THAT INA MI CORA UNA IMA US009759756B2

(12) United States Patent ( 10) Patent No.: US 9, 759,756 B2

Ma et al. (45 ) Date of Patent: Sep . 12, 2017
( 54 ) CIRCUIT AND METHOD FOR (56 ) References Cited
THREE - PHASE DETECTION , AND U .S . PATENT DOCUMENTS
COMPRESSOR
2016 /0356824 A1 * 12/2016 Wu ...................... GOIR 19 /22
(71) Applicant: Danfoss (Tianjin) Ltd., Tianjin (CN)
(72 ) Inventors : Zhenqiang Ma, Tianjin (CN ); FOREIGN PATENT DOCUMENTS
Jingyuan Li, Tianjin ( CN ); Huapeng CN 2708552 Y 7 /2005
Zeng, Tianjin (CN ) CN 1866659 A 11 /2006
CN 101799520 A 8 / 2010
CN 101871982 A 10 / 2010
(73 ) Assignee : Danfoss ( Tianjin ) Ltd ., Tianjin (CN ) CN 203444023 U 2 / 2014
CN 204101643 U 1 / 2015
( * ) Notice : Subject to any disclaimer, the term of this CN 104360173 A 2 / 2015
patent is extended or adjusted under 35 * cited by examiner
U . S .C . 154 (b ) by 0 days .
(21) Appl. No.: 14/967,534 Primary Examiner — Karen Masih
(74 ) Attorney, Agent, or Firm - McCormick , Paulding &
Huber LLP
(22) Filed : Dec. 14 , 2015
(65) Prior Publication Data (57) ABSTRACT
A circuit for three - phase detection , a method for three -phase
US 2016 /0169952 A1 Jun . 16 , 2016 detection and a compressor are provided . The circuit for
three - phase detection includes a first optical coupler and a
(30) Foreign Application Priority Data second optical coupler. A first input end and a second input
end of the first optical coupler are respectively connected to
Dec. 15 , 2014 (CN ).......................... 2014 1 0775649 a first phase wire and a third phase wire of a power supply
assembly, and a first output end of the first optical coupler
(51) Int. CI. provides a first output signal. A first input end and a second
GOIR 31 /02 ( 2006 .01) input end of the second optical coupler are respectively
GOIR 29 / 18 ( 2006 .01) connected to a second phase wire and the third phase wire
HO2P 29/024 (2016 . 01) of the power supply assembly , and a first output end of the
(52) U .S . CI. second optical coupler provides a second output signal. The
CPC .......... GOIR 29 / 18 ( 2013 .01 ); H02P 29 /0241 first output signal and the second output signal are used to
( 2016 .02) indicate a phase state of a three -phase alternating current of
(58 ) Field of Classification Search the power supply assembly .
??? .......... GO2B 6 /26 ; HO2P 29 /0241
See application file for complete search history . 14 Claims, 5 Drawing Sheets

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 US 9 ,759,756 B2
CIRCUIT AND METHOD FOR According to another aspect of the present invention , a
THREE - PHASE DETECTION , AND method for three -phase detection is provided . The method
COMPRESSOR includes : receiving , by a first optical coupler, a signal of a
first phase wire and a signal of a third phase wire that are
CROSS REFERENCE TO RELATED 5 from a power supply assembly , and outputting a first output
APPLICATIONS signal according to the signal of the first phase wire and the
signal of the third phase wire ; receiving , by a second optical
Applicant hereby claims foreign priority benefits under coupler, a signal of a second phase wire and the signal of the
third phase wire of the power supply assembly , and provid
U . S . C . $ 119 from Chinese Patent Application Serial No . ing a second output signal according to the signal of the
CN201410775649 . 0 filed on Dec . 15 , 2014 , the contents of 1 second phase wire and the signal of the third phase wire ; and
which are incorporated by reference herein . detecting, based on the first output signal and the second
output signal, a phase state of a three - phase alternating
FIELD OF THE INVENTION current of the power supply assembly .
The present invention relates to the field of circuit tech BRIEF DESCRIPTION OF THE DRAWINGS
nologies , and in particular , to a circuit for three-phase The present invention will be described in more detail
detection , a method for three -phase detection , and a com with reference to the accompanying drawings . The accom
pressor to which the circuit for three - phase detection and/ or panying drawings are intended to describe rather than limit
the method for three -phase detection are /is applied . 20 the present invention . The accompanying drawings are not
drawn to scale , and shapes thereof are also examples , rather
BACKGROUND than exactly correspond to shapes of actual products.
FIG . 1 shows a circuit for three -phase detection according
Three -phase alternating current is widely applied in vari to an embodiment of the present invention ;
ous fields. Generally, a three -phase alternating current sys - 25 FIG . 2A shows a waveform diagram of a three -phase
tem transmits electricity by using three live lines whose alternating current in a normal phase state ;
phases differ by 120 degrees, where a neutral wire is FIG . 2B shows, according to an embodiment of the
optionally included . Phases of the three live lines may be present invention , waveform diagrams of a first output
separately referred to as a U phase , a V phase , and a W signal and a second output signal of the circuit for three
phase . The phases of a three - phase alternating current may 30 phase detection when the three -phase alternating current is
change due to a change of a working environment and/ or a in a normal phase state ;
malfunction in a circuit, for example , phase loss or phase FIG . 3A shows, according to the embodiment of the
reversal, thereby causing damage to electrical equipment present invention , waveform diagrams of the first output
Therefore , it is necessary to detect the phases of the three signal and the second output signal of the circuit for three
phase alternating current, in order to ensure that the elec - 35 phase detection when phase loss occurs in a first phase wire
trical equipment works in a normal power supply condition of the three -phase alternating current;
However, there are too many components in most con - FIG . 3B shows, according to an embodiment of the
ventional solutions for three - phase circuit detection , and present invention , waveform diagrams of the first output
therefore , the conventional solutions have complex struc - signal and the second output signal of the circuit for three
tures, and thus have high costs while poor reliability. 40 phase detection when phase loss occurs in a second phase
wire of the three- phase alternating current;
SUMMARY FIG . 3C shows, according to an embodiment of the
present invention , waveform diagrams of the first output
In view of the foregoing, an aspect of the present inven - signal and the second output signal of the circuit for three
tion provides a circuit for three - phase detection . The circuit 45 phase detection when phase loss occurs in a third phase wire
for three - phase detection includes a first optical coupler and of the three - phase alternating current;
a second optical coupler, where a first input end and a second FIG . 3D shows, according to an embodiment of the
input end of the first optical coupler are respectively con present invention , waveform diagrams of the first output
nected to a first phase wire and a third phase wire of a power signal and the second output signal of the circuit for three
supply assembly, and a first output end of the first optical 50 phase detection when phase loss occurs in at least two
coupler provides a first output signal; and a first input end phases of wires of the three -phase alternating current;
and a second input end of the second optical coupler are FIG . 4 shows , according to the embodiment of the present
respectively connected to a second phase wire and the third invention , waveform diagrams of the first output signal and
phase wire of the power supply assembly , and a first output the second output signal of the circuit for three-phase
end of the second optical coupler provides a second output 55 detection when phase reversal occurs in two phases of wires
signal, where waveforms of the first output signal and the of the three -phase alternating current;
second output signal are used to indicate a phase state of a FIG . 5 shows a compressor including a circuit for three
three -phase alternating current of the power supply assem - phase detection according to an embodiment of the present
bly . invention ; and
Another aspect of the present invention provides a com - 60 FIG . 6 shows a flowchart of detecting phases of a three
pressor. The compressor includes : a compression member, a phase alternating current according to an embodiment of the
motor, and the circuit for three -phase detection described present invention .
above , where the motor is configured to drive the compres
sion member to compress a medium that enters the com DETAILED DESCRIPTION
pressor; and the circuit for three -phase detection is con - 65
nected to the motor , and is configured to detect a phase state Embodiments of the present invention are described
of the motor. below with reference to the accompanying drawings. It
 US 9 ,759,756 B2
should be understood that, the following implementation TABLE 1 -continued
manners are examples but not exhaustive , and are merely
used to describe the principle of the present invention , rather Number The phase state The states of OUT1 and OUT2
than to limit the scope of the present invention . Phase loss occurs in the U Both OUT1 and OUT2 are at
In a conventional solution of three -phase detection , phase 5 phase wire and the W
phase wire
high electrical levels
loss or phase reversal is detected by using three or four Phase loss occurs in the V Both OUT1 and OUT2 are at
a

optical couplers, a corresponding operational amplifier cir phase wire and the W high electrical levels
cuit and a microcontroller. Too many components are phase wire
Phase loss occurs in the U Both OUT1 and OUT2 are at
needed , a circuit structure is complex , costs are high , and phase wire , the V phase high electrical levels
reliability is poor. wire and the W phase
FIG . 1 shows a circuit for three -phase detection 100 wire
according to an embodiment of the present invention . The
circuit for three -phase detection 100 is used to detect phases
of a three -phase alternating current, where transmission is As shown in Table 1, when the first output signal OUT1
performed in the three -phase alternating current by using a 15 is at a high electrical level and the second output signal
first phase wire, a second phase wire, and a third phase wire . OUT2 is a square wave signal, it indicates that phase loss
It should be noted that, “ first” . “ second ” . “ third ” and the like occurs in the first phase wire U ; when the second output
that are used in this text are merely used to differentiate signal OUT2 is at a high electrical level and the first output
different objects, which does not means that there is any signal OUT1 is a square wave signal, it indicates that phase
specific sequential relationship between these objects . 20 loss occurs in the second phase wire V ; when the first output
As shown in FIG . 1 , the circuit for three - phase detection signal OUT1 and the second output signal OUT2 are square
100 in this embodiment of the present invention includes a wave signals with the samephase , it indicates that phase loss
first optical coupler 102 and a second optical coupler 104 . A occurs in the third phase wire W ; and when both the first
first input end 102 - 1 and a second input end 102- 2 of the first output signal and the second output signal are at high
optical coupler 102 are respectively connected to a first 25 electrical levels, it indicates thatphase loss occurs in at least
phase wire U and a third phase wire W . A first output end two wires of the first, second , and third phase wires .
102- 3 of the first optical coupler provides a first output FIG . 3A shows waveform diagrams of the first output
signal OUT1. A first input end 104 - 1 and a second input end signal OUT1 and the second output signal OUT2 when
104 - 2 of the second optical coupler 104 are respectively phase loss occurs in the first phase wire U . As shown in FIG .
connected to a second phase wire V and the third phase wire 30 3A , when phase loss occurs in the first phase wire U , the first
W . A first output end 104 - 3 of the second optical coupler 104 output signal OUT1 maintains a high electrical level, and the
provides a second output signal OUT2 . Waveforms of the second output signal OUT2 is a square wave signal.
first output signal OUT1 and the second output signal OUT2 FIG . 3B shows waveform diagrams of the first output
are used to indicate a phase state , for example , phase loss signal OUT1 and the second output signal OUT2 when
and/ or phase reversal, of the three phases U , V , W of the 3 phase loss occurs in the second phase wire V . As shown in
three -phase alternating current. FIG . 3B , when phase loss occurs in the second phase wire
FIG . 2A shows a waveform diagram of the three -phase V , the first output signal OUT1 is a square wave signal and
alternating current in a normal phase state . As shown in FIG . the second output signal OUT2 is at a high electrical level.
2A , the three phases U , V, W of the three-phase alternating FIG . 3C shows waveform diagrams of the first output
current are respectively sine waves with a phase difference 40 signal OUT1 and the second output signal OUT2 when
of 120 degrees . FIG . 2B shows waveformsof the first output phase loss occurs in the third phase wire W . As shown in
signal OUT1 and the second output signal OUT2 when the FIG . 3C , when phase loss occurs in the third phase wire W ,
three -phase alternating current is in a normal phase state . As the first output signal OUT1 and the second output signal
shown in FIG . 2B , in a normal phase state , the first output OUT2 are square wave signals with the same phase .
signal OUT1 and the second output signal OUT2 are square 45 FIG . 3D shows waveform diagrams of the first output
wave signals that have a same period, and a rising edge of signal OUT1 and the second output signal OUT2 when
the first output signal OUT1 precedes a rising edge of the phase loss occurs in two or three phases of the first phase
second output signal OUT2 by 1/3 of a square wave period wire U , the second phase wire V and the third phase wire W .
(that is, a phase of the first output signal OUT1 precedes that As shown in FIG . 3D , when phase loss occurs in the third
of the second output signal OUT2 by 120 degrees ). 30 phase wire W , both the first output signal OUT1 and the
Table 1 shows states of the first output signal OUT1 and second output signal OUT2 are at high electrical levels .
the second output signal OUT2, when phase loss occurs in In this manner, a phase loss state of the three -phase
at least one phase of the three phases U , V , W according to alternating current may be detected by a simple circuit
this embodiment of the present invention . structure , and an output signal that indicates the phase loss
55 state of the three -phase alternating current is provided .
TABLE 1 Table 2 shows states of the first output signal OUT1 and
the second output signal OUT2 when phase reversal occurs
Number The phase state The states of OUT1 and OUT2 in two phases of the three phases U , V , W according to this
Phase loss occurs in the UOUT1 is at a high electrical level, embodiment of the present invention .
phase wire and OUT2 is a square wave 60
N
Phase loss occurs in the VOUT2 is at a high electrical level, TABLE 2
phase wire and OUT1 is a square wave
w
Phase loss occurs in the OUT1 and OUT2 have square Number The phase state The states of OUT1 and OUT2
W phase wire waves with the same phase
A
Phase loss occurs in the U Both OUT1 and OUT2 are at 1 Phase reversal occurs in the U OUT1 does not precede
phase wire and the V high electrical 65 phase wire and the V phase wire OUT2 by 1/3
phase wire levels of the square wave period
 US 9 , 759,756 B2
TABLE 2 - continued end 104 -2 of the second optical coupler 104 are connected
to the third phase wire W through the third sampling resistor
Number The phase state The states of OUT1 and OUT2 116 .
2 Phase reversal occurs in the U According to an embodiment of the present invention , the
phase wire and the W phase circuit for three -phase detection 100 may further include a
wire
??? Phase reversal occurs in the V first diode 118 and a second diode 120 . The first diode 118
phase wire and the W phase is connected between the first input end 102 - 1 and the
wire second input end 102 - 2 of the first optical coupler 102 . The
second diode 120 is connected between the first input end
As shown in Table 2 , when the first output signal OUT1 104 - 1 and the second input end 104 -2 of the second optical
does not precede the second output signal OUT2 by 113 of the coupler 104 . The first diode 118 and the second diode 120
square wave period , it indicates that phase reversal occurs in protect the optical couplers from being damaged by a
third phase
two phases of the first, second and third phase wires
wires .. InIn this
this reverse voltage .
case. waveforms of the first output signal OUT1 and the 15 According to an embodiment of the present invention, the
second output signal OUT2 are shown in FIG . 4 . circuit for three -phase detection 100 may further include a
According to this embodiment of the present invention , as first pull- up resistor 122 and a second pull- up resistor 124
shown in FIG . 1, the circuit for three -phase detection 100 that function as pull-up resistors for outputs of optical
may further include a micro control unit (MCU ) 106 , where couplers . The first output end 102- 3 of the first optical
the first output end 102 - 3 of the first optical coupler 102 and 20 coupler 102 is connected to a working voltage through the
the first output end 104 - 3 of the second optical coupler 104 first pull- up resistor 122 , and the first output end 104 - 3 of the
are respectively connected to a first input end and a second second optical coupler 104 is connected to the working
input end of the micro control unit through a first output voltage through the second pull- up resistor 124 . In this
resistor 108 and a second output resistor 110 respectively. embodiment, the working voltage is + 5V . A second output
Based on the first output signal OUT1 and the second output 25 end 102 -4 of the first optical coupler 102 and a second
signal OUT2 that are respectively from the first optical output end 104 -4 of the second optical coupler 104 are
coupler 102 and the second optical coupler 104 , the micro grounded .
control unit 106 detects the phase loss and / or phase reversal In an embodiment of the present invention , the circuit for
of the three- phase alternating current with reference to three -phase detection may just include two optical couplers
relationship (s ) shown in Table 1 and/ or Table 2 . The micro 30 for detecting a state of a three -phase alternating current, and
control unit 106 may be implemented by a general processor therefore, has simplified circuit structure and lower costs.
executing program instructions, or may be implemented by According to an embodiment of the present invention , the
a specific integrated circuit, or may be implemented by circuit for three -phase detection may be used to detect
completely a hardware circuit . According to this embodi phases of a three -phase alternating current of apparatus that
ment of the present invention , the micro control unit may 35 uses the three-phase alternating current, which will be
store a detection result, or generate an alarming signal or described below with reference to FIG . 5 , by taking a
turn off an electrical appliance when the phase loss and/ or compressor as an example .
phase reversal is detected . As shown in FIG . 5 , a compressor 500 may include a
In an implementation manner, when the first output signal compression member 510 , a motor 520 and the circuit for
OUT1 maintains a high electrical level and the second 40 three -phase detection 100 described above. The motor 520 is
output signal OUT2 is a square wave signal, the micro configured to drive the compression member 510 to com
control unit 106 detects that phase loss occurs in the first press media that enter the compressor 500, and the circuit for
phase wire U . When the second output signal OUT2 main - three -phase detection 100 is connected to the motor 520 , and
tains a high electrical level and the first output signal OUT1 is configured to detect a phase state of the motor 520 .
is a square wave signal, the micro control unit 106 detects 45 Optionally , the compressor 500 may further include : a
that phase loss occurs in the second phase wire V . When the control module 530 , configured to alarm and /or control
first output signal OUT1 and the second output signal OUT2 on / off of the motor according to the phase state that is
are square wave signals with the same phase , the micro detected by the circuit for three - phase detection 100 .
control unit 106 detects that phase loss occurs in the third FIG . 6 shows a flowchart of detecting phases of a three
phase wire W . When both the first output signal and the 50 phase alternating current of the compressor according to an
second output signal maintain high electrical levels, the embodiment of the present invention . As shown in FIG . 6 ,
micro control unit 106 detects that phase loss occurs in at in a state 610 , the circuit for three-phase detection 100 is
least two phases of the first, second and third phase wires. initially started in response to a start command, and turns on
When the first output signal OUT1 does not precede the a relay of the compressor, for example , in one second , to
second output signal OUT2 by 1/3 of the square wave period, 55 detect the phase state of the motor 520 . After the one second
the micro control unit 106 detects that phase reversal occurs expires , a state 620 , for example , a five - second detection
in two phases of the first, second , and third phase wires. window , is started . The circuit for three -phase detection 100
According to an embodiment of the present invention , as starts performing detection , for example , at the third second
shown in FIG . 1, the circuit for three - phase detection 100 of the five - second detection window , to prevent electrical
may further include a first sampling resistor 112 , a second 60 noise of an initial stage . If the five - second detection window
sampling resistor 114 , and a third sampling resistor 116 . The expires and the phases are good , it is determined that the
first input end 102 - 1 of the first optical coupler 102 is motor 520 is in a normal state 630, and the state 620 is
connected to the first phase wire U through the first sampling started again and the detection is continued . If the five
resistor 112 . The first input end 104 - 1 of the second optical second detection window expires and phase reversal and /or
coupler 104 is connected to the second phase wire V through 65 phase loss occurs, a state 640 is started to give an alarm by
the second sampling resistor 114 . Both the second input end using a sound or optical signal and optionally turn off the
102 - 2 of the first optical coupler 102 and the second input motor.
 US 9, 759 ,756 B2
A person skilled in the art may understand that, the phase loss occurs in at least two wires of the first,
embodiment shown in FIG . 6 is merely examples, and each second , and third phase wires .
time length may be changed according to an actual require - 2 . The circuit for three-phase detection according to claim
ment. For example , the relay of the compressor may be 1 , further comprising a micro control unit, wherein the micro
turned on in more than or less than one second , or it may 5 control unit comprises a first input end and a second input
take more than or less than one second from initial start to end , wherein the first output end of the first optical coupler
the first detection window . A time length of the detection is connected to the first input end of the micro control unit,
window may be more than five seconds, and may be and the first output end of the second optical coupler is
adjusted according to an actual requirement. In each detec - connected to the second input end of the micro control unit ;
tion window , the detection may be started at a time point 10 and
other than the third second of the detection window . The the micro control unit is configured to detect,based on the
detection process may include more or less states, to be first output signal and the second output signal, phase
adaptive to requirements of different application scenarios . loss and/or phase reversal of the three- phase alternating
According to embodiments of the present invention , current.
phases of a three-phase alternating current may be detected 15 3. The circuit for three- phase detection according to claim
by using two output signals and by using a simplified circuit. 1, wherein the first output signal and the second output
The circuit in the embodiments of the present invention is signal are square wave signals, and when a rising edge of the
simplified , fewer components are needed , and thereby pro - first output signal does not precede a rising edge of the
duction costs are obviously reduced while reliability is second output signal by 1/3 of a period of the square wave
improved . In addition , the micro control unit according to 20 signal, it indicates that phase reversal occurs in two wires of
the embodiments of the present invention may store a the first, second , and third phase wires .
detection result, facilitating later data analysis and product 4 . The circuit for three -phase detection according to claim
maintenance , or generating an alarm signal or turning off a 1 , further comprising:
power supply apparatus or electrical appliance when the first sampling resistor, wherein the first input end of the
phase loss and / or phase reversal is detected . Consequently, 25 first optical coupler is connected to the first phase wire
embodiments of the present invention may be used to through the first sampling resistor;
provide multiple functions, and can facilitate interaction a second sampling resistor, wherein the first input end of
with another detection device . the second optical coupler is connected to the second
The principle of the present invention is described above phase wire through the second sampling resistor ; and
with reference to specific embodiments. A person skilled in 30 a third sampling resistor, wherein the second input end of
the artmay understand that, details listed above are merely the first optical coupler and the second input end of the
used to describe rather than limit the present invention . Steps second optical coupler are connected to the third phase
included in the foregoing method may be implemented in wire through the third sampling resistor.
different sequences, provided that objectives of the present 5 . The circuit for three -phase detection according to claim
invention can be implemented in the sequence . The protec - 35 4 , further comprising :
tion scope of the present invention is defined by the a first diode , connected between the first input end and the
appended claims and an equivalent thereof. second input end of the first optical coupler, and
a second diode , connected between the first input end and
What is claimed is: the second input end of the second optical coupler.
1. A circuit for three -phase detection , comprising a first 40 6 . The circuit for three -phase detection according to claim
optical coupler and a second optical coupler ; wherein 4 , further comprising :
a first input end and a second input end of the first optical a first pull- up resistor, wherein the first output end of the
coupler are respectively connected to a first phase wire first optical coupler is connected to a working voltage
and a third phase wire of a power supply assembly , and through the first pull-up resistor ; and
a first output end of the first optical coupler provides a 45 a second pull - up resistor, wherein the first output end of
first output signal; and the second optical coupler is connected to the working
a first input end and a second input end of the second voltage through the second pull-up resistor, wherein
optical coupler are respectively connected to a second a second output end of the first optical coupler and a
phase wire and the third phase wire of the power supply second output end of the second optical coupler are
assembly, and a first output end of the second optical 50 grounded .
coupler provides a second output signal; 7 . A compressor, comprising: a compression member, a
wherein the first output signal and the second output motor, and a circuit for three - phase detection , wherein the
signal are used to indicate a phase state of a three -phase motor is configured to drive the compression member to
alternating current; compress a medium that enters the compressor ; and the
wherein when the first output signal maintains a high 55 circuit for three -phase detection is connected to the motor,
electrical level and the second output signal is a square and is configured to detect a phase state of the motor;
wave signal, it indicates that phase loss occurs in the wherein the circuit for three -phase detection comprises a
first phase wire ; first optical coupler and a second optical coupler ;
when the second output signal maintains a high electrical wherein
level and the first output signal is a square wave signal, 60 a first input end and a second input end of the first optical
it indicates that phase loss occurs in the second phase coupler are respectively connected to a first phase wire
wire ; and a third phase wire of a power supply assembly for
when the first output signal and the second output signal the motor, and a first output end of the first optical
are square wave signals with a same phase , it indicates coupler provides a first output signal; and
that phase loss occurs in the third phase wire ; and 65 a first input end and a second input end of the second
when both the first output signal and the second output optical coupler are respectively connected to a second
signal maintain high electrical levels, it indicates that phase wire and the third phase wire of the power supply
 US 9 ,759 ,756 B2
10
assembly , and a first output end of the second optical detecting, based on the first output signal and the second
coupler provides a second output signal; output signal, a phase state of a three - phase alternating
wherein the first output signal and the second output current of the power supply assembly ;
signal are used to indicate the phase state of a three wherein the detecting, based on the first output signal and
phase alternating current of the power supply assembly 5 the second output signal, the phase state of the three
phase alternating current comprises : detecting the
for the motor ; phase loss of the three - phase alternating current accord
wherein when the first output signal maintains a high ing to at least one of the following :
electrical level and the second output signal is a square when the first output signal maintains a high electrical
wave signal, it indicates that phase loss occurs in the 10 level and the second output signal is a square wave
first phase wire ; signal, determining that phase loss occurs in the first
when the second output signal maintains a high electrical phase wire ;
level and the first output signal is a square wave signal, when the second output signal maintains a high electrical
it indicates that phase loss occurs in the second phase level and the first output signal is a square wave signal,
wire; determining that phase loss occurs in the second phase
15
when the first output signal and the second output signal1 wire ;
when the first output signal and the second output signal
are square wave signals with a same phase , it indicates are square wave signals with a samephase, determining
that phase loss occurs in the third phase wire ; and that phase loss occurs in the third phase wire; and
when both the first output signal and the second output when both the first output signal and the second output
signal maintain high electrical levels , it indicates that 30 signal maintain high electrical levels , determining that
phase loss occurs in at least two wires of the first, phase loss occurs in at least two of the first, second, and
second, and third phase wires . third phase wires.
8 . The compressor according to claim 7 , further compris 11 . The method for three - phase detection according to
ing: a control module, configured to alarm and /or control
claim 10, wherein the detecting , based on the first output
on /off of the motor according to the phase state that is 2523 signal
detected by the circuit for three -phase detection. and the second output signal, the phase state of the
9. The compressor according to claim 8 , further compris three -phase alternating current comprises: detecting, based
ing a micro control unit, wherein the micro control unit on the first output signal and the second output signal, phase
comprises a first input end and a second input end , wherein loss and /or phase reversal of the three-phase alternating
the first output end of the first optical coupler is connected 3030 current.
to the first input end of the micro control unit , and the first 12 . The method for three- phase detection according to
output end of the second optical coupler is connected to the claim 10 , wherein the detecting , based on the first output
second input end of the micro control unit; and signal and the second output signal, the phase state of the
the micro control unit is configured to detect, based on the three - phase alternating current comprises: when both the
first output signal and the second output signal, phase 35 first output signal and the second output signal are square
loss and /or phase reversal of the three -phase alternating wave signals and a rising edge of the first output signal does
current. not precede a rising edge of the second output signal by 1/3
10. A method for three-phase detection , comprising : of a period of the square wave signal, determining that phase
receiving, by a first optical coupler, a signal of a first reversal occurs in two of the first, second , and third phase
phase wire and a signal of a third phase wire that are 10
from a power supply assembly, and outputting a first 40 claim13 . The method for three- phase detection according to
10 , further comprising : performing the method for
output signal according to the signal of the first phase three - phase detection circularly in a detection window until
wire and the signal of the third phase wire;of a second phase abnormality is detected .
receiving, by a second optical coupler, a signal of a second prio
phase wire and the signal of the third phase wire of the 45 14 . The method for three -phase detection according to
power supply assembly, and providing a second output 45 claim 13, further comprising : alarming and /or stopping
power supply when the phase abnormality is detected .
signal according to the signal of the second phase wire
and the signal of the third phase wire; and *