JPH0258850B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a protection circuit for an emergency AC power supply device that converts DC power of a battery into AC power during a power outage.

(Prior Art) Inverters that use power transistors or the like as switching elements in the output stage have a capacitor connected to the AC output side in order to absorb spike voltages that occur when switching the switching elements.

However, when the inductive load connected to the AC output terminal is opened, the switching element directly charges and discharges this capacitor, causing an excessive current to flow. There is a risk that the switching element will be destroyed.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to promptly stop the operation of the inverter after the load is released, and protect the switching elements. It is.

(Means for Solving the Problems) The present invention provides a switching element connected between one end of a DC power source and an AC output terminal, a switching element connected between an AC output terminal and the other end of the DC power source, and an AC output terminal. In a protection circuit for an emergency AC power supply using an inverter having a spike voltage absorbing capacitor connected between a terminal and the other end of the DC power supply, and controlling the switching of the switching element, Insert the chiyoke coil,
The present invention is characterized in that a terminal voltage of the choke coil is detected, and when the terminal voltage exceeds a predetermined value, the inverter is stopped.

(Example) FIG. 4 is a general explanatory diagram when the emergency three-phase AC power supply device according to the present invention is used. In the figure, indicates an emergency three-phase AC power supply, a control panel for controlling the load, and a load.

FIG. 1 is a circuit diagram of one embodiment of the emergency three-phase AC power supply device 1 shown in FIG. It is something that will be done. In Fig. 1, R _I , S _I , and T _I indicate three-phase commercial input power supply, and during non-power outage, electromagnetic switch MC ₁
It is connected to the connection terminal section P of the shutter hoist switchboard etc. via the contact point of the shutter hoist switchboard. R, S, of terminal part P
T is a load connection terminal. r, s, and t are AC output terminals.

O is an oscillator, which in this embodiment generates a 360 Hz rectangular wave. The oscillation output of oscillator O is sent to the clock inputs CK ₁ and CK ₂ of shift registers SH ₁ and SH ₂ .
Shift registers SH ₁ and SH ₂ transfer the contents of data inputs D ₁ and D ₂ to outputs Q ₁ to Q ₆ , respectively, by shift pulses from the clock inputs. Here, the output Q ₃ of shift register SH ₁ is
is fed back to the data input _D1 through the NOR gate _G1 , resulting in shift register _SH1 ,
The outputs Q ₁ to _{Q 6} of SH ₂ are six-phase signals as shown in FIG.

The outputs Q ₁ to _{Q 6} of shift registers SH ₁ and SH ₂ are
Transistors Tr ₁ , _{Tr 4 ,}
Added to the base of Tr ₇ , Tr ₁₀ , Tr ₁₃ and Tr ₁₆ .
Transistors Tr ₁ , Tr ₄ , Tr ₇ , Tr ₁₀ , Tr ₁₃ , Tr ₁₆
is connected to the primary side of transformers T ₁ to _{T 3} with center taps, and the secondary side of each transformer T ₁ to _{T 3} is connected to
Darlington-connected switching transistors Tr ₅ , Tr ₆ ; Tr ₂ , Tr ₃ ; Tr ₁₁ , Tr ₁₂ ;
Tr ₈ , Tr ₉ ; Tr ₁₇ , Tr ₁₈ ; Tr ₁₄ and Tr ₁₅ are connected. Therefore, as shown in FIG. 2, each transistor Tr ₁ to _{Tr 18} is connected to a shift register SH ₁ , SH ₂
Switching is performed in response to the output of the switching transistors Tr ₆ , Tr ₃ , Tr ₁₂ , Tr ₉ ,
As shown in FIG. 3, Tr ₁₈ and Tr ₁₅ output 60 Hz alternating current delayed by 2/3 π radian in electrical angle to the alternating current output terminals r, s, and t. In Figure 1, resistors R ₇ to R ₁₈ are used to flow an appropriate base current to each transistor, and the capacitors
C ₁ to C ₉ allow time during which current does not flow to the primary side of transformers T ₁ to _{T 3} so that the upper and lower transistors connected to the secondary sides of transformers T ₁ to _{T 3} conduct simultaneously. This is to prevent
In addition, the diodes D ₁ to _{D 6} are connected to the transistors T ₁ ,
It is for protection of Tr ₄ , Tr ₇ , Tr ₁₀ , Tr ₁₃ and Tr ₁₆ .
Switching transistors Tr ₆ , Tr ₃ , Tr ₁₂ ,
Diode D ₇ connected to Tr ₉ , Tr ₁₈ , Tr ₁₅
〜D ₁₂ and the capacitor C ₁₀ 〜C ₁₂ connected between the AC output terminals r, s, t and the ground line Gnd.
is a switching transistor when a load is connected.
This is provided to absorb the spike voltage that occurs when Tr ₆ , Tr ₃ , Tr ₁₂ , Tr ₉ , Tr ₁₈ , and Tr ₁₅ switch. Transistors Tr ₅ , Tr ₆ , Tr ₁₁ ,
The collectors of Tr ₁₂ , Tr ₁₇ , and Tr ₁₈ are connected to, for example, the + of 216V storage battery B via the choke coil CH ₁ .
side is connected. Transistors Tr ₃ , Tr ₉ ,
The emitter of Tr ₁₅ is connected to the ground line Gnd via the choke coil CH ₂ .

The operation will be explained.

In a non-power outage state, the 216V storage battery B is charged by the charging circuit C. A tap is taken out from the 24V point of storage battery B, which becomes the power source for operating the operating circuit. When there is no power outage, the shutter is raised or lowered by a switch (not shown) provided on a control panel connected to the terminal P. When emergency switch SW ₁ is closed, the relay is activated regardless of whether there is a power outage or not.
Ry ₁ is energized, the charge on capacitor C ₁₄ makes transistor Tr ₁₉ conductive, and relay Ry ₂ is energized. By energizing relay Ry ₂ , if switch MC ₁ is energized during a non-power outage, it is deenergized. Switch MC ₁ is naturally deenergized during a power outage.

When relay Ry ₂ is energized, voltage is applied to each gate and resistor by resistor R ₂₁ and Zener diode D ₁₇ , and oscillator O oscillates at 360 Hz. Immediately after the oscillator O starts operating, the input of the NOR gate _G3 is kept low by the resistor _R22 and the capacitor _C15 until several tens of milliseconds have passed, and the output of the NOR gate _G4 remains high, causing a shift. The outputs Q ₁ to _{Q 6} of the registers SH ₁ and SH ₂ remain at L. In addition, one input of the invert and gate _G2 is connected by resistors _R24 to _R26 and capacitor _C17.
It is kept low for 30 to 60 seconds, during which time the output of invert and gate G ₂ becomes high, keeping transistor Tr ₁₉ on and also connecting NOR gate G ₆ , invert AND gate G ₇ , and NOR gate
Clear _the shift registers SH ₁ and SH 2 through G ₄ and set CL ₁ and CL ₂ to L, and then clear the shift registers SH 1 and SH ₂ .
SH ₂ outputs as described above. In addition, the relay
When Ry ₂ is energized, the shutter winding motor is connected as a load to the output terminals R, S, and T of the terminal section P via the control panel so as to rotate in the direction of winding up the shutter. Transistors Tr _{1 ,} Tr ₄ , Tr ₇ , Tr ₁₀ , Tr ₁₃ and Tr ₁₆ are turned on and off based on the outputs Q ₁ to Q ₆ of shift registers SH ₁ and SH 2, and only when they are on, 24V is applied to the primary side of the transformer.
A current flows from the power supply, and a voltage induced in the secondary side of the transformer causes switching transistors Tr ₅ , Tr ₆ ; Tr ₂ , Tr ₃ ; Trr ₁₁ , Tr ₁₂ ;
Tr ₈ , Tr ₉ ; Tr ₁₇ , Tr ₁₈ ; Tr ₁₄ and Tr ₁₅ are turned on, and current flows through the switching transistors Tr ₆ , Tr ₃ , Tr ₁₂ , Tr ₉ , Tr ₁₈ , and Tr ₁₅ from the 216V DC power supply. .

When a load is connected, the output terminal r-s
Looking between the switching transistors
When Tr ₆ and Tr ₉ are conductive, from the + terminal of the DC power supply,
CH ₁ →Tr ₆ →r→R→Load→S→s→Tr ₉ →CH ₂
→Load current flows through the Gnd path. Also, when the switching transistors TR ₁₂ and TR ₃ are conductive,
Load current flows from the + terminal of the DC power supply through the path CH ₁ → Tr ₁₂ → s → S → load → R → r → Tr ₃ → CH ₂ → Gnd. Similarly, switching transistor
When Tr ₁₂ and Tr ₁₅ , Tr ₁₈ and Tr ₉ are conductive, the output terminal s
A load current flows between output terminals tr and t, and when switching transistors Tr ₁₈ and Tr ₃ , Tr ₆ and Tr ₁₅ are conductive, a load current flows between output terminals tr and three AC output terminals r, s, and t. A phase current is output. This energizes the electromagnetic switch MC ₂ , causing the shutter winding motor to rotate and open the shutter.

During winding of the shutter, that is, when a load is connected to the AC output terminal, a DC current flows in the same direction through the chain coil CH ₂ , but this current is the sum of the three-phase current supplied from the DC power supply, so The current value is almost constant, the magnetic circuit of the chioke coil is saturated due to DC excitation, its inductance is ignored, the voltage generated across it is small, and the voltage of capacitor _C13 is L.

When the shutter is fully opened, the motor is disconnected from the output terminals R, S, and T of the terminal section and stopped by an upper limit detection signal from a limit switch (not shown).

In such a state, the AC output terminals r,
No load is connected to s and t, resulting in a no-load state.

When there is no load, the switching transistors Tr ₆ and Tr ₉ are connected between the output terminals rs and rs.
When conducting, CH ₁ →
The capacitor C ₁₂ is charged along the path Tr ₆ → r → C ₁₂ → Gnd, and the charge in the capacitor C ₁₁ is discharged along the path C ₁₁ → s → Tr ₉ → CH ₂ → Gnd.
When the switching transistors TR ₁₂ and TR ₃ are conductive, CH ₁ →Tr ₁₂ →s→
The capacitor C ₁₁ is charged along the path C ₁₁ →Gnd, and the charge in the capacitor C ₁₂ is discharged along the path C ₁₂ →r→Tr ₃ →CH ₂ →Gnd. The same holds true when the other switching transistors are turned on, and as a result, the discharge current of the capacitors C ₁₀ to C ₁₂ flows through the chi-yoke coil CH ₂ as an intermittent pulse-like current, and due to its inductance, the chi-yoke coil CH ₂ A large voltage appears between the terminals.

The voltage across the terminals of the choke coil CH ₂ is rectified by the diode D ₁₃ and charges the capacitor C ₁₃ to H via the resistor R ₁₉ . Therefore, when the load is released, one of the inputs of the invert AND G ₂ becomes H through the resistor R ₂₀ , and the output of the invert AND G ₂ becomes L. The output of the invert AND _G2 makes the output of the NOR gate _G6 H via resistors _R27 and _R28 , and clears the shift registers _SH1 and _SH2 . Thereby, shift register SH ₁ ~ _{SH 2}
All outputs Q ₁ to Q ₆ are held at L. The switching operation of the switching transistor is stopped. This stopping operation occurs at the same time as the shutter winding motor leaves the output because the winding coil CH ₂ is included, and the switching transistor
Capacitors in Tr ₆ , Tr ₃ , Tr ₁₂ , Tr ₉ , Tr ₁₈ , Tr ₁₅
The switching transistor is protected from overcurrent by preventing the charging/discharging current of _C10 to _C12 from flowing directly.

By using this protection circuit, the switching capacitance of the switching transistor can be made as small as the current required for winding the shutter. When the circuit is stopped, the L output of the invert AND G ₂ turns off the transistor Tr ₁₉ , deenergizes the relay Ry ₂ , turns off the circuit's operating power, and stops the buzzer BZ.
The circuit goes into a standby state.

In addition, in the above-mentioned embodiment, the chiyoke coil
The opening of the shutter winding motor is detected by detecting the change in the voltage that appears at both ends _of CH ₂ when it is saturated and when it is unsaturated. This is the same as the current flowing through CH ₁ , and therefore, the voltage change of CH ₁ may be detected.

(Effects of the Invention) As is clear from the above description, according to the present invention, as described above, the voltage rise between the choke coil terminals that occurs when the load is disconnected is detected and the circuit is immediately cut off. Since the switching element is turned off, the switching element does not directly charge or discharge the capacitor, eliminating the conventional problems and increasing the reliability of the inverter device.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram for explaining one embodiment of the present invention, Figs. 2 and 3 are explanatory diagrams of voltage waveforms at various parts, and Fig. 4 is an emergency circuit diagram for explaining an embodiment of the present invention. FIG. 3 is an explanatory diagram when using a three-phase AC power supply device. R _I , S _I , T _I ... Three-phase commercial input power supply, B ... Storage battery, r, s, t ... AC output terminal, R, S, T ...
...Load connection terminal, C ₁₀ to C ₁₂ ... Spike voltage absorption capacitor, CH ₁ , CH ₂ ... Chiyoke coil,
Tr ₆ , Tr ₃ , Tr ₁₂ , Tr ₉ , Tr ₁₈ , Tr ₁₅ ... Switching transistor, O ... Oscillator, SH ₁ , SH ₂ ...
...shift register.

Claims (1)

[Claims] 1. A switching element connected between one end of the DC power supply and the AC output terminal, a switching element connected between the AC output terminal and the other end of the DC power supply, and a switching element connected between the AC output terminal and the other end of the DC power supply. In a protection circuit for an emergency AC power supply using an inverter having a capacitor for absorbing spike voltage and switching the switching element, a chiyoke coil is inserted into a direct current circuit, and the terminal voltage of the chiyoke coil is detected. A protection circuit for an emergency AC power supply, characterized in that the inverter is stopped when the terminal voltage exceeds a predetermined value.