command is not issued to the timing means, so this is treated as an open phase state.

However, as mentioned above, there are two types of open phase patterns: open phase on the power supply side and open phase on the motor side.
Phase loss on the power supply side is classified into five types as shown in C and D and E, respectively.

Assuming that there is a disconnection at the X mark of line B in Figure 5A, if current transformers are installed in lines A and C, the phase angle between A and C phases is 180°, which is an opposite phase, so it is considered as an open phase. If current transformers are provided in lines A and B or lines B and C, the B phase is at zero potential, so it can be detected as an open phase.

Also in FIG. 5B, the open phase can be detected for the same reason as in FIG. 5A, except that the motor connections are star-shaped and triangular.

In Fig. 5C, no matter which two phases of lines A, B, and C are provided with current transformers, a phase shift occurs as is clear from the vector diagram.
An open phase can be detected as being outside the conditions for normal and anti-phase.

In Figure 5 D, if current transformers are installed in lines A and B or lines A and C, the A and B phases and the A and C phases are all in opposite phases, as is clear from the vector diagram. On the other hand, if current transformers are provided in lines B and C, this can also be detected as an open phase because the B and C phases are in phase.

In addition, in FIG. 5E, the only difference is that the motor connections are star-shaped and triangular, and an open phase can be detected for the same reason as in FIG. 5D.

As described above, it is possible to detect open phase and antiphase in all cases.

In the protection device that performs the detection and protection operations described above, the operation in the central processing unit is shown in Fig _{. 6} . The timing means determines whether the zero-cross pulse P _T1 (phase) has been received (a), and if it has not been input, it synchronizes to the transmission of the clock pulse or gives repeated check instructions (b), (c),
Even if it is determined whether a signal has been input based on (d) (b) and the number of checks corresponding to the set number of times _N1 , that is, about 0.5 to 3 seconds, is performed,
When it is determined that the pulse signal P _T1 is not input (D), the output port O ₁ is read (Y), and an open phase signal is emitted from the output port O ₁ (R). This means an open phase in the T phase.

On the other hand, when it is determined that the pulse signal P _T1 has been input to the input port _I1 , it starts the clocking means (e) and reads the input port _I2 to check whether the pulse signal P _R1 has been input or not. phase (R
Determine whether or not the zero cross pulse P _R1 (phase) is received (f), and if it is not input, repeat the judgment (f) based on the repeat check instructions (b), (c), and (d), and set 0.5. If it is determined that the pulse signal P _R1 is not input even after ~3 seconds have elapsed (d), the output port _O1 is output one after another (y), and the open phase signal is emitted from the output port _O1 . This means an open phase of the R phase.

If it is determined that the pulse signal P _R1 has been input midway through (f), the timer means reads the time t ₀ at that time, and the time t ₀ is stored in the register (g).

Next, read the input port I ₁ and output the pulse signal.
Determine whether or not P _T2 has been input (ch), and if not, 0.5 based on check instructions (b), (c), and (d).
The determination is repeated for ~3 seconds (H), and when it is determined that there is no input (D), the output port _O1 is read (Y), and an open phase signal is issued from the output port _O1 . This means that an open phase of the T phase has occurred.

When it is determined that the pulse signal P _T2 has been input before reaching 0.5 to 3 seconds, the time measuring means is stopped, the time _t1 at that time is stored in the register, and the time measuring means is cleared ( li).

Next, the formula t ₂ of the positive phase time relationship is calculated using the calculation means.
=△t≦t ₀ ≦t ₂ +△t, that is, 11/18t ₁ ≦t ₀ ≦13/18
An operation is performed to determine whether the condition of t ₁ is satisfied (No).

If it is determined that this calculation result satisfies the condition (No), it is normal, neither phase inversion nor phase loss, so the counter J that counts the number of calculations by the calculation means is reset (R) and again (B) ~ The time measurement and arithmetic processing in (J) are performed every cycle.

On the other hand, if it is determined that the condition is not satisfied as a result of the calculation, the counter J is counted by one and the timing and calculation processes of (a) to (k) are repeated again.

Then, as a result of the condition continuing to be unsatisfied, when it is determined that the count number of the counter J has reached the set number of times N ₂ , the following calculation means is used to calculate the antiphase time relationship equation t ₃ −△t≦ An operation is performed to determine whether the condition t ₀ ≦t+Δt, that is, 5/18t ₁ ≦t ₀ ≦7/18t ₁ is satisfied (f).

When it is determined that this calculation result satisfies the condition (f), it reads the output port O ₂ (t),
Emit an anti-phase signal from output port O ₂ (S).

On the other hand, it is determined that the condition is not satisfied (f), and it is determined that the motor starting completion time Ts seconds has elapsed (f).
Then, the output port O ₁ is read (Y), an open phase signal is emitted from the output port O ₁ (R), and when it is determined that Ts seconds have not elapsed (N), the counter J
is reset (na), and the timing and arithmetic processing of (a) to (nu) are performed again every cycle.

Thus, based on the transmission of the open-phase signal (R) and the transmission of the anti-phase signal (S), the output section 7 generates an output for stopping the three-phase AC motor M.

It can now be understood that in the case of a three-phase AC motor, open _phase and anti-phase can be detected from the values and phases of the secondary currents of the two current transformers 1-1 and _1-2 . However, in the case of single-phase mode as opposed to three-phase mode, both current transformers _1-1 and _1-2 exhibit zero current in an open phase state;
Current transformer 1
Since open phase can be determined by detecting the presence or absence of either one of the secondary currents _-1 and _1-2 , open phase detection in single-phase mode is extremely simple.

On the other hand, in the case of a single-phase motor, overload current can be detected by detecting only one phase current.
In the case of a three-phase motor, this can be done by detecting two-phase currents.

Next, to determine whether it is single-phase operation or three-phase operation, in the case of single-phase operation, the current value is a normal value below the set current that does not cause overload, and the zero-cross pulse generation circuit _8-1 , Single-phase operation can be determined by the state in which pulses are generated simultaneously from _8-2 , that is, the reverse phase state.On the other hand, the state in which pulses are not simultaneously generated from the zero-cross pulse generation circuits _8-1 and _8-2, ie, the reverse phase state, can be determined. If the current value is a normal value less than or equal to the set current in a state where the phases are not reversed, it can be determined that three-phase operation is being performed.

The operating state of the motor protection relay is summarized by the flow diagram shown in FIG. 7, which is summarized below.

When it is determined that the electromagnetic switch is turned on and the AC motor is energized (a), the input port _I0 is read and the secondary current of current transformers _1-1 and _1-2 is sampled (b). , detecting whether current is flowing
If (c) is completed, and if the current is zero, it is determined that the value is zero for a predetermined number of consecutive times (d). Since this is the case, the starting current detection means 2 generates an open-phase signal and outputs an open-phase output from the output port _O1 (N).

On the other hand, when the current is detected (c), the AC motor has started, so current transformers _1-1 , 1-2 and ₂ are activated for several seconds until the start is completed.
Anti-phase sampling (e) is performed to compare the phases of the next currents, and if an anti-phase state is detected, the anti-phase detection means 3 issues an anti-phase signal and the output port O ₂
The inverse phase output is sent from.

On the other hand, if it is detected that there is no anti-phase state, wait for several seconds until the start is completed (h), and then sample the operation mode switching means 4 (re).
and compare the phase of the secondary current.
If it is determined that the phase is negative and is less than the set current corresponding to the full load current (2), a single-phase mode command is issued and a transition is made to open phase/overload sampling (2).

On the other hand, if it is determined that the phase is not reversed and the current is below the above-mentioned setting current (l), a three-phase mode command is issued to shift to open phase/overload sampling (f).

In addition, if the current value is equal to or higher than the set current regardless of the presence or absence of reverse phase, it means that the three-phase motor is locked, the three-phase motor has an open phase lock, or the single-phase motor is locked, so a lock signal is generated (warning). ), for example, to send out the output from output port O ₀ .

When open phase/overload sampling (f) on the three-phase side is performed, as is clear from the above explanation, whether it is due to the secondary current of current transformers _1-1 , _{1-2 or} the open phase (y),
It is determined whether there is an overload (T), and on the other hand, if open phase/overload sampling is performed on the single phase side (R), it is determined from the secondary current of one current transformer whether there is a phase open or not (S). , determine whether there is an overload (T), and transmit an open phase signal (N) or an overload signal (N).

In this way, it is possible to automatically perform a protective operation that is suitable for the type of motor, regardless of whether it is a single-phase motor or a three-phase motor.

(Effect of the invention) Next, the effects of the present invention will be described.

(a) It is extremely convenient because it can be used for both single-phase and three-phase motors without any troublesome handling such as switching operations or wiring changes.

(b) Only two current transformers are required, which reduces costs, and when used to protect a single-phase motor, phase loss can also be detected, and the system can also protect other motors. It has the advantage that the usage conditions do not change at all depending on whether it is single phase or not.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIGS. 2A and 2B are explanatory diagrams relating to an example of the present invention, showing the occurrence states of zero-cross pulses in a normal state and in an anti-phase state. FIG. 3 is an explanatory diagram related to an example of the present invention, and is a voltage unbalance rate-current unbalance rate relationship diagram, FIG. 4 is a block diagram of an example of the present invention, and FIG. Each open-phase pattern diagram in a three-phase circuit, FIG. 6 is a flow diagram showing the operation mode of anti-phase and open-phase detection at three-phase in the central processing unit according to one example of the present invention, and FIG. FIG. 2 is a flow diagram showing the operation mode of a central processing unit according to an example of FIG. _1-1 , _1-2 ...Current transformer, 2...Starting current detection means, 3...Reverse phase detection means, 4...Operation mode switching means, 5...Single phase open phase/overload detection means ,6
... Three-phase open phase/overload detection means, 7... Output section.

Claims (1)

[Claims] 1. Two current transformers _1-1 and 1-2 are installed in each of the two wirings connected to the AC motor, and each of the current transformers 1-1 and _1-2 is installed to limit the time required for the AC motor to complete starting. a starting current detection means 2 which detects the secondary current of the current transformers _1-1 , _1-2 and outputs an open phase signal when the current is zero; and two of the current transformers _1-1 , _1-2.
Anti-phase detection means 3 that compares the phase of the next current to determine whether there is an anti-phase, and outputs an anti-phase signal if the phase is anti-phase.
Then, the phases of the secondary currents in each current transformer _1-1 and _1-2 are compared, and if a reverse phase is detected, a single-phase mode command is issued, and if a non-reverse phase is detected, a three-phase mode command is issued. When the single-phase mode command is output, the current transformer 1
Compare one of the secondary currents of _-1 and _1-2 with the set current, and if the secondary current is larger, set the overload signal to 2.
A single-phase open phase/overload detection means 5 outputs an open phase signal when the next current is zero, and when the three-phase mode command is output, the current transformers _1-1 and _1-2 2
Comparing the phase of the secondary current and comparing the secondary current and the set current, if the phase where the current transformers _1-1 and _1-2 are not interposed is an open phase, an open phase signal is output. three-phase open phase/overload detection means 6 that outputs an overload signal if the secondary current is larger than the set current;
The unit is characterized in that it is equipped with an output section 7 that generates an output for releasing the AC motor from the AC power supply by outputting each of the phase loss signals, the anti-phase signal, and the overload signals. Phase/three-phase motor protection relay.