Mid-Continent Instrument MD50 series Technical Document

INSTALLATION MANUAL AND
OPERATING INSTRUCTIONS
MD50-( ) Series
Static Electrical Power Inverter
REV. D February 24, 2011 MANUAL NUMBER 9017039
MID-CONTINENT INSTRUMENT CO., INC.
9400 E. 34th Street N., Wichita, KS 67226 USA
phone [phone] •fax [phone] •web www.mcico.com

REV. D February 24, 2011 2 Manual Number 9017039
FOREWORD
This manual provides information intended for use by persons who, in accordance with current regulatory
requirements, are qualified to install this equipment. If further information is required, please contact:
Mid-Continent Instruments
Attn: Customer Service Dept.
9400 E. 34th ST North
Wichita, KS 67226 USA
Phone [phone] Fax [phone]
We welcome your comments concerning this manual. Although every effort has been made to keep it
free of errors, some may occur. When reporting a specific problem, please describe it briefly and include
the manual part number, the paragraph/figure/table number, and the page number. Send your
comments to:
Mid-Continent Instruments
Attn: Technical Publications
9400 E. 34th ST North
Wichita, KS 67226 USA
Phone [phone], Fax [phone]
[email protected]
www.mcico.com
©Copyright 2010
Mid-Continent Instrument Co., Inc.

REV. D February 24, 2011 3 Manual Number 9017039
REVISION DETAIL
Rev. Date Approved Detail
A 02/26/10 BAW/JRC Initial release.
B 07/06/10 BAW/MKN Update Section 2.4 to add limitation statement regarding output.
C 07/20/10 MKN/BAW Update unit picture with True Blue Power label.
D 02/24/11 JDS/BAW Added section 3.3.2, and figure 3.4.

REV. D February 24, 2011 4 Manual Number 9017039
TABLE OF CONTENTS
SECTION 1 GENERAL DESCRIPTION
1.1 INTRODUCTION
1.2 TECHNICAL SPECIFICATIONS
1.2.1 ELECTRICAL ATTRIBUTES
1.2.2 PHYSICAL ATTRIBUTES
1.2.3 QUALIFICATIONS
SECTION 2 INSTALLATION CONSIDERATIONS
2.1 COOLING
2.2 EQUIPMENT LOCATION
2.3 ROUTING OF CABLES
2.4 LIMITATIONS
SECTION 3 INSTALLATION PROCEDURE
3.1 GENERAL INFORMATION
3.2 UNPACKING AND INSPECTING
3.3 CABLE HARNESS
3.3.1 WIRE GAUGE SELECTION
3.3.2 PIN ASSIGNMENT INFORMATION
3.3.3 HARNESS VERIFICATION
3.4 MOUNTING
3.5 INSTALLATION COMPLETION
SECTION 4 OPERATION
4.1 ELECTRICAL PERFORMANCE
4.2 PROTECTIVE FEATURES
SECTION 5 CONFORMANCE
5.1 CONTINUED AIRWORTHINESS STATEMENT
5.2 ENVIRONMENTAL QUALIFICATION STATEMENT
NUMBER LIST OF TABLES AND FIGURES
1.1 MODELS TABLE
1.2 PHYSICAL ATTRIBUTES TABLE
1.3 PERFORMANCE TABLE
3.3 CONNECTOR PINOUT FIGURE
3.3 CONNECTOR PINOUT TABLE
3.4 EXAMPLE WIRING DIAGRAMS
3.5 MD50 OUTLINE DRAWING FIGURE
3.6 MD50 MOUNTING ADAPTER FIGURE
4.1 THD PERFORMANCE
4.2 TEMPERATURE PERFORMANCE

REV. D February 24, 2011 5 Manual Number 9017039
SECTION 1 GENERAL DESCRIPTION
1.1 INTRODUCTION
The model MD50 series Static Electrical Power Inverter is a lightweight power converter that translates a
20 to 36 VDC input to a 115 VAC output at 60 Hertz and provides 500 watts (VA) of power. The
alternating current output is defined as a pure sine wave with less than 3% of total harmonic distortion
for clean, noise-free, harmonic-free power to supply nearly any common commercial or consumer load
rated for a nominal input of 115VAC. The MD50 series Inverter is FAA certified to TSO C73 and tested to
rigorous environmental standards and levels of RTCA DO-160. The small size and light weight in
conjunction with its installation flexibility inside or outside the pressure vessel make it an ideal choice for
aircraft power needs while reducing the challenges associated with other similar products.
Highlighted features include short circuit protection, overload capability, low voltage shut-down,
temperature monitoring, a self-resettable over-temperature disable, and a remote on/off function. The
rugged extrusion that houses the unit is designed to help dissipate heat and provide mechanical strength
against vibration or other possibilities of damage. Two independent fans allow for a smaller unit and
provide a quieter operation while keeping the internal components cool and extending the life of the unit.
1.2 TECHNICAL SPECIFICATIONS
1.2.1 ELECTRICAL ATTRIBUTES
Characteristics:
Input Voltage: Rated 28VDC nominal; 20-36VDC certified
Input Power: 17-25 amps; 0.2A at no load
Output Voltage: 115VAC ±3% at 60 Hertz ±0.1% (single phase)
Output Power: 500 watts (500 VA at power factor = 1)
Output Waveform: Pure sine wave
Power Factor: -0.8 to +0.8
Efficiency: 88% nominal
Total Harmonic Distortion (THD): < 3%; See Figure 4.1
Table 1.1
1.2.2 PHYSICAL ATTRIBUTES
Characteristics:
Weight: 3.9 pounds
Dimensions:
(not including connector mate) 6.71 inches long (8.15 inches – mounting base) 6.34 inches wide
2.74 inches high
Mating Connector (and cable clamp): MS3106A-18-9S or equivalent (MCI P/N 9016905-1 and -2)
Mounting: Base mount – orientation not critical
Table 1.2
1.2.3 QUALIFICATIONS
Specifications:
Qualification: FAA TSO-C73
Environmental Qualification: RTCA DO-160F Environmental Category
F3(Y)S2BB(RCC1)XXXXXXZXXXXXBXXXXX
Altitude: -15,000 ft to +55,000 ft
Temperature: -55°C to +70°C (-67°F to +158°F); See Figure 4.2
Table 1.3

REV. D February 24, 2011 6 Manual Number 9017039
SECTION 2 PRE-INSTALLATION CONSIDERATIONS
2.1 COOLING
No external cooling is required. The unit is equipped with two internal brushless DC fans. Restriction to
airflow can cause overheating of the unit and limit performance or reduce the expected life of the
product. Make sure to provide adequate clearance on both ends of the unit with the hexagonal openings
to allow for proper circulation. In general, four to six inches of clearance on both ends of the unit should
be acceptable. Mounting the unit to a metal surface can also help reduce the effects of temperature
within the unit but is not required.
2.2 EQUIPMENT LOCATION
The MD50 Static Inverter is designed for mounting flexibility, allowing for installation inside or outside the
pressure vessel with no requirement for temperature control. In addition to altitude and temperature
resistance, the unit is also designed to withstand high levels of condensing humidity. However,
installation locations where the unit could be subject to standing or direct water exposure should be
avoided. The unit can be mounted in any orientation. Clearance should be provided for the mating
connector and may require as much as four to five inches past the unit connector to allow for the
backshell, access to the connector, and appropriate wire bends.
2.3 ROUTING OF CABLES
The wires and cable bundle associated with the unit are heavy gauge wire and carry significant power. Be
aware of routing cables near other electronics or with other wire bundles that may be susceptible to high
energy flow.
Avoid sharp bends in cabling and routing near aircraft control cables. Also avoid proximity and contact
with aircraft structures, avionics equipment, or other obstructions that could chafe wires during flight and
cause undesirable effects.
2.4 LIMITATIONS
The MD50-( ) Series of static electric power inverters is certified to FAA TSO-C73 with the following
limitations identified:
1) Alternating current (AC) output is provided at 115 volts and 60 hertz in lieu of 115 volts and 400
hertz as identified in the MPS of the TSO.
2) Equivalent environmental qualification was verified per RTCA DO-160F in lieu of those identified
within the MPS of the TSO.
The conditions and tests for TSO approval of this article are minimum performance standards. Those
installing this article, on or in a specific type or class of aircraft, must determine that the aircraft
installation conditions are within the TSO standards, specification of the article, and deviations as listed
above. TSO articles must have separate approval for installation in an aircraft. The article may be
installed only according to 14 CFR part 43 or the applicable airworthiness requirements.

REV. D February 24, 2011 7 Manual Number 9017039
SECTION 3 INSTALLATION PROCEDURES
3.1 GENERAL INFORMATION
This section contains interconnect diagrams, mounting dimensions and other information pertaining to
the installation of the MD50 Static Inverter. After installation of cabling and before installation of the
equipment, ensure that power is applied only to the pins specified in the interconnect diagram.
3.2 UNPACKING AND INSPECTING EQUIPMENT
When unpacking this equipment, make a visual inspection for evidence of any damage that may have
incurred during shipment. The following parts should be included:
a. Static Inverter – MCI P/N MD50 [or MD50-( )]
b. Mating Connector (& cable clamp) – MCI P/N 9016905-1 (and 9016905-2)
c. Installation Manual – MCI P/N 9017039
Optional equipment available:
a. Mounting Adapter Kit – MCI P/N 9017040
Equipment not provided:
a. Mounting Hardware – four (4) #10-32 pan head screws
#10 lock washers (optional)
b. Cable Harness Wire – See Section 3.3 for specification
3.3 CABLE HARNESS
Construct the cable harness with regards to the instructions below, and using the Connector Pinout of
Figure 3.3, Figure 3.4, and Wiring Diagram of Table 3.3.
Refer to Section 2: Pre-Installation Considerations in regards to routing precautions.
3.3.1 WIRE GAUGE SELECTION
Use of PTFE, ETFE, TFE, Teflon, or tefzel insulated wire is recommended for aircraft use. Use
the following wire gauges for each of the pins in the connector:
Pin A and D – 12 AWG stranded or solid
Pin B and C – 16 AWG stranded or solid
Pin E and G – 16-24 AWG stranded or solid
3.3.2 PIN ASSIGNMENT INFORMATION
INPUT POWER:
Pin A – Positive DC input +24 to 32 VDC. Connect to the aircraft 28 VDC bus using a 25 or
30 Amp circuit breaker.
Pin D – Negative DC input. Internally this pin is connected to the inverter enclosure. Connect
to aircraft ground.

REV. D February 24, 2011 8 Manual Number 9017039
INVERTER OUPUT:
Pin B – AC Output 115VAC, 60Hz. Used for powering devices where terrestrial/utility power
designations are used, pin B can be connected as “Line” or “Hot”.
Pin C – AC Return 115VAC, 60Hz. Used for powering devices where terrestrial/utility power
designations are used, pin C can be connected as “Neutral”.
Note: Use of a circuit breaker on the AC output is optional. For the full
inverter 500VA output, a 5 Amp circuit breaker is sufficient. For convenience
at each AC outlet, individual circuit breakers of 1 to 2 amps each can be
used. If a single pole breaker is used, install the breaker on the wire from
pin B. If a double pole breaker is installed, route both pins B and C through
the circuit breaker.
REMOTE ON/OFF CONTROL: (see section 4.2.1)
Pin E – Remote ON/OFF Control. Connecting this pin to either DC Negative or to inverter pin
G will enable the AC output of the inverter. By utilizing a switch between this pin and ground
or negative, it will allow remote on/off control of the unit. When unconnected (output is OFF)
this pin will have approximately 11 VDC present, internally limited to less than 1 mA. If the
inverter is to be enabled at all times, pin E can be connected to pin G.
Pin G – Remote ON/OFF Return. This pin is internally connected to pin D and the enclosure.
Pin G can be used as the return from an ON/OFF switch or left unconnected. It is
recommended that pin G not be connected directly to ground or 28V negative.
Pin F – Reserved. Do not use.
FIGURE 3.3 TABLE 3.3
PINOUT VIEW OF CONNECTOR PINOUT
UNIT CONNECTOR
Pin #
A 24-32VDC Input
B 115VAC Output
C Output Return
D Input Return
E Remote On/Off
F Reserved
G Remote Return
Connector Pinout
A
D
B
E
C
F
G

REV. D February 24, 2011 9 Manual Number 9017039
FIGURE 3.4
EXAMPLE WIRING DIAGRAMS
MD50
A
D
G
E
B
C
28VDC
Case attached to airframe
INVERTER ENABLE
(always active)
28VDC
PROTECTION
&
GFI OUTLETS
ON
OFF
MD50
30A
30A
3rd Party
equipment
Optional 5A
Circuit Breaker
A
D
G
E
B
C
Case attached to airframe
A
D
G
E
B
C
A
D
G
E
B
C(not supplied)
Optional 1-2A
Circuit Breakers
110VAC Outlet(s)
(not supplied)
INVERTER ENABLE
(Remote ON/OFF)
3
21
AB
GFI
Ground Fault Indicator
(not supplied)
Optional
Notes:
1. Wiring diagrams above represent various examples of typical installations.
2. Recommended to attach case to metal aircraft structure.
3. Recommended outlet protection may consist of either:
A. single 5A circuit breaker for all outlet(s) (single or double pole breaker), OR
B. 1-2A circuit breakers for each outlet
4. For Remote On/Off operation, return line can be configured in one of three ways:
1. return line connected to pin G
2. return line connceted to pin D
3. return line connected to aircraft ground

REV. D February 24, 2011 10 Manual Number 9017039
3.3.3 HARNESS VERIFICATION
With the MD50 Static Inverter disconnected, activate the aircraft power bus that supplies the
unit and use an multi-meter to verify that aircraft power and ground with appropriate voltage
is on the pins within the mating harness.
3.4 MOUNTING
Refer to Section 2: Pre-Installation Considerations in regards to equipment location.
The MD50 Static Inverter is designed for base mounting only. Four #10-32 mounting holes should be
provided in the aircraft in accordance with Figure 3.5. If installing the MD50 as a replacement for legacy
static inverters, an optional Mounting Adapter Kit adapter plate is available to utilize the same mounting
hole locations. See figure 3.6 for mounting hole locations using the Mounting Adapter Kit and Section 3.2
for the Mounting Adapter Kit part number. Secure the unit with four #10-32 pan head phillips screws or
equivalent. A lock washer under the head of each screw is recommended.
3.5 INSTALLATION COMPLETION
Prior to operating the unit in the aircraft, it is recommended to verify the output and functionality of the
unit. In order to prevent accidental damage to other systems, it is best not attach the output to other
equipment or power busses prior to verification. Verify the output of the unit at the terminating end of
the cable with a multimeter to ensure proper voltage and polarity. Once verified, installation can be
completed and functionality of the remote on/off feature (if used) should be checked.

REV. D February 24, 2011 11 Manual Number 9017039
2.74
8.15 7.40 6.70
3.75
6.34
Connector per
MS3102A-18-9P
(4X) Ø0.20
10-32 Mounting Holes
FIGURE 3.5
MD50 OUTLINE DRAWING

REV. D February 24, 2011 12 Manual Number 9017039
3.75
8.75
NOTE: Mounting adapter can be installed on either end of the unit.
FIGURE 3.6
MD50 MOUNTING ADAPTER

REV. D February 24, 2011 13 Manual Number 9017039
SECTION 4 OPERATION
4.1 ELECTRICAL PERFORMANCE
The MD50 series Static Inverter converts a direct current (DC) voltage input to a regulated 115 volt
alternating current (VAC) output. The output is controlled to a frequency of 60 Hertz and represents a
pure sine wave with minimal distortion. The unit is capable of providing 500 watts to power a variety of
aircraft accessories including laptops, personal electronics, onboard systems, and many others.
(See Section 1.2.1 for tolerance ranges)
The unit is designed as a two-stage, solid-state switch-mode power supply. The power transformation
utilizes a first-stage push-pull methodology followed by an H-bridge AC forming second stage. The
primary stage utilizes ‘current-mode’ control providing instantaneous load protection as an advantage
over legacy designs that incorporate ‘voltage-mode’ controllers. The alternating current is frequency
controlled using a crystal oscillator reference.
Figure 4.1 Total Harmonic Distortion Performance vs Load
Figure 4.2 Output Power Performance vs Temperature
0.00
0.50
1.00
1.50
2.00
2.50
0 200 400 600 800
THD%
outputpower(watts)
0
100
200
300
400
500
600
‐60 ‐20 20 60 100
outputpower(watts)
temperature(°C)

REV. D February 24, 2011 14 Manual Number 9017039
4.2 PROTECTIVE FEATURES
4.2.1 REMOTE ON/OFF
The MD50 series Static Inverter incorporates a remote on/off feature that allows the user to
enable or disable the output of the unit. By providing a ground on the appropriate pin (See
Table 3.3) the user, via a remote mounted switch or similar method, can enable the output
of the unit. The unit can be similarly disabled by removing the ground signal (open circuit) to
the same pin.
4.2.2 OVER-VOLTAGE
When the input voltage exceeds the operating range of the unit (See Section 1.2.1; absolute
maximum input of 37VDC) the unit senses an over-voltage condition and disables the output.
The unit will dynamically monitor the input voltage such that if the input returns to within the
normal operating range, the output will be enabled and allow the unit to operate normally.
4.2.3 UNDER-VOLTAGE
When the input voltage drops below the operating range of the unit (See Section 1.2.1;
absolute minimum input of 20VDC) the unit senses an under-voltage condition and disables
the output. The unit will dynamically monitor the input voltage such that if the input returns
to within the normal operating range, the output will be enabled and allow the unit to
operate normally.
4.2.4 OVER-TEMPERATURE
The MD50 incorporates an internal temperature sensing device that continually provides
monitoring and feedback to the control circuits. When the unit senses an internal condition
that exceeds maximum temperature ratings, the output is disabled. The internal cooling fans
will continue to operate and the unit output will be enabled when the temperature returns to
within acceptable limits. This over-temperature reset occurs automatically without external
intervention required.
4.2.5 SHORT CIRCUIT AND OVER-CURRENT
The MD50 is capable of surviving a short circuit or over-current event without permanent
damage or effect to long-term reliability. The unit can provide over its rated power output up
to 550 watts for up to 2 hours. The unit is also capable of supporting an overload condition
of 750 watts for 5 minutes with distortion of the sine wave and reduced voltage output.
The unit monitors on pulse-by-pulse scenario to determine a short circuit or over-current
situation. If detected, the output is limited by clipping the AC sine wave form, limiting the
power output. The unit will also produce an audible clicking noise, indicating that the power
output limit has been exceeded. When the short circuit or over-current event is removed, the
unit will return to normal operation.
4.2.6 TEMPERATURE REGULATED COOLING
The unit is equipped with two internal brushless DC fans for cooling to extend the power
range and long-term life. The fans are activated at a specified point determined by the
continuous monitoring of the internal temperature. The fans operate very quietly to reduce
the audible noise in any environment. The two fans provide independent redundancy for
protection of the unit in the event that one becomes inoperative.
The unit is also designed to provide 75% of the rated load continuously at temperatures up
to +40°C in the event that both fans become inoperable and no cooling is available.

REV. D February 24, 2011 15 Manual Number 9017039
SECTION 5 CONFORMANCE
5.1 CONTINUED AIRWORTHINESS STATEMENT
No periodic scheduled maintenance or calibration is necessary for continued airworthiness of the MD50
series Static Inverter. If the unit fails to perform to specifications, the unit must be removed and serviced by
Mid-Continent Instruments or their authorized designee.
5.2 ENVIRONMENTAL QUALIFICATION STATEMENT
NOMENCLATURE: Static Electrical Power Inverter
MODEL NUMBER: MD50-( ) TSO NUMBER: C73
MANUFACTURERS SPECIFICATIONS:
Minimum Performance Specifications: Test Specification (TS) 445, Test Data Sheet (TDS) 445
QUALIFICATION STANDARD: RTCA DO-160F
CONDITIONS SECTION DESCRIPTION OF TEST
Temperature and Altitude
Low Temperature
High Temperature
In-Flight Loss of Cooling
Decompression
Overpressure
4
4.5.1
4.5.2
4.5.5
4.6.2
4.6.3
Category F3(Y)
Operating Low Temp = -55C
Operating High Temp = +70C
Category Y = 300 minutes, +40C, 75%
Altitude = +55,000 ft
-15,000 ft
Temperature Variation 5 Category S2
Humidity 6 Category B
Operational Shock and
Crash Safety 7 Category B
Vibration 8 Category R, Curve C, C1
(RCC1)
Explosion 9 Category X
Waterproofness 10 Category X
Fluids 11 Category X
Sand and Dust 12 Category X
Fungus 13 Category X
Salt Spray 14 Category X
Magnetic Effect 15 Category Z
Power Input 16 Category X
Voltage Spike 17 Category X
Audio Frequency Conducted
Susceptibility 18 Category X
Induced Signal Susceptibility 19 Category X
Radio Frequency Susceptibility 20
Category X
Emission of Radio Freq Energy 21 Category B
Lightning Induced Transient
Susceptibility 22 Category X
Lightning Direct Effects 23 Category X
Icing 24 Category X
ESD 25 Category X
Flammability 26 Category X