■
Install inrush current limiting resistor(TFR1) between R terminal and +BC terminal.
■
If TFR1 is not connected, the power supply will not work.
■
The surge capacity is required for TFR1.
■
Wirewound resistor with thermal cut-offs type is required.
■
Inrush current limiting resistor can be used to limit the primary inrush current. However,
the secondary inrush current can’t be limited by increasing the resistor value of inrush
current limiting resistor. The secondary inrush current is approx. 25 ~ 30A.
Therefore, we don’t recommend connecting a large resistance as TFR1.
■
The inrush current changes by PCB pattern, parts characteristic etc.
Check the actual inrush current value flowing through the AC line.
Table 2.5
Recommended
resistor TFR1
■The selection method of TFR1 is shown below.
・
Calculation of resistance
Resistance can be calculated using the following formula.
TFR1
:
Inrush current limiting resistor
RL
:
Line impedance
Vin
:
Input voltage (rms)
Ip
:
Primary Inrush current (peak)
・
Calculation of required surge capacity
Required surge capacity can be calculated using the following formula.
Please contact to the component manufacturer regarding the surge current
withstanding capability.
I2t
:
Current squared times
TFR1
:
Inrush current limiting resistor
Cbc
:
Smoothing capacitor for boost voltage
Vin
:
Input voltage (rms)
■
If you need to meet the safety standards, install a discharging resistor R1 at input
interphase capacitors.
■
Please select a resistor so that the input interphase voltage decreases in 42.4V or less
at 1 second after turn off the input.
■
Fig.2.7 shows the relationship between a necessary resistance of R1 and total capacitance
of input interphase capacitors. The data is the value assuming the worst condition.
■
Please keep margin for rated voltage and power of R1.
Fig.2.7
Relationship
between input
interphase
capacitors
and discharging
resistor R1.
2.8 Inrush current limiting resistor: TFR1
2.9 Discharging resistor: R1
A-7
Recommended resistance
4.7Ω
～
22Ω
Applications Manual
TUNS1200
]
[
2
1
−
=
L
R
Ip
Vin
TFR
0
50
100
150
200
250
300
350
400
450
500
0
1
2
3
4
5
6
7
8
9
10
R
1
［
kΩ
］
Total capacitance of input interphase capacitors
［μF］
100VAC
200VAC
277VAC
]
[
1
2
2
2
s
A
TFR
Vin
Cbc
t
I
=
