Research Journal of Applied Sciences, Engineering and Technology 4(22): 4884-4888, 2012
ISSN: 2040-7467
© Maxwell Scientific Organization, 2012
Submitted: May 19, 2012
Accepted: June 15, 2012
Published: November 15, 2012
The Online-Measurement System Design for the Temperature Rise of AC
Motor Winding Based on FFT
1
Haihong Xiao and 2Zhenjun Li
Department of Electrical and Information,
2
Department of Mechanical Engineering, Henan institute of engineering,
Zhenzhou 451191, China
1
Abstract: It is important to measure the temperature rise of AC motor winding and the common method
has many shortcomings, therefore the new design for measuring the temperature rise is necessary. The
paper mainly discusses the online-measurement system design for the temperature rise of AC motor
winding based on FFT. The principle of measuring temperature rise, measuring power and current based on
FFT are given in the study. At the same, some hard ware circuits, the main program flow chart and the
testing results are given. The result shows that the design feasible.
Keywords: Current, FFT, power, temperature rise
INTRODUCTION
According to the People’s Republic of China
standard of EN60335-1 and GB4706.1-2005, it is
necessary to measure the value of AC motor winding
temperature rise for getting the AC motor’s efficiency
and calculating the loss of motor winding heat. At the
same time, excessive temperature rising will cause the
security hidden danger to Electrical system and lead to
the accident occur. Formerly, the measurement method
is to test the DC resistance of the AC motor winding in
cold and hot state’s for calculating the temperature
rising. This method to test temperature rising lead to the
AC motor must be turned off the power firstly and the
error caused by time delay will produce and the method
must have been calculated, draw projections (Zhang
and Li, 1986). At present, the major intelligent
instrument to test temperature rising that exist in market
uses an additional direct current source method, which
is to measure voltage and resistance of winding to find
temperature (Yao and Shi, 2001). But this kind of
instrument has been complicated in structure,
troublesome in use, high in cost, single in function. So,
it is necessary to design a simple, practical, multifunction, online-measurement instrument. This paper
discusses the resistance of the online-measurement
instrument to test the temperature rising (Sun, 1997;
Dong, 2011; Song et al., 2007). Through to the sampling
of AC voltage and current and using FFT conversion
work out active power of the windings, find out
resistance and the temperature rising of windings. This
system in addition to measure temperature winding,
Also can measure motor line voltage, and current and
harmonic content, meanwhile it have a broad market
prospect.
WINDING TEMPERATURE MEASURING
PRINCIPLE AND THE WHOLE SYSTEM
DESIGN
Motor winding temperature measurement and AC
sample principle:
•
Motor winding temperature rising measurement
principle
According to the national Standard of EN60335and GB4706.1-2005.Motor winding temperature
measurement formula is:
∆ T=
where,
∆T =
R1 =
R2 =
K =
K =
K =
T1 =
T2 =
R2 − R1
× ( K + T1 ) − (T2 − T1 )
R1
(1)
The Winding's temperature rising
Resistance of winding in cold state
Resistance of winding in hot state
Constant,
235, with CU winding,
225 with AL winding
The temperature of cold state
The temperature of hot state
Because:
R=
P
I2
(2)
Corresponding Author: Department of Electrical and Information, Henan Institute of Engineering, Zhenzhou 451191, China
4884
Res. J. Appl. Sci. Eng. Technol., 4(22): 4884-4888, 2012
Voltage
sampling
circuit
Signal
processing
circuit
Signal shift
circuit
A/D
convert
circuit
Temperature detection
circuit and the others
Signal
processing
circuit
Cortex-M3
STM32
Current
sampling
circuit
PLL circuit
Keyboard
circuit
Fig. 1: The overall blog diagram
So:
∆T =
I RMS:
I P −I P
( K + T1 ) − (T2 − T1 )
I 22 P1
2
1 2
2
2 1
h=0
(3)
∞
PC = U 0 I 0 + ∑ U h I h cos ϕh
∞
PA = U 0 I 0 + ∑ U h I h cos ϕ h
PALL =P1 + P2
The power on each winding:
P=
Harmonic amplitude for h times:
(5)
ah
bh
(6)
According to above equation for h times:
U h = ah2 + bh2
I h = ah2 + bh2
U RMS: U =
N /2
∑U
h =0
2
h
(10)
h =1
(4)
2 N −1
T
2π
y (k ) cos(h
k)
∑
N K =0
N
N
2 N −1
T
2π
bh = ∑ y (k ) sin(h
k)
N K =0
N
N
Phase angle： φh = arc tg
(9)
Power for phase A:
ah =
ch = ah2 + bh2
(8)
h =1
The power and the current measurement principle
based on FFT
The signal waveform is discretized into:
N −1
a
y (t ) = 0 + ∑ ( ah cosh ω t + bh sinh ω t )
2 k =0
2
h
Power for phase C:
In equation (3)，P1，P2，I1，I2 are the power
and current value which are measured in cold state
and hot state, (I1 , I2 :IP in delta connection, IL in
star connection). T1, T2 are the same with equation
(1).
•
N /2
∑I
I =
(7)
PAL L
3
(11)
The design of overall system: The system mainly
consist of voltage sampling circuit, current sampling
circuit, temperature detection circuit, display circuit,
keyboard circuit, communication circuit, PLL circuit,
and Cortex-M3 STM32 interface circuit with A/D etc.
The overall block diagram is as Fig. 1.
In Fig. 1, two of the three phase current (IA, IC),
voltage (UAB, UCB) are sampled by CT and PT. Through
the same signal processing circuit, the two sampling
signal amplitude are shifted to fit to the A/D (max125).
In the design, the PLL circuit is designed to proceed the
synchronous signal which the out frequency is the N
times to the input frequency and the synchronous signal
is sent to STM32, to be used to start the A/D converter.
The Cortex-M3 STM32 is the mainly CPU, which is
used to control the whole hardware system and
calculate the voltage, current and power in RMS with
FFT. On the other hand, STM32 is used to measure the
temperature with the embedded A/D, to display, to
communicate, to store the data, etc.
4885 Res. J. Appl. Sci. Eng. Technol., 4(22): 4884-4888, 2012
voltage to the current firstly. Current transformer with
high accuracy, wide range of CT. When inputs current
being 5A, the current transformer outputs 10 mA. CT
transformer in series resistance 100 Ω to get 1V
voltage., Behind the voltage amplification circuit, the
input signal to the back of 4V, make the system able to
receive the impact of the current rated 120%.
The voltage transformer has complex structure
and the price is too high. So the voltage sampling
circuit uses the same the current sampling circuit
with series resistance in the current transformer
THE DESIGN OF SYSTEM HARDWARE
The system hardware consists of the voltage
sampling circuit, the current sampling circuit, display
circuit, signal (rate) output circuits, communication
circuit, etc. Because communication circuit, display
circuit, key circuit using conventional circuits, therefore,
without discourse in this paper.
The design of Voltage, current sampling circuit: The
current sampling circuit shown in Fig. 2, the voltage
sampling uses the same circuit, which convert the
Fig. 2: Current sampling circuit
R311K
R2
+5
100K
11
9
10
INH
GND
U1A
R1
C1
LM393JG1K 0.1uF
1
14
4
D1
1N4148
SIG IN
VCO OUT
C3
GND
30pF
GND
5
7
16
Q14
Q13
Q12
Q10
Q9
Q8
Q7
Q6
Q5
Q4
GND
8
12
CLK0
10
CLK0
9
VDD RST
CLK1
GND
Fig. 3: The PLL circuit
4886 U25
8
GND
ZENER
15
-5
1
1
2
2
3
100nF
1K
R1 TOGND
3
R2 TOGND
12
2
VCOIN
1
DMD
CI 2
7
15
PHPULSES
13
PHCMPR1
14
PHCMPR2 CI 1
6
6
VDD
CMPRIN
3
4
8
Signal
13
16
+5
R4
C2
4
HCF4046BEY
U3
CD4060BCN
11
Output
Res. J. Appl. Sci. Eng. Technol., 4(22): 4884-4888, 2012
U2
U1
GND
Uab 4
3
Ia 2
1
Ucb34
35
Ic 32
33
25
PA5
INT1
PD2
PA6
PA7
29
30
26
28
27
8
36
18
CH1A
CH1B
CH2A
CH2B
CH3A
CH3B
CH4A
CH4B
CLK
CONVST
INT
CS
RD
WR
AVDD
DVDD
AVSS
D0/A0(LSB)
D1/A1
D2/A2
D3/A3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13(MSB)
AGND
AGND
DGND
REFIN
REFOUT
5
17 +5V
31
C1
24
23
22
21
20
19
16
15
14
13
12
11
10
9
3V3
22
PA3 2
D0
D1
D2
D3
D4
D5
D6
D7
3
4
5
6
7
8
9
10
U3
OE
DIR
A1
A2
A3
A4
A5
A6
A7
A8
VCCB
VCCB
VCCA
B1
B2
B3
B4
B5
B6
B7
B8
104
GND
D0
D1
D2
D3
11
D4
GND
12
D5
GND
13
D6
GND
D7
GND SN74LVC4245DB
D8
+5V
D9
U4
D10
22
D11
OE
VCCB
2
D12
DIR
VCCB
D13
VCCA
GND
D8 3
A1
B1
D9 4
A2
B2
D10 5
A3
B3
D11 6
A4
B4
D12 7
A5
B5
D13 8
A6
B6
9
INT
A7
B7
CLK0 10
A8
B8
11
12
13
6
7
GND
MAX125ACAX
24
23
1
21
20
19
18
17
16
15
14
+5V
PC0
PC1
PC2
PC3
PC4
PC5
PC6
PC7
3V3
24
23
1
21
20
19
18
17
16
15
14
PA0
PA1
PA2
PA3
PA4
PA5
PA6
PA7
14
15
16
17
20
21
22
23
PA8
PA9
PA10
PA11
PA12
PA13
PA14
PA15
41
42
43
44
45
46
49
50
PD2
5
6
54
BOOT0 60
RESET
7
PA0-WKUP
PA1
PA2
PA3
PA4
PA5
PA6
PA7
PA8
PA9
PA10
PA11
PA12
PA13/JTMS/SWDIO
PA14/JTCK/SWCLK
PA15/JTDI
OSC_IN/PD0
OSC_OUT/PD1
PD2
BOOT0
NRST
PC8
PC9
PC10
PC11
PC12
PC13
PA4
PA2
3V3
GND
GND
GND
1
32
48
64
19
SN74LVC4245DB
U5A
INT1 1
2 INT
13
VBAT
PB8
PB9
PB10
PB11
PB12
PB13
PB14
PB15
PC0
PC1
PC2
PC3
PC4
PC5
PC6
PC7
PC8
PC9
PC10
PC11
PC12
PC13-TAMPER-RTC
PC14-OSC32_IN
PC15-OSC32_OUT
VDD_1
VDD_2
VDD_3
VDD_4
VSS_1
VSS_2
VSS_3
VSS_4
VDDA
VSSA
STM32F103RBT6
SN74LS04D
PB0
PB1
PB2/BOOT1
PB3/JTDO
PB4/JNTRST
PB5
PB6
PB7
26
27
28
55
56
57
58
59
PB0
PB1
PB2
PB3
PB4
PB5
PB6
PB7
61
62
29
30
33
34
35
36
PB8
PB9
PB10
PB11
PB12
PB13
PB14
PB15
8
9
10
11
24
25
37
38
PC0
PC1
PC2
PC3
PC4
PC5
PC6
PC7
39
40
51
52
53
2
3
4
PC8
PC9
PC10
PC11
PC12
PC13
PC14
PC15
31
47
63
18
12
GND
Fig. 4: A/D and cortex-M3 interface circuit
The design of PLL circuit: The PLL circuit is
designed for sampling voltage and current signal in
equal interval time, the principle circuit is shown as
Fig. 3.
In Fig. 3, the LM339 is used to change analog sine
signal to square wave signal and the CD4060 is used for
an divider circuit with 64.
CD4046 is a PLL IC circuit, which the output
signal is 64 times frequency to the frequency.
The design of the STM32 interface circuit with A/D
convert: Two A/D chip named MAX125 are used in
the measurement system, the interface circuit with
Cortex-M3 is as Fig. 4.
Three phase voltage and current signals are
converted by two MAX125, which outputs the highest
level is 5V. So an IC chip 74AHCT4245 is necessary to
match the 3.3V voltage level of STM32. Two
74AHCT245 are used in this circuit as level shifter
unit. 74AHCT4245 output signals and input signals are
connected, respectively to MAX125 and STM32 with
14-bit DBUS.
The control signals’ voltage level is matched just
as data signal. Equally spaced signal that comes from
PLL and the signal of A/D conversion completed are
shifted by 74AHCT4245 .The signals that two
MAX125 receive, respectively are UAB, UCB, IA and IC. The design of system software: The system software
is used to measure the power of each winding, the
current, the temperature, to complete FFT calculation,
and to calculate the temperature rising of winding. The
subroutines in the internal library of Cortex-M3 are
applied as calculation program. The flow chart is shown
in Fig. 5.
In the main flow charts, initialization of the system
is firstly been done. Then other work will be done One
by one. The other study concludes starting A/D to
complete sampling 64 times in one voltage cycle,
calculating the power and the current of each winding,
calculating the temperature rising of one winding, etc.
At the specific time, the power, current, room
temperature are stored in flash memory to be used to
calculate the winding temperature rising.
The method to test the system and the experimental
result: To test the performance of the system, AC
motor named YS8024 is been used in no-load state and
with Laboratory temperature condition. The HP34401
is used to test the resistance of each winding in cold and
hot state, and the system is used to test the power and
current, the test data is shown in Table 1. In Table 1
cold state is defined at the time that the motor start to
work, and the hot state is defined the motor works one
hour after. The data is respectively substituted into
Eq. (1) and (3), to calculate the temperature rise that is
named as ∆T.
4887 Res. J. Appl. Sci. Eng. Technol., 4(22): 4884-4888, 2012
experimental results show that the system has high
accuracy, low cost, convenient debug, having a broad
application prospect.
Start
Initialization
ACKNOWLEDGMENT
Sampling
interrupt?
Complete 64
times sampling
In the design process, Xu Yuwei, studying in the
Electronic and information
Department, Henan
institute of engineering, do a lot of work in the
hardware and software design. In the thesis writing
process, He Yongtao gave me a lot of help , expressing
gratitude together.
Store the P and I
and T in cold
or hot state
Calculate power,
current and test room
temperature
REFERENCES
Store the data in
the specific time?
Calculate
temperature rising
End the test
Fig. 5: Main flow chart of the system
Table 1: The testing data
Resistance
Cold state
8.0
Hot state
8.9
29.25
∆T
Power of each phase
15.98
18.88
29.27
Current
1.414
1.417
In Table 1, the room temperature is defined to
25°C，the calculating result shows the temperature rise
are the same with the two measuring method.
Dong, G., 2011. Measurement and Calculation of the
Motor Winding Temperature Rise. Suzhou Institute
of Trade and Commerce, Suzhou 215009, China.
Song, Q., W. Zhi-fu, Z. Cheng-ning and S. Feng-chun,
2007.
Measurement
of
Motor
Winding
Temperature Based on Zero Second Resistance
Fitting. School of Mechanical and Vehicular
Engineering, Beijing Institute of Technology,
Beijing 100081, China.
Sun, Y., 1997. Measurement of the motor winding
temperature rise. Elect. Meas. Ins., Vol: pp.
Yao, X. and R. Shi, 2001. The Design of Online Test
Instrument of Motor winding temperature rise.
Microelectron. Comp., Vol: pp.
Zhang, J. and J. Li, 1986. The application of single
board computer in measuring temperature rise of
motor winding. Micro motor, Vol: pp.
CONCLUSION
This system is designed for measuring the
temperature rising of AC motor winding, the
4888