JP2004040882A - Starter of induction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a starter for an induction machine whose characteristics do not change depending on temperature. <P>SOLUTION: A detection voltage at a detection coil D is stepped up by a transformer T. Photo MOS type FETMOS1 and MOS2 turn off a triac Tri based on the output from diodes D1 and D2 which have been delayed by a delay circuit 20, to stop a current to a start coil S. Since no mechanical switch is used, the start coil side can be energized only by a prescribed delay time independent of external temperature. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starting device that can be used for an induction machine including a main winding, a starting winding, and a detecting winding of an airtight motor (canned motor) for a submersible pump.
[0002]
[Prior art]
As an airtight motor for a submersible pump, an induction machine having a starting winding called a canned motor is widely used. The canned motor has a detection winding for detecting a magnetic flux of the main winding in addition to the main winding and the starting winding, detects a magnetic flux of the main winding via the detection winding, and starts after starting. Power supply to the winding is stopped. As a start relay for stopping the energization of the start winding, a type using no mechanical relay, such as a U.S. Pat. No. 4,292,555, is known in addition to a type using a mechanical relay. In this type, as shown in FIG. 4, a motor 190 including a main winding M, a starting winding S, and a detection winding D for detecting a magnetic flux of the main winding M is composed of a bimetal B and a triac Tri1. It is controlled by the starting relay 110. That is, the detection current in the detection winding D is applied to the bimetal B, and the application of the triac Tri1 is controlled by the bimetal B. Thus, after the motor is started, the current applied to the starting winding S is maintained until the bimetal B reverses. Electricity can be supplied.
[0003]
[Problems to be solved by the invention]
However, since the energizing time to the starting winding S is set by the bimetal B, the energizing time to the starting winding S changes depending on the ambient temperature. Here, since the canned motor is used as a submersible pump, there has been a problem that the energizing time to the starting winding S is not constant depending on the water temperature.
[0004]
Further, when the detection winding D is provided adjacent to the main winding M, efficiency such as copper loss is reduced. For this reason, it is desirable to reduce the number of turns of the detection winding D. However, if the number of turns is reduced, the voltage and current of the detection winding D become small, the operation becomes unstable, and even after the induction machine starts, In some cases, the energization of the starting winding continues.
[0005]
The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a starting device for an induction machine whose characteristics do not change with temperature.
[0006]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a starting device for an induction machine including a main winding, a starting winding, and a detecting winding, comprising:
A transformer for boosting a detection voltage at the detection winding;
A rectifier for rectifying the output from the transformer;
A delay circuit for conducting an output from the rectifier after a predetermined delay time;
A switch element for turning off a bidirectional current control element for turning on / off a current to the starting winding by an output from the rectifier delayed by the delay circuit.
[0007]
According to the first aspect, the detection voltage at the detection winding is boosted by a transformer, the boosted output is rectified by a rectifier, and the switch element outputs a current to the starting winding by the output from the rectifier delayed by the delay circuit. The bidirectional current control element to be turned on / off is turned off. Since a mechanical switch that opens and closes according to temperature is not used, it is possible to energize the starting winding for a predetermined delay time regardless of the external temperature. Further, since the detection voltage at the detection winding is boosted by the transformer, the current to the starting winding can be accurately controlled even when the number of turns of the detection winding is small and the output voltage is low.
[0008]
According to the second aspect, since the switch element is a normally-on type photo MOSFET, the number of turns of the detection winding is small and the current to the starting winding can be accurately controlled even if the output voltage is low.
[0009]
According to the third aspect, since the switch element is a photo MOSFET connected in series, the bidirectional current control element is turned off by turning off one of the photo MOSFETs even if the number of turns of the detection winding is small and the output voltage is low. Can be turned off, and the current to the starting winding can be reliably shut off.
[0010]
According to the fourth aspect, the rectifier is composed of a pair of diodes that rectify the current from the transformer half cycle at a time, and can perform full cycle rectification. The current can be controlled accurately.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a starting device for an induction machine according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an induction machine and a starting device according to an embodiment, and FIG. 2 is a circuit diagram of the starting device.
[0012]
As shown in FIG. 1, the induction machine 90 includes a main winding M, a starting winding S, and a detection winding D that detects a magnetic flux of the main winding M, and is a hermetic motor (canned motor) for a submersible pump. Motor). The induction machine 90 reduces the occurrence of copper loss by using one winding of the detection winding D. Here, the starting device 10 is connected to the a terminal, the b terminal, and the c terminal of the induction machine 90. After the starting of the induction machine 90, the triac Tri is energized for a predetermined period, so that the connection between the a terminal and the c terminal is established. The energization is enabled, and the energization to the starting winding S is performed. Here, the capacitor C1 and the resistor R1 connected in parallel with the triac Tri are so-called snubber circuits for eliminating a surge voltage or the like.
[0013]
As shown in FIG. 2, the starting device 10 includes a transformer T for boosting a detection voltage at the detection winding D, a pair of diodes D1 and D2 for rectifying an output from the transformer T, and outputs of the diodes D1 and D2. C2, a delay circuit 20 including a variable resistor R2, a resistor R3, a capacitor C3, and a transistor TR, and a photo MOSFET (MOS1) having an input connected to the output (emitter-base) of the transistor TR. ). The photo MOSFETs (MOS1) and (MOS2) are normally on (normally closed). As described above, the input side is connected in parallel with the output of the transistor TR, and the output side is connected to the terminal c-triac. It is connected in series between the gates of Tri.
[0014]
Here, the rectifier in the claims can correspond to the diodes D1 and D2, the bidirectional current control element can correspond to the triac Tri, and the switch element can correspond to the photo MOSFETs (MOS1) and (MOS2). The transformer T is set to, for example, 1:12, and boosts the detection winding voltage of the detection winding D to 12 times.
[0015]
Here, the operation of the starting device 10 will be described.
[At startup]
First, the operation at the time of startup will be described. When a voltage is applied to the induction machine 90, a current is applied to the gate of the triac Tri via the photo MOSFETs (MOS1) and (MOS2), the triac Tri turns on, and a current flows between the terminal a and the terminal c. The induction motor 90 is started by energizing the starting winding S.
[0016]
A detection current flows through the detection winding D at the same time when the induction machine 90 is started. The detected current is boosted by the transformer T and is subjected to double-wave rectification by the diodes D1 and D2. This rectified current is smoothed by the capacitor C2.
[0017]
The potential of the capacitor C2 is divided by the variable resistor R2 and the resistor R3 to charge the capacitor C3. Here, when the capacitor C3 is charged and reaches a predetermined potential, that is, when the base potential of the transistor TR becomes the predetermined potential, the transistor TR is turned on. That is, the charging time of the capacitor C3 becomes the delay time of the delay circuit 20.
[0018]
When the transistor TR conducts, a current other than the current shunted to the variable resistor R2 flows through the collector-emitter to the inputs of the photo MOSFETs (MOS1) and (MOS2). As a result, the output sides of the photo MOSFETs (MOS1) and (MOS2) are turned off, the triac Tri is turned off, the power supply to the starting winding S is stopped, and the induction machine 90 shifts to the normal operation.
[0019]
[Overload]
Subsequently, a case where the motor is locked due to overload will be described. Although the detection winding current is generated in the detection winding D in proportion to the rotation speed of the main winding of the motor, the detection winding current is not generated due to the lock of the induction machine 90. As a result, no current flows to the inputs of the photo MOSFETs (MOS1) and (MOS2), the photo MOSFETs (MOS1) and (MOS2) turn on, a current is applied to the gate of the triac Tri, and the triac Tri turns on. Then, a current flows through the starting winding S, and the motor is started again.
[0020]
When the overload state is resolved, the rotation speed of the motor increases, and at the same time, a detection winding current flows through the detection winding D. Since the energization of the starting winding S thereafter is the same as that at the time of the above-described starting, the description is omitted.
[0021]
In the starter of the induction machine according to the first embodiment, the detection voltage at the detection winding D is boosted by the transformer T, and the boosted output is rectified by the diodes D1 and D2, and the photo MOSFETs (MOS1) and (MOS2) The output from the diodes D1 and D2 delayed by the delay circuit 20 turns off the triac Tri and cuts off the current to the starting winding S. Since a mechanical switch that opens and closes according to temperature is not used, it is possible to energize the starting winding for a predetermined delay time regardless of the external temperature. In addition, since the detection voltage at the detection winding D is boosted by the transformer T, even if the number of turns of the detection winding D is small and the detection winding voltage is low, the current to the starting winding D can be accurately controlled. it can.
[0022]
In the first embodiment, normally-on type photo MOSFETs (MOS1) and (MOS2) are used as the switch elements for turning on and off the triac Tri. Therefore, even if the number of turns of the detection winding is small and the output voltage is low, that is, In addition, the current to the starting winding can be accurately controlled based on the low voltage input.
[0023]
In particular, since photo MOSFETs (MOS1) and (MOS2) connected in series are used as switch elements for turning on and off the triac Tri, even if the number of turns of the detection winding is small and the output voltage is low, the photo MOSFET (MOS1) and By turning off any of (MOS2), the triac Tri can be turned off, and the current to the starting winding can be reliably shut off. Further, since the photo MOSFETs (MOS1) and (MOS2) whose inputs and outputs are separated are used, malfunction due to noise can be prevented.
[0024]
Furthermore, as described above, in addition to the photo MOSFETs (MOS1) and (MOS2) whose input and output are separated, a transformer whose input and output are separated is used, so that malfunction due to noise can be completely prevented.
[0025]
In the starter of the induction machine according to the first embodiment, the rectifier is composed of a pair of diodes that rectify the current from the transformer half a cycle at a time. Even if the voltage is low, the current to the starting winding can be accurately controlled.
[0026]
Further, in the starter of the induction machine according to the first embodiment, since the operation is started from the generation of the current of the detection winding D after the start of the motor, no electric power is consumed during standby.
[0027]
Further, in the starting device of the induction machine according to the first embodiment, the delay time of the delay circuit 20 can be arbitrarily set by adjusting the variable resistor R2, thereby making it possible to optimize the energizing time to the starting winding S for the motor. It can be adjusted accurately so as to obtain a proper value.
[0028]
FIG. 3 shows a circuit configuration of a starting device for an induction machine according to a second embodiment. In the second embodiment, a Schmitt trigger circuit is used instead of the delay circuit 20 used in the circuit of the first embodiment. The Schmitt trigger circuit is a comparison circuit that outputs when an input voltage is equal to or higher than a certain value and does not output when the input voltage is equal to or lower than a certain value, and does not output an intermediate output. Since the detection winding outputs an output voltage proportional to the rotation speed of the motor, a certain rotation speed, that is, a certain voltage is determined as the threshold voltage of the Schmitt trigger circuit, as in the first embodiment. Control the start of the induction machine.
[0029]
【The invention's effect】
As described above, according to the present invention, the voltage detected by the detection winding is boosted by the transformer, the boosted output is rectified by the rectifier, and the switch element is activated by the output from the rectifier delayed by the delay circuit. Turn off the bidirectional current control element that turns on and off the current to the line. Since a mechanical switch that opens and closes according to temperature is not used, it is possible to energize the starting winding for a predetermined delay time regardless of the external temperature. Further, since the voltage detected by the detection winding is boosted by the transformer, the current to the starting winding can be accurately controlled even if the number of turns of the detection winding is small and the output voltage is low.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an induction machine and a starting device according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram of the starting device according to the first embodiment.
FIG. 3 is a circuit diagram of a starting device according to a second embodiment.
FIG. 4 is a block diagram showing an induction machine and a starting device according to the related art.
[Explanation of symbols]
Reference Signs List 10 starting device 20 delay circuit 90 induction machine M main winding S starting winding D detection winding T transformer D1, D2 diodes C1, C2, C3 capacitors R1, R3, R4, R5, R6, R7, R8, R9 resistor R2 Variable resistors TR, TR1, TR2, TR3, TR4 Transistor Tri Triac MOS1, MOS2 Photo MOSFET

Claims (4)

A starting device for an induction machine comprising a main winding, a starting winding, and a sensing winding, wherein:
A transformer for boosting a detection voltage at the detection winding;
A rectifier for rectifying the output from the transformer;
A delay circuit for conducting an output from the rectifier after a predetermined delay time;
A switching element for turning off a bidirectional current control element for turning on and off a current to the starting winding by an output from the rectifier delayed by the delay circuit. . 2. The starting device for an induction machine according to claim 1, wherein the switch element is a normally-on type photo MOSFET. 2. The starting device for an induction machine according to claim 1, wherein the switch element is configured by connecting a plurality of MOSFETs in series. 4. The starter for an induction machine according to claim 1, wherein the rectifier includes a pair of diodes that rectify the current from the transformer for each half cycle. 5.

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