IVT 09LR-N, Service Manual

Page: 16 / 64

12LRN
2 – 11
2.2.1 Detailed explanation of PAM drive circuit sequence
2.2.2 AC clock (zero-cross) judgment
• The clock circuit determines the time from one rising point of the clock waveform to the next rising point.
The detected clock waveform is used to judge the power source frequency (50 Hz).
• The zero-cross of the AC voltage is judged as the rising of the clock waveform, as shown in the diagram above.
2.2.3 IGBT ON start time (delay time B)
• Based on the zero-cross of the AC voltage, the IGBT turns ON after a delay time set according to the power source frequency.
2.2.4 IGBT ON time (C)
• After the above delay time, the IGBT turns ON to supply a current to the reactor.
• The ON time of the IGBT determines the amount of energy (level of DC voltage rise) supplied to the reactor.
DC voltage level in each operation mode (varies depending on external load conditions)
– Cooling operation --- 260 to 280 V
– Heating operation --- 260 to 290 V
2.3. PAM protection circuit
To prevent excessive voltage of PAM output from damaging the IPM and electrolytic capacitor as well as the control printed circuit board (PCB), this
circuit monitors the PAM output voltage and turns off the PAM control signal and PAM drive immediately when an abnormal voltage output is gener-
ated. At the same time, it shuts off the compressor operation.
The protection voltage level is as follows.
2.3.1 Details of troubleshooting procedure for PAM
1) PAM shutdown due to error
1) When the DC voltage detection circuit sends a signal exceeding the specified voltage to the microcomputer
DC voltage of 400 V or higher (detection circuit input voltage of about 8.4 V or higher) [IC8 pin (4)]
– When an error is detected
• PAM IGBT turns OFF.
• Compressor turns OFF.
• All units shut down completely when the error occurs four times.
2) When the outdoor unit clock waveform differs from the specified value immediately before the PAM IGBT turns ON
When there is no clock waveform input
When a clock signal of other specified power source frequency (50 Hz) is input
– When an error is detected
• PAM IGBT does not turn ON.
• Compressor operates normally.
• Complete shutdown does not occur.
AC voltage waveform
Clock
IGBT ON
A
B C
A
B
C
50Hz
1.2mS
2.6mS
0.25 2.3mS
R125
270K
１／２Ｗ
Ｆ
C10
C9
550uF
400V
0V
D19
(Overvoltage detection)
IC1
69
5V
550uF
400V
R126
270K
１／２Ｗ
Ｆ
R127
13K
R128
13K
50
Ｖ
0.01uF
C87
DC Voltage
Ω
Ω
Ω Ω