Orbit AC/DC-1200 Series Use and care manual

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MNL107-900-000D
USER'S GUIDE AND
TECHNICAL REFERENCE
AC SOURCE
BEHLMAN MODEL AC/DC-1200 SERIES
FOR SERVICE ASSISTANCE
CONTACT BEHLMAN
CUSTOMER SERVICE DEPARTMENT
PHONE TOLL FREE 1-800-874-6727
OR WRITE
BEHLMAN
CUSTOMER SERVICE DEPARTMENT
80 CABOT COURT
HAUPPAUGE, NY 11788
PHONE: [phone]
FAX : [phone]
FOR SALES INFORMATION:
PHONE: [phone]
USA : [phone]
FAX : [phone]
SUBJECT TO CHANGE WITHOUT NOTICE
DATE: 04/04/2016 Revision: D

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MNL107-900-000D
SAFETY SUMMARY
The following safety precautions must be observed during all phases of
operation, service, and maintenance of this equipment. Failure to comply with
these precautions or with specific warnings elsewhere in the manual violates
safety standards associated with the design and intended use of this equipment.
This manual forms an integral part of the equipment and must be available to
operating personnel.
GROUND THE EQUIPMENT
This equipment may have high leakage current to chassis due to EMI filtering
requirements. To minimize shock hazard, the equipment chassis(s) must be connected
to an electrical safety ground. This equipment is supplied with a three conductor line
connection for single phase applications and/or a five wire connection for three phase
applications. Both types include an earth terminal intended for safety ground
connections. In addition, isolated installation sites may require neutral to earth
connections as per NEC section 250 (National Electrical Code). Refer installation to
licensed electrician or other qualified personnel.
DO NOT OPERATE IN EXPLOSIVE ATMOSPHERE
Do not operate the equipment in the presence of flammable gases or fumes. Operation
of any electrical instrument in such an environment constitutes a definite safety hazard.
KEEP AWAY FROM LIVE CIRCUITS
Operating personnel must not remove equipment covers. Component replacement and
internal adjustments must be made by qualified maintenance personnel. Do not replace
components with power applied. Under certain conditions, dangerous voltage may exist
even with the power removed. To avoid injuries, always disconnect power and
discharge circuits before touching them. During normal operation the operator does not
have access to internal hazardous voltages. However, depending on the user’s
application configuration, HIGH VOLTAGES HAZARDOUS TO HUMAN SAFETY may
be normally generated at the output terminals. The customer/user must insure that the
output power lines are labeled properly as to the safety hazard and that any inadvertent
contact is eliminated.
DO NOT SERVICE OR ADJUST ALONE
Do not attempt internal service or adjustment unless another person, capable of
rendering first aid and resuscitation is present.
DO NOT SUBSTITUTE PARTS OR MODIFY INSTRUMENT
Because of the danger of introducing additional hazards, do not install substitute parts
or perform any unauthorized modification to this equipment. Contact Behlman
Electronics for proper replacement parts and specific service information.

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MNL107-900-000D
DANGEROUS PROCEDURE WARNINGS !
Warnings will precede potentially dangerous procedures in this manual. Instructions
contained in the warning must be followed. Warnings will be preceded by the caution
symbol (above).
RISK OF ELECTRIC SHOCK
This symbol warns personnel of hazardous conditions due to the exposure of hazardous
voltage that can be lethal if contacted.
Neither Behlman Electronics, Hauppauge, NY, USA, nor any of the subsidiary sales
organizations can accept any responsibility for personnel, material or inconsequential
injury, loss or damage that may result from improper use of the equipment and/or
accessories provided.
For additional safety related technical information, contact the Behlman Electronics
sales department or local sales representative.
[email protected]

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MNL107-900-000D
CLAIM FOR DAMAGE IN SHIPMENT
Under the FOB factory terms of sale, ownership and responsibility are transferred to the customer when
the equipment leaves the factory. Each Behlman product is shipped from the factory in proper operating
condition.
Immediately upon receiving equipment, unpack and inspect it for evidence of damage incurred in
shipment. File a claim with the freight carrier if the equipment has been damaged in any way or it fails to
operate properly. Forward a copy of the damage claim report to Behlman. Include the model number,
serial number and date the shipment was received. Behlman will advise the disposition of the equipment
and will arrange for necessary repair or replacement.
RETURNING EQUIPMENT TO FACTORY
Do not return equipment to the factory without prior authorization from Behlman.
A RETURN MATERIAL AUTHORIZATION NUMBER (RMA) is required to return equipment.
This equipment, like all precision electronic equipment, is susceptible to shipping damage. It contains
heavy magnetic components as well as delicate electronic components.
If equipment is returned without prior authorization, the shipment will be refused, the customer being
liable for all shipping, handling and repair costs.
When packing for reshipment, use the original shock absorbent material and shipping container to
preclude damage to the equipment.
Insure that the return authorization numbers (RMA) is available on the container for identification.
SHIPPING INSTRUCTIONS
RACK MOUNTED UNITS
1) Box(es) must be double wall with minimum 350 lbs. bursting test.
2) Box(es) must provide for a minimum of 3 to 4 inches of clearance around sides, top and bottom of
unit.
3) When packing unit, utilize either a foam-in-place system or high density foam. Clearance
provided for above must be completely filled with foam.
FAILURE TO COMPLETELY SECURE UNIT IN BOX WILL ALLOW
MOVEMENT DURING SHIPPING, RESULTING IN DAMAGE.
4) Secure box(es) to pallet(s). This is necessary to insure proper handling and protection during
shipping.
5) Place the following warning label on box(es)
DO NOT STACK
6) Ship unit(s) using a freight cargo carrier; air or ground.
CABINET MOUNTED UNITS
Cabinet mounted units require that a special crate be used. The crate should be manufactured of plywood
(3/8" or thicker) and reinforced (using 1 x 3 or larger pine) on all edges. The unit must be firmly secured to
the crate’s base. The crate must be shock mounted to avoid damage during shipping. Detail drawings for
Behlman's crates are available upon request.

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MNL107-900-000D
WARRANTY CERTIFICATE
Behlman Electronics, Inc. warrants to the original purchaser, for a period of one (1) year from the
shipment from Behlman, each item to be free from defects in material and workmanship.
Behlman’s obligation and the Purchaser’s sole remedy for any breach or violation of this
agreement is limited to adjustments, repair or replacements for parts which have been promptly
reported by the Purchaser as having been in its opinion, defective and so found by Behlman upon
inspection. All replacement parts will become the property of Behlman on an exchange basis. This
warranty will not apply if such adjustment repair or parts replacement is required because accident,
neglect, misuse, failure of environmental controls, transportation damage or causes other than
normal use.
If during the warranty period a defect should impair the performance of the unit, Behlman agrees,
at its option, to repair or replace the unit or its defective components F.O.B. Behlman at 80 Cabot
Court, Hauppauge NY 11788 or at another Behlman service facility at Behlman’s option. To obtain
service under this warranty, the original Purchase shall notify Behlman at the above address or by
telephone at 631-435-0410 and provide information about the defect or impairment of
performance. Behlman with then supply the Purchaser a Return Material Authorization (RMA)
number. This number must be attached to the equipment sent back for warranty repair. Equipment
must be shipped back to Behlman prepaid. No collect shipments will be accepted.
Behlman shall be excused from supplying warranty service if the unit’s case has been opened or if
the unit has been subject to unauthorized repair. All service outside the scope of this warranty
shall be paid for by the Purchaser at Behlman’s rates in effect at the time of this repair. Behlman
will not perform any repairs outside of the warranty without written authorization by the Purchaser.
If the repair is a warranty repair, Behlman will ship the unit back to the Purchaser, by a method
determined solely by Behlman, prepaid. If the Purchaser requests, any other means of
transportation it shall be at the Purchaser’s expense.
The use of the equipment shall be under the Purchaser’s exclusive management and control. The
Purchaser will be responsible for assuring the proper installation, use, management and supervision
of the equipment. Behlman will not be liable for personal injury or property damage.
The forgoing warranties are in lieu of all other warranties, expressed or implied including without
limitation warranties of merchantability and fitness for purpose.
In no event shall Behlman be liable for loss of profits, loss of use, or any indirect, consequential or
incidental damages. Purchaser agrees that Behlman will not be liable for any damages caused by
the Purchaser’s failure to fulfill any of the Purchaser’s responsibilities set forth herein.

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MNL107-900-000D
TABLE OF CONTENTS
BEHLMAN AC SOURCE, MODEL ACDC-1200
SECTION
1.0 INTRODUCTION
1.1 Specifications
2.0 UNPACKING AND INSTALLATION
2.1 Unpacking
2.2 Installation / Wiring
2.3 Installation Considerations
3.0 OPERATION
3.1 Controls and Indicators
3.2 To Operate the Equipment
3.3 Shutdown Procedure
3.4 Operating Considerations
3.5 Alarm Contacts
3.6 DC Preferred Input Option
4.0 THEORY OF OPERATION
4.1 General
4.2 Detailed Theory
4.3 Reference Oscillator
4.4 Error Amplifier
4.5 Sine Weighted PWM
4.6 Output Section
4.7 Closing the Loop
4.8 Current Limit
4.9 Over temperature
4.10 Housekeeping Supplies
5.0 TROUBLESHOOTING AND MAINTENANCE
5.1 Troubleshooting
5.2 Maintenance
Appendix A Recommended spare parts list
Revision History
Reference Documents

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MNL107-900-000D
SECTION 1
INTRODUCTION
The Behlman model series AC/DC 1200 inverters provide conditioned AC power.
They may be powered from AC or DC input voltages that vary over a wide range. The
output from these models is an isolated fixed sine wave voltage regulated to better than
1 percent. When combined with user supplied batteries, these units can be configured
to provide a true online uninterruptable AC power supply. These units are available with
AC preferred (A1) or DC preferred (D1) options. These options allow the primary power
source to be either AC or DC. A set of alarm signal contacts are also provided to allow
integration into a user defined control and monitoring system.
To illustrate the operation of these models a simplified functional block diagram is
provided in figure 1-1 below. Both the DC to DC converter and AC output inverter are
based on High Frequency PWM switching techniques. This allows for small size and
High efficiency.
FIGURE 1-1

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MNL107-900-000D
1.1 SPECIFICATIONS
INPUT POWER
AC 120 VAC ±10% single phase, 47 to 63 Hz, 20 Amps max.
DC 48 VDC or 125 VDC ±20% (depending on model)
DC burden for 48V units = 40 Amps @ 38 VDC
(>2A quiescent)
DC burden for 125V units = 15 Amps @ 100 VDC
(>1A quiescent)
OUTPUT POWER
Voltage: 120 VAC ±5%, 60 Hz ±.01% (other frequencies available)
Current: 10 Amps max. (1200 watts) de-rated above 25°C.
Current Crest Factor: 3:1.
Power Factor: 100% of rated output into any power factor load.
Distortion: 5% maximum THD (measured at full resistive load).
Load Regulation: ±0.7% from no load to full load.
Line Regulation: ±0.1% for ±10% of line change.
Efficiency 80%
MECHANICAL
Dimensions: WIDTH: 17 in. (432mm), (19”standard. EIA rack panel),
LENGTH: 19in. (483mm)
HEIGHT: 5.5in. (144mm)
Weight: 60 lbs. (27kgm)
ENVIRONMENTAL
Operating
Temperature: -20°C to 55°C (32°F to 131°F).
Humidity: Up to 95% non-condensing.
EMI / RFI Designed for immunity to conducted and radiated sources.

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MNL107-900-000D
SECTION 2
UNPACKING AND INSTALLATION
2.1 UNPACKING
After unpacking the inverter (unit), carefully conduct a thorough inspection of controls, indicators,
and chassis. If the unit shows signs of damage, do not attempt to operate. File a damage claim
with the carrier responsible. Notify Behlman immediately.
2.2 INSTALLATION / WIRING
1) This unit is designed to be rack mounted in a standard EIA 19" cabinet but can be operated in
any location. It is preferable to operate in a location which will maintain air temperature of 0-55°C
around the ventilation ports. Therefore if the unit is to be rack mounted, it is recommended that
the enclosure be forced ventilated or air conditioned. Installation should insure that the side and
rear vents are unobstructed.
IMPORTANT NOTE:
The unit must have bottom support when mounting in a rack or cabinet. Do not attempt to mount
by front panels only. Chassis slides or mounting angles are available for this purpose. Consult
with the Behlman sales department.
2) Ensure that the line circuit breaker is in the OFF position before connecting input power.
3) Connect input/output power lines as follows:
WARNING
Ensure that input line and neutral are connected to proper AC input terminals. A protective
earth connection is required for operator safety and EMI filter return currents. Do not
operate without this connection.
a) INPUT POWER- Is connected to the appropriate terminals on the unit's rear panel. (See
figures 2-1 & 2- 2). The proper size of input wiring is determined by the wire length and
current to be carried. The following table lists suggested wire size for lengths up to 50
feet. Longer lengths should use larger diameter wire.
MODEL NUMBER AC INPUT WIRING DC INPUT WIRING
AC\DC1200-125 # 12 AWG up to 25 feet
# 10 AWG up to 50 feet #14 AWG up to 25 feet # 12 AWG up to 50 feet
AC\DC1200-48 # 12 AWG up to 25 feet
# 10 AWG up to 50 feet #10 AWG up to 25 feet # 8 AWG up to 50 feet
! CAUTION
Failure to use the proper wire size may result in erratic operation and may create a
fire Hazard.
b) OUTPUT POWER- Output power lines are connected to the rear panel NEMA 15R
receptacles (see figure 2-1). Note, any one receptacle can handle the full load current.
TB option units are provided with barrier type terminal blocks in place of the standard
outlets. These use #6-32 hardware and ring lugs are recommended.

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MNL107-900-000D
FIGURE 2-1 CONTROLS AND FEATURES AC/DC1200 SERIES
ITEM TYPE DESCRIPTION
1 INPUT BREAKER (s) Controls AC/DC input ON/OFF.
2 AC BYPASS FUSE Fuses AC after bypass relay.
3 LED INDICATORS
Green LEDs indicate “good” condition
for AC/DC in and inverter status.
4 AC OUTPUT (NEMA 15R shown) AC to load, option terminal block type
available.
5 AC INPUT TERMINALS
AC power applied via 6/32 screw
terminal block.
6 DC INPUT TERMINALS
DC power applied via 10/32 screw type
terminal block.
7 ALARM RELAY TERMINALS Dry relay contacts to signal faults in parallel with front panel LEDs. See
manual text.
BEHLMAN ACDC-1200-48
AC PRESENT
DC PRESENT
SYSTEM OK
AC OUTPUT
BYPASS FUSE
DC
AC
CAUTION
On-Line Uninterruptible Power Source
REAR PANEL
FRONT PANEL
1
2
3
4
5
6
7

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FIGURE 2-2 MECHANICAL OUTLINE AC/DC 1200 SERIES INVERTERS
BEHLMAN ACDC-1200-48
AC PRESENT
DC PRESENT
SYSTEM OK
AC OUTPUT
BYPASS FUSE
DC
AC
CAUTION
On-Line Uninterruptible Power Source
MECHANICAL OUTLINE

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FIGURE 2-3 RECOMMENDED TYPICAL INSTALLATION

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MNL107-900-000D
2.3 INSTALLATION CONSIDERATIONS
Figure 2-3 illustrates typical wiring to and from the AC/DC 1200. When the load is running from
the inverter (not-by-passed) the output circuit is completely floating with respect to the AC input,
DC input and earth connection. This arrangement provides the user with flexibility in regards to
the output circuit reference point. When in the bypass mode, the inverter is disabled and the AC
input is routed directly from the AC input terminal to the output terminals (refer to Figure 1-1 in
section 1). This will place the output circuit at the same reference as the AC line. In North
America the neutral terminal is defined as the “grounded conductor” and is bonded to the
earth connection at the service entrance. This is defined in the Nation Electrical Code (NEC)
section 250 regarding bonding and protective (a.k.a. safety) earth connections.
The NEC considers AC sources that are Isolated from the AC supply as “separately derived
sources”. Stand alone back-up generators, some UPSs, and battery powered inverters fall into
this category. If this equipment is to be installed in a building or vehicle that must meet the NEC,
then grounding of the output circuit will be required. This can be accomplished by the connection
suggested in the figure 2-4 below. For units with a terminal block output option this is easy to add.
Units with NEMA plug output may require adding an external outlet box to make this connection.
If specified at time of order, units can be modified by Behlman to provide this connection. A
connection could be added from AC output low terminal to earth, however this would violate NEC
bonding rules when the unit is in the bypass mode. If this concept is not understood consultation
with a licensed electrician is highly recommended.
FIGURE 2-4

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MNL107-900-000D
SECTION 3
OPERATION
!WARNING
This equipment involves the use of voltages and currents that can be hazardous under
normal operating conditions. Only qualified personnel should be allowed to operate or
service it. All covers and guards must always be in place during operation. A protective
earth connection must be used.
3.1 CONTROLS AND INDICATORS (refer to fig 2-1.)
1. INPUT POWER BREAKER: Dual circuit breaker interrupts AC and DC input power in the
event of and internal fault. If breaker trips, unit will enter the line By-pass mode which will
route the input AC line to the output terminals. (NOTE: 48 VDC units have separate AC
& DC breakers.)
2. BY-PASS FUSE: protects the AC line and unit wiring in the event of an output overload
while in bypass mode. Fuse rating is 15 amps / 250 VAC. Replace fuse with same type
and rating only.
3. STATUS INDICATING LEDS: operation as follows:
a.) DC PRESENT: Indicates green when DC input is within operating range of +/- 20%
b.) SYSTEM OK: indicates green when back-up inverter and internal supplies are
functional.
c.) AC OUTPUT: indicates green when output is supplied by Aon-line@inverter
d.) AC PRESENT: indicates green when AC line input is within operating range.
4. ALARM CONTACTS: “Dry” type contacts will open in conjunction with the front panel
status indicators. If the status indicator turns off, the appropriate alarm contacts will open.
See section on alarm contacts in this manual for further information.
5. AC INPUT TERMINAL BLOCK: facilitates connection of line input (use of # 8 ring lug
recommended) connect as marked. “HI” terminal to line “LO” terminal to neutral and
“GND” terminal to safety earth (protective earth as defined by IEC-61010-1).
6. DC IN TERMINAL BLOCK: facilitates connection of DC input. Note: 125 VDC inputs are
not polarity sensitive and may have +/- wires reversed.
! CAUTION
48 volt units require +/- polarity to be connected as indicated. Failure to do so will trip the
input breaker and may cause damage to the equipment.
7. OUTPUT CONNECTIONS: typically supplied as NEMA 15R type connectors. Customer
specified connectors or terminal blocks may also be provided as an option. Check model
and part number on units rating label. Special units will have a unique four digit suffix to
indicate any special configuration.

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MNL107-900-000D
3.2 TO OPERATE THE EQUIPMENT
1) Ensure that front panel circuit breaker(s) is set to OFF.
2) Connect a suitable load to NEMA 5-15R receptacles (or other optional output connector).
3) Turn on AC INPUT Power.
4) Turn on DC INPUT Power.
5) Set the front panel circuit breaker(s) to ON (cooling fans noise should become evident). If
desired, the output voltage and frequency can be confirmed by connecting a true RMS voltmeter
such as a Fluke model 87 across the output terminals or load.
3.3 SHUTDOWN PROCEDURE
1) Set front panel circuit breaker(s) to OFF.
3.4 OPERATING CONSIDERATIONS
The Behlman ACDC1200 series of power supplies are solid-state electronic devices. As such
they cannot supply infinite current and are therefore electronically protected from overloads.
Certain loads will draw “in rush” or start up currents that may be 10 times higher than their normal
run current. Although the design of the ACDC1200 allows for several hundred milliseconds worth
of “start” current, not all loads will behave the same. In many cases, a poorly designed power
supply or motor with no in-rush current limiting may trip the protective circuits of the model
ACDC1200. This may show up as a dip in voltage during start up (current limit) or an immediate
transfer to by-pass mode as the load is energized. The later indicates the back-up inverter has
entered a protection mode and power must be recycled to restore operation.
If problems are encountered energizing a particular load, the “in-rush” current of the load should
be determined before the problem is associated with the model AC/DC 1200. In the event of
problems see the trouble-shooting portion of this document. The Behlman engineering
department is also available to help provide a solution. Contact the factory for additional
information.
3.5 ALARM CONTACTS
Rear panel alarm contacts are rated at 0.6 amps @ 125 VAC or 30 VDC. These contacts are
completely isolated from the AC and DC inputs. The diagram below illustrates the contact
arrangement.
Figure 3-1 alarm contact configuration

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MNL107-900-000D
3.6 OPERATIONAL CONSIDERATION FOR DC PREFERRED OPTION
The standard model AC / DC 1200 is designed to operate primarily from the AC line. If the AC
line fails, operation from the DC supply (Batteries) is automatic. When the AC is recovered, the
unit will again automatically resume operation from the line. These units are considered to be “AC
preferred”. The D1 option provides the opposite function. When both the AC and DC sources are
available, the D1 unit will operate primarily from the DC power. When the DC is removed the unit
will automatically switch to AC line operation. In both cases, if the inverter were to fail, the AC line
will be “by-passed” directly to the output terminals.
Operating Considerations:
Because this operates primarily from the DC source (most likely batteries) it should be noted that
current (and power) will always be drawn from the source even when no load is connected to the
unit. There are certain fixed minimum losses associated with DC operation that determine this
current. For a 48Vdc unit this quiescent current is about 2 Amps. The 125Vdc input requires less
than 1 Amp.
Switching from DC to AC power is accomplished by a relay with a transition time of between 2
and 10mSec. If the unit is heavily loaded, a dip in the output voltage during switch over may be
encountered. When selecting components to design a back-up power system, use devices with
“hold up” times greater than 10mSec whenever possible. This is not an issue with AC preferred
units.
To determine which version is being used, look at the rating label affixed to the right side panel of
the unit. DC preferred units will be designated D1.
The internal impedance of the DC source will affect the transient capability of these units.

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MNL107-900-000D
SECTION 4
THEORY OF OPERATION
4.1 GENERAL
The ACDC1200 series (unit) represent a rugged, high performance AC UPS. The unit operates
from a 120 VAC or a 48 VDC, or 125 VDC INPUT based on the model selected.
4.2 DETAILED THEORY
The AC input voltage is rectified by employing a voltage doubling circuit consisting of a half wave
rectifier and two banks of input capacitors. Voltages approximating the positive and negative
peaks of the input (+/-160 VDC) are stored on the capacitor banks that are centered about the
input neutral. The two rectified voltages provide the necessary DC power. The EMI filter at the
input, limits the conduction of electromagnetic interference back on to the line.
When operating from DC, the DC/DC converter takes a battery input of 125VDC (or 48V on some
models) and converts it to a dual +/- 150Vdc (approx). The DC to DC circuit is based on a
MOSFET driven, full bridge type topology. The complete circuit is housed on assembly # 107-
915-00X. This circuit also provides pre-regulation and battery isolation. The output of the DC to
DC converter is diode “or-ed” with the DC from the rectifier circuit and both are applied to the
output inverter/amplifier.
The DC/AC or inverter portion of the unit uses a high frequency PWM technique to converts the
DC buss back to AC. The pulse width modulation (PWM) design of this switching unit generates a
high frequency square wave of variable duty cycle. By varying the duty cycle from 8% to 92% a
net DC component is created that ranges between the positive and negative DC buses. A two
stage LC low-pass filter averages the PWM to produce the DC component. If the input to this
circuit is a sine wave, than an AC output is produced. This stage can be said to amplify the sine
wave. It is considered a class “D” amplifier. The amplifier produces about 90Vrms which is
applied to an isolated step-up transformer to produce the required 120Vac on the output.
4.3 REFERENCE OSCILLATOR
The reference oscillator and associated circuitry are shown in figure 4-1. The reference oscillator
produces a sine wave in which frequency is controlled a crystal derived clock. The amplitude is
controlled by a precision dc reference voltage. The output voltage of the inverter is sampled and
compared to the reference voltage. Any error is amplified and used to control the oscillator
amplitude. This action corrects for output voltage variation due to line and load changes.
4.4 ERROR AMPLIFIER
The error amplifier is configured as an integrator that algebraically sums the reference sine wave
with the unfiltered PWM output to produce the instantaneously required signal to the PWM to
reproduce the desired sine wave.
4.5 SINE WEIGHTED PWM
The output of the error amplifier is summed with a high frequency (20 kHz) triangular wave to
produce a PWM “sine weighted” function. The resulting output is a pulse train with it’s duty cycle
modulated by the sine wave. These signals are applied to the insulated gate bipolar transistor
(IGBT) drivers for application to the IGBT power switches.
4.6 OUTPUT SECTION
The sine weighted PWM power output of the IGBT is filtered by a double LC filter network to
remove the 20KHz switching frequency. This action leaves an amplified version of the modulating
signal (sine wave). A current sense transformer is used to monitor the output current. The signal
from the transformer is applied to the over-current protective circuits.

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FIGURE 4-1 BLOCK DIAGRAM

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MNL107-900-000D
4.7 CLOSING THE LOOP
In order to provide a clean output with very good regulation, two feedback loops are used. One
feedback loop is a fast loop that takes the IGBT output and closes the loop to the error amplifier.
This loop corrects for switching effects on a pulse-by-pulse basis. The second feedback loop
corrects for regulation. It is a slow loop that takes the output at the output transformer and
converts it from RMS to DC to compare to and modify the reference. Current feedback from the
current sense transformer is used in another loop to effectively limit the output current. The output
of this transformer is converted from RMS to DC and is used to reduce the reference once a
preset limit is reached. The later action causes that output voltage to reduce if the current
attempts to increase further.
4.8 CURRENT LIMIT
There are two distinct current limits:
Overload- The overload limit uses the RMS/DC converter output of the output current sense
transformer. When the DC voltage exceeds 2.5V (approximately 120% of nominal), the reference
gets overridden and the output goes into constant current mode. The voltage decreases to force
the unit to hold the current at 120% of nominal. The RMS/DC converter has a filter with an
equivalent 200 millisecond delay. This means that as long as the RMS output current does not
exceed 120% of nominal for more than 200 milliseconds, the output will not be affected.
Short Circuit Protection- Short circuit protection is a circuit that protects the unit and load from
short circuits of greater than 300% of nominal current. The IGBT drivers have internal circuitry to
sense de-saturation of the IGBT. De-saturation is caused by excessive output current. The driver
over-current outputs are used to set a latch. The latch is used to inhibit the PWM signal to the
IGBT drivers, which immediately disables the output inverter. Power must be cycled to reset this
type of overload.
Note: A “constant current” overload may cause the “SYSTEM” status light to flash or grow dim.
A short circuit overload will cause the “SYSTEM” to go off and stay off until reset.
4.9 OVER TEMPERATURE
The unit contains a temperature sensor that is located on the IGBT heat sink. If an excessive
temperature is sensed, the sensor output which is “OR-ed” with the over current latch signal,
turns off the output until the temperature has decreased to an acceptable limit.
4.10 HOUSEKEEPING SUPPLIES
Three small, fly-back based DC/DC switching power supplies generate all the DC voltages
needed to run the internal circuits. The DC to DC converter assembly has a small Ahousekeeper@
that runs from the input DC and provides control power to the converter. Another low power
DC/DC convertor provides standby power for the front panel control board (107-920 -00X). This
converter takes power either from the AC or DC inputs to supply monitoring circuits at times.
An additional 30W fly-back supply located on the output inverter board (107-752-000) handles the
rest of the operating power including the cooling fan. This supply runs from the bulk 150Vdc
power.

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MNL107-900-000D
SECTION 5
TROUBLE SHOOTING
5.1 TROUBLESHOOTING
In the event problems are encountered during the installation and operation of the inverter refer to
the chart below before assuming the inverter is at fault. If it is determined the fault is with the
inverter, contact Behlman Electronics for service information.
SYMPTOM POSSIBLE CAUSE ACTION
Low or no output status LED off.
AC output LED may be off.
Output overloaded Check load current. Disconnect
load and recheck output voltage
using TRUE RMS meter.
Recycle power.
Erratic operation Input voltage fluctuating Monitor voltage at the DC input
terminals of the inverter. Make
sure DC is within specifications.
No AC input alarm
AC input LED off.
AC - Bypass fuse blown Check fuse. Measure AC input
at rear panel.
Output distorted High peak load current or non-
linear load. Reduce loading if distortion is objectionable. Check load
current waveform.
DC breaker repeatedly trips DC polarity reversed or internal
fault in inverter. Check polarity, if ok the unit may have an internal fault.
Return for service.
SPECIAL CONSIDERATION FOR MOTORS
Loads that contain motors may present a special problem due to a mechanical load being
present.The start-up (a.k.a. Locked rotor current) for these devices may be much higher than
expected. These currents may also last from several cycle of the AC waveform to several
seconds. Motor start current “profiles” must be understood to prevent overloading the AC/DC
1200
5.2 MAINTENANCE
! WARNING
Service of this device requires specialized equipment and trained personnel. There are no
internal user serviceable parts. Removing the covers will expose individuals to hazardous
voltages. Refer service to qualified personnel only!
If the unit is to be supplied from batteries, the condition of the batteries will have a significant
effect on the operation of the unit. Poorly maintained batteries can cause the unit malfunction
when heavily loaded. If this device is to be used as part of a back-up power system a battery
maintenance schedule should be discussed with the battery manufacturer. Battery condition can
deteriorate quickly without proper maintenance. Behlman does not provide batteries for these
units. When performing battery maintenance, check and tighten all wire connections.