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RTCA SC-135 and EUROCAE WG-14
Change Proposal Form
(One major comment per form.
Shaded blocks for committee use only.)
SC-135 Paper Number:
Date:
DO-160E Section:
Rev F #088E
1 March 06
16
Author’s Name, Affiliation, and E-mail:
Paragraph:
Page:
Paul Schwerman, WG16, Honeywell.
16.7.2
[email protected]
Reason for Change:
Inrush currents need to be controlled in order to control the power quality in an aircraft.
Note: The first millisecond usually consists of charging the EMI filter. Instead of ignoring the first
millisecond, the test conditions are loosened to avoid making the test too onerous. SSPCs are driving the
monitoring of the inrush current during the first millisecond. To make the inrush test repeatable and to not
overly penalize for input capacitance in the EMI filter, the resistance between the power source and the
EUT will be controlled.
Proposal Disposition:
Accepted As Written
Withdrawn
Accepted As Modified
Rejected
Other
Rejection Reason:
Proposal Deferred To:
RTCA SC-135 Concurrence
Proposal Disposition By:
EUROCAE WG-14 Concurrence
Date:
Revise From:
New paragraph
Proposal Page Number:
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SC-135 Change Proposal Form Rev C
Revise To:
16.2
Inrush Current Control: Designation I:
This designation is assigned to ac or dc equipment that meets the inrush current requirements
specified for designation I.
---------------------------------------------------------------------------16.7.2 Inrush Current Requirements (ac and dc).
16.7.2.1 Definition
The following requirements shall be met for equipment with designation I. Equipment that meets
an alternate inrush test is to claim designation Z. Equipment that does not test inrush is to be
marked with designation X.
16.7.2.2 Requirements
When the nominal input voltage is abruptly applied, the peak inrush current shall be less than
10times maximum nominal load peak for the first 2.0 milliseconds,
4 times maximum nominal load peak up to 500 msec, and
twice up to 2 seconds and nominal there after.
The unloaded test is to provide 115 +/- 1V rms ac, 28.0 +/- 0.25 V dc or 270V +/- 2.7V. The
loaded test is to provide 115 +/- 2V rms ac, 28.0 +/- 0.50 V dc or 270V +/- 5.4V at the power
source's regulation point. The voltage rise time and fall time is to be less than 1/4 cycle for ac or
less than 300 usec for dc.
At the maximum load current draw, add a resistor between the power source and each EUT
power input hot lead to adjust the measured voltage drop between the power source and EUT to
the following:
3.0V +/- 0.3V rms ac for 115V ac equipment with power source set to 115V +/- 1V rms ac
1.0V +/- 0.1V dc for 28V dc equipment with power source set to 28V +/- 0.25V dc..
9.0V +/- 0.9V for 270V dc equipment with power source set to 270V +/- 2.7V dc
This voltage drop is to be measure within 7 inches of the regulation point of the power source and
within 7 inches the EUTs input terminal.
Test Condition 1:
With the equipment stationary and unpowered for a minimum of 5 minutes, apply nominal
input voltage and verify that the equipment meets the requirements of this section.
Test Condition 2:
With the equipment stabilized and in its maximum input current operating mode, reduce
the input voltage to less than 5% of nominal for a period of 200 +20/-0 msec and then
apply nominal input voltage and verify that the equipment meets the requirements of this
section.
Notes:
1. This test shall be performed with a frequency of:
Proposal Page Number:
2 of 4
SC-135 Change Proposal Form Rev C
2.

400 +5/-0 Hz for A(CF) category equipment

360 +5/-0 Hz for variable frequency equipment then repeated with 650 +5/-0 Hz for
A(NF) category equipment and 800 +5/-0 Hz for A(WF) category equipment.
Abrupt application or removal of ac power occuring at the zero crossing of the ac voltage
waveform is considered to meet the rise time requirements.
As Modified Text:
For reference: Klixon® 2TC Series breaker curves.
The 20X number is being questions. 10X is preferred by Boeing. Box designers want a higher limit
to cover noise at beginning.
An example inrush current test with 0.14 ohm series impedance (instead of an allowed 0.67 ohms)
between 28V source and EUT is shown below. The double leading edge spikes are cause by the
contact bounce of the mechanical switch used to run the test. The light blue line is the voltage at
the EUT terminals. The dark blue line is the current into the EUT.
Proposal Page Number:
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SC-135 Change Proposal Form Rev C
Question:
Add different letter for thermal vs Electronic CB curves? No, not at this time
Kamiar/ Evelyn wish to add more stringent requirements for first 2 msec for loads over several
kVA. Boeing and Airbus agree to allow 10X for smaller loads for first 2 msec.
Mike Smith (SSPC manufacture) to look at this spec.
Test method should be representative of aircraft regulating voltage at POR with line impedance to
UUT.
Note: 25 ohms (50 ohm in parallel with 50 ohms) and 1 uF gives a 6.37 kHz - 3dB point if we
bandwidth limit the current probe. Airbus does not want to bandwidth limit the current probe.
Jean-Paul needs the first msec to be controlled for SSPCs.
Note: Mario suggests a different standardization of the inrush voltage drops similar to:.
Test set is to deliver 10 cycle min at 10X nominal current with TBD +/- TBD voltage drop from nominal.
Test set is to deliver 100 cycle min at 4X nominal current with TBD +/- TBD voltage drop from nominal.
0.5V drop for 14V
Proposal Page Number:
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SC-135 Change Proposal Form Rev C