JP3566443B2 - Inverter overvoltage protection device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an invar overvoltage protection device for supplying regenerative electric power to a resistor to consume the regenerative electric power and to protect the inverter from being overvoltage by the regenerative electric power.
[0002]
[Prior art]
This will be described with reference to FIGS.
FIG. 4 shows an inverter device to which a first prior art inverter overvoltage protection device is applied, 10 is a PWM inverter, 20 is an input power supply, 30 is an induction motor (hereinafter referred to as IM), and 40 is an overvoltage protection device. Reference numeral 50 denotes a power switch.
In the PWM inverter 10, reference numeral 11 denotes a DC smoothing unit that obtains the three-phase AC input power supply 20 from the power switch 50 and smoothes the DC power, and 12 denotes a DC charging unit that charges the power smoothed by the DC smoothing unit 11. , 13 is an inverter unit for supplying arbitrary three-phase AC power to the IM 30, and 14 is a control circuit for controlling the inverter unit 13.
In the overvoltage protection device 40, 41 is a resistor that consumes regenerative power, 42 is a voltage detector that detects the voltage of the DC charging unit 12, and 43 is a value corresponding to a preset allowable upper limit value of the DC charging unit 12. , A comparator 44 for comparing the set reference value 43 with the output of the voltage detector 42, a switching element 45 driven by the comparator 44, and a cooling fan motor (hereinafter referred to as FM) 46. is there.
As is well known, the series circuit of the resistor 41 and the switching element 45 connected to the DC charging unit 12 supplies the DC charging unit power to the resistor 41 when the detected voltage value of the DC charging unit 12 is larger than the reference value. It is controlled so as to be energized.
[0003]
Here, the overvoltage protection device 40 is provided with an FM 46 supplied with power from outside the PWM inverter 10, and the FM 46 is configured to cool the resistor 41 and the switching element 45.
This is to prevent a fire due to overheating of the resistor 41 and a damage due to overheating of the switching element 45 when the regenerative power is consumed.
The FM 46 is supplied with power at the same time as the input power 20 is supplied to the PWM inverter 10 through the power switch 50. That is, the operation is started by the power input of the PWM inverter, and the operation is stopped at the same time as the power supply to the PWM inverter is cut off.
[0004]
FIG. 5 shows a second conventional example in a manner similar to FIG. 4, wherein reference numeral 15 denotes an operation signal switch, and reference numeral 60 denotes a power switch.
In FIG. 5, a power supply on / off switch 60 is provided on the power supply input side of the FM 46 of the overvoltage protection device 40, and the operation of the power supply on / off switch 60 is controlled by the PWM inverter input to the control circuit 14 of the PWM inverter 10. Is configured to operate in conjunction with the operation signal switch 15.
That is, power is supplied to the FM 46 during a period in which the PWM inverter is operated, and the FM 46 is also stopped while the PWM inverter 10 is stopped. Therefore, the operation period of the FM 46 is shorter than that of the first conventional example.
[0005]
[Problems to be solved by the invention]
As described above, in the prior art example, the operation period of the FM in the inverter overvoltage protection device is a period in which power is supplied to the PWM inverter or a period in which the PWM inverter is operated.
However, the life of the FM is shorter than the life of the PWM inverter and other devices of the overvoltage protection device, and it is necessary to replace the FM before reaching the product life.
However, the period during which the overvoltage protection device is actually operated may be only the period during which the regenerative power generated during the period in which the IM is decelerated or stopped or the period in which the IM is turned by the load machine is supplied to the resistor by the switching element. .
As described above, according to the conventional method, there are many useless periods during the operation of the FM, which is a major factor in shortening the life of the FM.
Further, when the operation period of the FM is performed by using the on / off switch, a signal for controlling the on / off switch is connected to synchronize the operation signal of the PWM inverter with an operation signal of the PWM inverter, and a connection from an external power supply for supplying power to the FM. There's a problem.
[0006]
An object of the present invention is to provide an inverter overvoltage protection device in which the operation period of the FM of the inverter overvoltage protection device is synchronized with the operation period of the overvoltage protection device and the life of the FM is extended. is there.
[0007]
[Means for Solving the Problems]
The present invention has been made in view of the above points, and has the following configuration.
First, a resistor connected to the DC charging unit of the PWM inverter, a comparator for comparing the output of the voltage detector for detecting the voltage of the DC charging unit with a preset reference value, and a comparator output are obtained. A switching element for supplying regenerative electric power generated when the IM is decelerated or stopped by a load machine or the like to the resistor, and an FM for cooling the resistor and the switching element. A power on / off switch for supplying power to the power supply and an operation circuit for receiving the output of the comparator as an input, and operating the power on / off switch in accordance with the output of the comparator.
[0008]
Further, the operation circuit provides a first command output for supplying power as soon as the switching element operates to drive the resistor to consume the regenerative power, or stops the driving of the switching element and outputs the regenerative power to the resistor. When operating in a direction that does not consume power, a path switch that switches to the input side of a delay calculator that provides a second command output that shuts off power supply with a delay due to the thermal time constant of the switching element and the resistor is provided. It was made.
Furthermore, a DC / DC converter having an input of a DC charging unit as an input is provided on the input side of the power on / off switch, and power is supplied to the FM.
[0009]
With such a solution, the following effects can be obtained. That is,
At the timing when the output of the comparator drives the switching element to cause the resistor to consume regenerative power, the power supply on / off switch provided in the power supply unit of the FM is operated to the power supply side to start the operation of the FM. I do. Here, the operation of the power on / off switch is such that when the output of the comparator drives the switching element to start consuming regenerative power, it immediately operates on the side that supplies power to the FM. Is configured to operate on the side that stops the power supply of the FM, so that it is possible to eliminate unnecessary operation of the FM.
When the output of the comparator operates in a direction to stop the driving of the switching element, that is, at the time when the regenerative power is not consumed, the power should be cut off with a delay considering a thermal time constant of the switching element and the resistor. Thereby, the heat stored inside the switching element and the resistor can be cooled.
Furthermore, by preparing the power supply of FM in the overvoltage protection device, power is not supplied from the outside and the power for FM is created, so the load resistance is equivalently attached to the DC charging part. Therefore, when the DC charging unit voltage is increased by the regenerative power, the FM can consume a part of the regenerative power.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Specifically, particularly in the configuration of the inverter overvoltage protection device, an operation circuit having a path changeover switch and a delay calculator using a drive output to the switching element as an input, a power supply open / close switch operated by the operation circuit output, And a DC / DC converter that receives the output of the DC charging unit as input and supplies power to the FM via a power switch.
Further, the present invention will be described in detail with reference to the drawings.
[0011]
【Example】
FIG. 1 shows an embodiment of the present invention in a manner similar to FIGS. 4 and 5, and reference numeral 40 'denotes an overvoltage protection device.
That is, the overvoltage protection device 40 'is provided. In particular, the overvoltage protection device 40' includes a power line and a power on / off switch for the FM 46 of the overvoltage protection device 40 'as shown in FIGS. It has been removed.
In the overvoltage protection device 40 ', the resistor 41, the voltage detector 42, the setting reference value 43, the comparator 44, the switching element 45, and the FM 46 are used in the same manner as in the prior art. The device 40 'is provided with an operation circuit 47, a power switch 48 and a DC / DC converter 49.
[0012]
Further, a description will be given with reference to FIGS.
FIG. 2 shows an example of the operation circuit 47 of FIG. 1, 471 is a path changeover switch, 472 is a delay calculator, DR is a command input, and DR1 and DR2 are command outputs.
FIG. 3 shows an operation state of the FM 46, where Ts is a switching cycle and Th is a thermal time constant.
[0013]
Now, in the overvoltage protection device 40 ', the switching element 45 obtains the output of the comparator 44, and detects the time when the regenerative power is supplied to the resistor 41 and the time when the power supply is stopped.
The operation circuit 47 generates a command output DR1 from the command input DR from the output of the comparator 44 through the path switch 471 at the time of energization. Therefore, the power supply on / off switch 48 provided in the FM46 power input unit is operated. An operation is performed in a direction in which power is supplied to the FM 46, and the FM 46 starts operating.
When the supply of the regenerative power to the resistor 41 is stopped by the comparator 44 and the switching element 45, the power supply on / off switch 48 is not operated so as to stop the power supply to the FM 46 immediately. And a delay calculator 472 for calculating a delay time corresponding to the thermal time constant of the switching element 45 is used.
That is, the command output DR2 is generated by the path switch 471 and the delay calculator 472, and the operation of the power switch 48 is delayed. Therefore, the operation of the FM 46 is continued until the heat inside the resistor 41 and the switching element 45 is cooled. This is as shown in FIG.
[0014]
In FIG. 3, the thermal time constant Th of the resistor 41 and the switching element 45 is usually sufficiently long with respect to the switching period Ts in which the switching element 45 operates according to the output of the comparator 5, that is, the command input DR. The FM 46 does not stop during the normal operation, and the FM 46 stops when the period during which the output of the comparator 41 is completely stopped exceeds the thermal time constant Th.
Therefore, even when the electric motor in which the regenerative operation is intermittent during the period of the thermal time constant Th is intermittently operated, the overvoltage protection device can be efficiently cooled.
Further, a DC / DC converter 49 is provided in the overvoltage protection device 1 and can supply power from the DC charging unit 12 of the PWM inverter 10 to generate power for the FM 46 and supply the power.
[0015]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to extend the life of the FM for cooling the inverter device overvoltage protection device, thereby improving the reliability of the overvoltage protection device and reducing maintenance for FM replacement. A device with a remarkable practical effect can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing one embodiment of the present invention.
FIG. 2 is a diagram showing an example of an operation circuit of FIG. 1;
FIG. 3 is a diagram showing an operation state of the cooling fan motor according to the present invention.
FIG. 4 is a block diagram showing a first conventional example.
FIG. 5 is a block diagram showing a second conventional example.
[Explanation of symbols]
Reference Signs List 10 PWM inverter 11 DC smoothing unit 12 DC charging unit 13 Inverter unit 14 Control circuit 15 Operation signal switch 20 Input power supply 30 Induction motor (IM)
Reference Signs List 40 Overvoltage protection device 40 'Overvoltage protection device 41 Resistor 42 Voltage detector 43 Setting reference value 44 Comparator 45 Switching element 46 Cooling fan motor (FM)
47 Operation circuit 471 Path switch 472 Delay calculator 48 Power switch 49 DC / DC converter 50 Power switch 60 Power switch DR Command input DR1 Command output DR2 Command output Ts Switching cycle Th Thermal time constant

Claims (2)

A resistor connected to a DC charging unit of the PWM inverter, a comparator for comparing an output of a voltage detector for detecting a voltage of the DC charging unit with a preset reference value, and obtaining an output of the comparator. A switching element that supplies regenerative power generated when the induction motor is decelerated or stopped or is rotated by a load machine or the like to the resistor, and a cooling fan motor that cools the resistor and the switching element. In an inverter overvoltage protection device comprising:
A power supply on / off switch for supplying power to the cooling fan motor and an operation circuit having a comparator output as an input, and operating the power supply on / off switch in accordance with the comparator output,
The manipulation circuit, said to give an immediate first instruction output power supply when operating in a direction to consume regenerative electric power switching element to the resistor is driven, and the regenerative power to the resistor by stopping the driving of the switching element When operating in a direction that does not consume power, a path switch that switches to the input side of a delay calculator that provides a second command output that shuts off power supply with a delay due to the thermal time constant of the switching element and the resistor is provided. An inverter overvoltage protection device, characterized in that: 2. The inverter overvoltage protection device according to claim 1, further comprising: a DC / DC converter that receives the output of the DC charging unit as an input, and supplies power to the cooling fan motor on an input side of the power switch.

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