Abstract:
A phase sequence detecting apparatus for a three-phase alternating current (AC) power includes a signal converting module and a phase sequence indicating module comprising plural indicating lights. The phase sequence detecting apparatus further includes a control module. The signal converting module is configured to receive three phase power signals output from the three-phase AC power, configured to convert the three phase power signals and send the converted signals to the control module. The control module controls power-on sequence of the indicating lights according to signals output from the signal converting module.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a power supply detecting circuit capable of detecting a phase sequence of a polyphase power source. 
         [0003]    2. Description of Related Art 
         [0004]    Three-phase power sources are common polyphase power sources used by grids worldwide to transfer power. Three-phase power is also used to power large motors and other large loads. A three-phase system is generally more economical because it uses less conductor material to transmit electric power than equivalent single-phase or two-phase systems at the same voltage. A typical three-phase power source includes three output terminals which reach their instantaneous peak values at different times. Taking one power rail as the reference, the other two power rails are delayed in time by one-third and two-thirds of one cycle of the electric current. The three-phase power source has the only phase sequence and the power rails of the three-phase power source should be correctly connects to power input terminals of the three-phase motors or the three-phase loads. However, the phase sequence of the three-phase power supply is sometimes unknown to users, which causes the motors or loads are connected to the power source incorrectly. 
         [0005]    Therefore, what is needed, is a power supply detecting circuit capable of detecting a phase sequence of the polyphase power supply. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0007]      FIG. 1  is a block diagram of a power supply detecting circuit according to an embodiment. 
           [0008]      FIG. 2  is a detailed circuit of the power supply detecting circuit of  FIG. 1 . 
           [0009]      FIG. 3  illustrates waveforms of output powers rails of a three-phase power source. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    The disclosure is illustrated by way of example and not by way of limitation. In the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
         [0011]    In general, the word “module,” as used herein, refers to logic embodied in hardware or firmware, or to a collection of software instructions, written in a programming language, such as, for example, Java, C, or assembly. One or more software instructions in the modules may be embedded in firmware, such as an EPROM. It will be appreciated that modules may comprise connected logic units, such as gates and flip-flops, and may comprise programmable units, such as programmable gate arrays or processors. The modules described herein may be implemented as either software and/or hardware modules and may be stored in any type of computer-readable medium or other computer storage device. 
         [0012]    Referring to  FIG. 1 , an embodiment of power supply detecting circuit includes a converting module  10 , a control module  20 , and a phase sequence indicating module  30 . In one embodiment, the power supply detecting circuit is configured to detect a phase order of a three-phase alternative current (AC) power source which has three live wires and a neutral wire. The three live wires output three AC power rails which reach their instantaneous peak values at different times. Taking one power rail as the reference, the other two power rails are delayed in time by one-third and two-thirds of one cycle of the electric current. 
         [0013]    Referring to  FIGS. 2 and 3 , the converting module  10  includes a first signal converting circuit  11 , a second signal converting circuit  12 , and a third signal converting circuit  13 . 
         [0014]    The first signal converting circuit  11  includes a first resistor R 1 , a second resistor R 2 , a third resistor R 3 , a first optical coupler U 1 , and a first capacitor C 1 . A first terminal of the first resistor R 1  is connected to a first live wire X 1  of the three-phase AC power source. A second terminal of the first resistor R 1  is connected to the first optical coupler U 1 . The first optical coupler U 1  includes a first light emitting diode (LED) D 1  and a first light sensitive transistor Q 1 . An anode of the first LED D 1  is connected to the first resistor R 1 . A cathode of the first LED D 1  is connected to the neutral wire N of the three-phase AC power source. The second resistor R 2  and the first LED D 1  are connected in parallel. A collector of the first light sensitive transistor Q 1  is coupled to a +5V direct current (DC) power via the third transistor R 3 . An emitter of the first light sensitive transistor Q 1  is connected to ground. The first capacitor C 1  is connected between the collector and the emitter of the first light sensitive transistor Q 1 . When a voltage output from the first live wire X 1  exceeds a predetermined threshold value U 0  (see  FIG. 3 ), the first LED D 1  is lit. The first light sensitive transistor Q 1  is rendered conductive. The first signal converting circuit  11  outputs a low level voltage Y 1  (Y 1 =0V) to the control module  20 . When the voltage output from the first live wire X 1  is less than the predetermined threshold value U 0 , the first LED D 1  is powered off. The first light sensitive transistor Q 1  is rendered non-conductive. The first signal converting circuit  11  outputs a high level voltage Y 1  (Y 1 =+4.8V) to the control module  20 . In one embodiment, a resistance of the first resistor R 1  is much greater than that of the second resistor R 2 . Thus, a voltage drop across the first resistor R 1  is much greater than that across the second resistor R 2 , so that the first resistor R 1  can prevent overvoltage damage to the first LED D 1 . 
         [0015]    The second signal converting circuit  12  includes a fourth resistor R 4 , a fifth resistor R 5 , a sixth resistor R 6 , a second optical coupler U 2 , and a second capacitor C 2 . A first terminal of the fourth resistor R 4  is connected to a second live wire X 2  of the three-phase AC power source. A second terminal of the fourth resistor R 4  is connected to the second optical coupler U 2 . The second optical coupler U 2  includes a second LED D 2  and a second light sensitive transistor Q 2 . An anode of the second LED D 2  is connected to the fourth resistor R 4 . A cathode of the second LED D 2  is connected to the neutral wire N of the three-phase AC power source. The fifth resistor R 5  and the second LED D 2  are connected in parallel. A collector of the second light sensitive transistor Q 2  is coupled to the +5V DC power via the sixth transistor R 6 . An emitter of the second light sensitive transistor Q 2  is connected to ground. When a voltage output from the second live wire X 2  exceeds the predetermined threshold value U 0  (see  FIG. 3 ), the second LED D 2  is lit. The second light sensitive transistor Q 2  is rendered conductive. The second signal converting circuit  12  outputs a low level voltage Y 2  (Y 2 =0V) to the control module  20 . When the voltage output from the second live wire X 2  is less than the predetermined threshold value U 0 , the second LED D 2  is powered off. The second light sensitive transistor Q 2  is rendered non-conductive. The second signal converting circuit  12  outputs a high level voltage Y 2  (Y 2 =+4.8V) to the control module  20 . A resistance of the fourth resistor R 4  is much greater than that of the fifth resistor R 5 . Thus, the fourth resistor R 4  can prevent overvoltage damage to the second LED D 2 . 
         [0016]    The third signal converting circuit  13  includes a seventh resistor R 7 , an eighth resistor R 8 , a ninth resistor R 9 , a third optical coupler U 3 , and a third capacitor C 3 . A first terminal of the seventh resistor R 7  is connected to a third live wire X 3  of the three-phase AC power source. A second terminal of the seventh resistor R 7  is connected to the third optical coupler U 3 . The third optical coupler U 3  includes a third LED D 3  and a third light sensitive transistor Q 3 . An anode of the third LED D 3  is connected to the seventh resistor R 7 . A cathode of the third LED D 3  is connected to the neutral wire N. The eighth resistor R 8  and the third LED D 3  are connected in parallel. A collector of the third light sensitive transistor Q 3  is coupled to the +5V DC power via the ninth transistor R 9 . An emitter of the third light sensitive transistor Q 3  is connected to ground. When a voltage output from the third live wire X 3  exceeds the predetermined threshold value U 0  (see  FIG. 3 ), the third LED D 3  is lit. The third light sensitive transistor Q 3  is rendered conductive. The third signal converting circuit  13  outputs a low level voltage Y 3  (Y 3 =0V) to the control module  20 . When the voltage output from the third live wire X 3  is less than the predetermined threshold value U 0 , the third LED D 3  is powered off. The third light sensitive transistor Q 3  is rendered non-conductive. The third signal converting circuit  13  outputs a high level voltage Y 3  (Y 3 =+4.8V) to the control module  20 . A resistance of the seventh resistor R 7  is much greater than that of the eighth resistor R 8 . Thus, the seventh resistor R 7  can prevent overvoltage damage to the second LED D 2 . 
         [0017]    In one embodiment, the first signal converting circuit  11 , the second signal converting circuit  12 , and the third signal converting circuit  13  have the same components and circuit connections. 
         [0018]    The control module  20  includes a single chip microcontroller  22  with pins PA 0 -PA 7  (I/O pins)           PB 0 -PB 7  (I/O pins)           PC 0 -PC 7  (I/O pins)           PD 0 -PD 7  (I/O pins)           RESET (reset pin)           VCC (power pin)           GND (ground pin). The PB 2  pin is connected to the first signal converting circuit  11  for receiving the output signal Y 1 . The PD 2  pin is connected to the second signal converting circuit  12  for receiving the output signal Y 2 . The PD 3  pin is connected to the third signal converting circuit  13  for receiving the output signal Y 3 . A reset key K 1  is connected to the RESET pin of the single chip microcontroller  22 . The VCC pin is coupled to the +5V DC power. The GND pin is connected to ground. 
         [0019]    The phase sequence indicating module  30  includes a first indicator LED 1 , a second indicator LED 2 , and a third indicator LED 3 . The indicators are different colored LED lamps. An anode of the first indicator LED 1  is connected to the PC 0  pin of the single chip microcontroller  22 . A cathode of the first indicator LED 1  is connected to ground via a tenth resistor R 10 . An anode of the second indicator LED 2  is connected to the PC 1  pin of the single chip microcontroller  22 . A cathode of the second indicator LED 2  is connected to ground via the tenth resistor R 10 . An anode of the third indicator LED 3  is connected to the PC 2  pin of the single chip microcontroller  22 . A cathode of the third indicator LED 3  is connected to ground via the tenth resistor R 10 . 
         [0020]    To detect the phase sequence of the three-phase AC power source, the reset key K 1  is pressed, and the single chip microcontroller  22  starts to work. Then, the three-phase AC power source is switched on, and the live wires X 1 , X 2 , and X 3  start to output AC voltages. If the phase sequence of the three-phase AC power source is X 1 →X 2 →X 3 , the X 1  power rail firstly reaches the predetermined value U 0 . The first optical coupler U 1  is switched on. The output signal Y 1  from the first signal converting circuit  11  is at low level and sent to the PB 2  pin of the single chip microcontroller  22 . The PC 0  pin of the single chip microcontroller  22  outputs a high level voltage to the first indicator LED 1 . The first indicator LED 1  is lit firstly, while the second indicator LED 2  and the third indicator LED 3  are still powered off. After one third cycle, the X 2  power rail reaches the predetermined value U 0 . The second optical coupler U 2  is switched on. The output signal Y 2  from the second signal converting circuit  12  is at low level and sent to the PD 2  pin of the single chip microcontroller  22 . The PC 1  pin of the single chip microcontroller  22  outputs a high level voltage to the second indicator LED 2 . The second indicator LED 2  is lit after one third cycle while the first indicator LED 1  is still lit. After two third cycles, the X 3  power rail reaches the predetermined value U 0 . The third optical coupler U 3  is switched on. The output signal Y 3  from the third signal converting circuit  13  is at low level and sent to the PD 3  pin of the single chip microcontroller  22 . The PC 2  pin of the single chip microcontroller  22  outputs a high level voltage to the third indicator LED 3 . The third indicator LED 3  is lit after another one third cycle. Thus the first indicator LED 1 , the second indicator LED 2 , and the third indicator LED 3  are lit one by one in sequence; LED 1 →LED 2 →LED 3 . Then the phase sequence of the three-phase AC power source is X 1 →X 2 →X 3 . If the first indicator LED 1 , the second indicator LED 2 , and the third indicator LED 3  are lit one by one in a different sequence; L 2 →L 3 →L 1 , then the phase sequence of the three-phase AC power source is X 2 →X 3 →X 1 . If the first indicator L 1 , the second indicator L 2 , and the third indicator L 3  are lit one by one in yet another sequence; LED 3 →LED 2 →LED 1 , the phase sequence of the three-phase AC power source is X 3 →X 2 →X 1 . The power on sequence of the first indicator LED 1 , the second indicator LED 2 , and the third indicators LED 3  indicate the phase sequence of the three-phase AC power source being tested. 
         [0021]    In one embodiment, the AC power source to be tested is a two phase, or four or more phase AC power source, and circuits similar to the above described detecting circuit can be utilized to detect the phase sequence of the polyphase AC power source. 
         [0022]    While the present disclosure has been illustrated by the description of preferred embodiments thereof, and while the preferred embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications within the spirit and scope of the present disclosure will readily appear to those skilled in the art. Therefore, the present disclosure is not limited to the specific details and illustrative examples shown and described.