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1.0 SCOPE
1.1 The System
This specification
describes a single phase, on-line/off-line solid state DC to AC inverter
system. The inverter can operate in conjunction with the existing building
electrical system or DC power supply to provide power conditioning, back-up
power protection and distribution for electronic equipment loads. The
system consists of an inverter module that could encompass a static bypass
switch and LCD display as an option, maintenance bypass module (receiver
cabinet) and synchronizing circuitry as described herein.
2.0 APPLICABLE
STANDARDS AND AGENCY APPROVAL
2.1 The inverter meets
the requirements of the following standards:
· UL 1950 Listed
· UL Canada (cUL) listed
· EN60950, TUV
· CISPR22-1996
· FCC rules and regulations of Part 15, subpart J, class "A"
requirements for radiated and conducted emissions.
· IEC801-4 level 2/5 standards for immunity to fast transient and
surge voltages.
· IEC 801-2/3/6 and Bellcore TR-NWT-1089 standards for immunity
to radiated and conducted noise.
2.2 The inverter will be designed in accordance with the applicable sections
of the documents published by:
· National Fire Protection Association (NFPAA)/National Electric
Code (NEC).
· National Electrical Manufacturer's Association (NEMA).
· Bellcore's latest revision of TR-NWT-000063.
3.0 SYSTEM DESCRIPTION AND OPERATION
3.1 Inverter
The inverter output will be derived from a Pulse Width Modulation (PWM)
type inverter design. The inverter operates at a very high frequency (approx.
20KHz) and uses current mode loop control for excellent transient response
to load changes. The inverter shall incorporate a microprocessor for monitoring
and control. The microprocessor shall provide digitized phase locked loop
control, tolerance compensation control that eliminates hardware or potentiometer
calibrations and control of output parameters, sinusoidal reference, serial
port and monitoring of input and output AC/DC parameters.
3.2 On-line
The inverter can operate in either the on-line or off-line modes. The
on-line mode is defined as allowing the load to be powered at all times
from the inverter. The inverter is powered from the DC source. A loss
or over-voltage to the DC source will cause a transfer from inverter to
bypass in less than 2msec, if bypass exists. Without bypass, the inverter
will drop the load.
3.3 Off-line
The off-line mode is defined as allowing the load to be powered at all
times from the utility power source through the static transfer switch.
In case of a utility outage, the load will be transferred to the inverter
with less than 2msec interruption.
3.4 DC to AC Isolation
DC input will be completely floating (isolated) with respect to connections
to both chassis ground and AC input or output. This will be compatible
with the telephone Central Office requirements.
3.5 Automatic/Manual
Restart
For on-line mode, re-starting of the inverter after a transfer due to
loss of input DC voltage or over voltage can be either automatic or manual
(selectable). The inverter is factory-set for automatic re-start.
3.6 Over-voltage/Under-voltage
In the 48VDC system, if the DC input voltage exceeds 59 VDC, or if it
drops below 40 VDC, the inverter shall automatically shut down and transfer
to bypass (if available) and an alarm will be activated.
3.7 Over-Temperature
The inverter over-temperature warning alarm will be activated at 75 °C.
At 85 °C, the inverter will shut down to protect the system from major
catastrophic damage. The unit will then transfer to bypass.
4.0 STATIC BYPASS (OPTIONAL)
The static bypass
transfer switch will be a solid-state (back to back SCR), rated for continuous
duty and will operate under the following conditions:
4.1 On-line: If the
on-line mode has been selected, the inverter supplies the load. If the
static switch option is provided and the inverter fails, then transfer
to bypass shall be transparent; that is, no break in the output voltage
greater than 3 msec.
4.2 Off-line: If
the off-line mode has been selected and static bypass is installed, the
unit will transfer from utility power to inverter when the AC input voltage
is below +10%, -15% of the nominal value. Transfer shall be transparent;
that is, no break in output voltage greater than 3 msec.
· The unit will transfer from inverter back to the utility power
source when the AC input voltage is below 10% of the nominal value.
· The unit will transfer to inverter if the utility frequency is
out of tolerance by ±3Hz; the recovery is at ±2.5Hz.
· The unit will transfer from utility back to inverter when the
utility frequency changes greater than 1Hz/1 sec.
NOTE: Transfer from
inverter to line shall be delayed for a minimum of 10 seconds to insure
that the line has stabilized and the inverter has achieved phase lock
to the utility.
5.0 MAINTENANCE
BYPASS
An automatic make
before break maintenance bypass switch will be provided to isolate the
inverter module from receiver cabinet for maintenance. This will allow
the inverter module to be removed or replaced without affecting load operation.
The maintenance bypass switch is a 20 ampere (for 1kVA) relay located
on the AC EMI filtered circuit board. Please refer to single line diagram,
Fig. 1.1.
Figure 1.1: Single
line diagram (with static switch option).
6.0 INVERTER REQUIREMENTS
AND PERFORMANCE CHARACTERISTICS
6.1 Ratings
Power-Invert S3 provides
pure Sine Wave output with the following kVA ratings:
500 VA/420 W
1 kVA/840 W
6.2 Input Requirements
6.2.1 Voltage: -48
VDC Nominal (-42 to -57 VDC operating range).
6.2.2 500VA at -48VDC,
the input current is 11 Amps (420 W output).
1kVA at -48VDC, the input current is 22 Amps (840 W output).
6.2.3 EMI Filtering:
The input to the unit will have an EMI filter to eliminate conducted common
and differential mode noise on the AC and DC input lines. The filter will
insure that the conducted and radiated emissions meet the FCC, part 15,
subpart J, class "A" requirements and CISPRE22-1996, class "A".
6.2.3 DC Inrush Current
Limiting: Limits DC inrush current, thereby eliminating the requirement
for over-sizing input breakers or slow blow fuses.
6.2.4 Input Filtering:
An input filter shall be provided as part of the inverter to prevent transmission
of switching transients to the input battery. The input noise at the terminal
of a floated 240 AH lead-calcium battery with a 50-foot loop, as indicated
by a transmission impairment measuring set terminated with 600 ohms on
its input, shall not exceed 30 dBrnc for the 500VA and 1000VA inverters.
6.3 Output Characteristics
6.3.1 Output voltage:
100, 110, 115, 120, 200, 220, 230 or 240 VAC (selectable).
6.3.2 Line Regulation:
±1% maximum for line variation between low line and high line at
any load between no load to rated load.
6.3.3 Load Regulation:
±1% maximum for load variation between no load and full load at
nominal line.
6.3.4 Voltage Transient
Response: +10, -50% of peak value of rated output RMS voltage for 100%
step load change with recovery to 1% of nominal value within 1 millisecond.
6.3.5 Voltage Distortion:
Maximum 2% Total Harmonic Distortion (THD) when the inverter is connected
to 100% linear loads.
6.3.6 Non-Linear Load
Capability: Output voltage Total Harmonic Distortion (THD) will be less
than 3% when connected to a 100% non-linear load with a current crest
factor not to exceed 3:1.
6.3.7 Frequency: Frequency
shall be 50Hz or 60Hz, customer selectable. 50/60 Hz ±3Hz synchronized
to bypass (utility). 50/60 Hz ±.01% free running.
6.3.8 Power Factor:
KVA rating available over a power factor range of 0.6 to 0.84 lagging
or 0.6 to 0.84 leading over rated DC input voltage range. Crest factor
up to 3:1 for non-linear loads within rated VA/Watt rating.
6.3.9 Overload Capability;
-42Vdc to -57Vdc:
Up to 125% rated VA/Watts continuous (500VA, 1kVA)
120% to 150% - 1800 cycles
150% to 220% - 24 cycles
220% to 300% - 4 cycles
6.3.10 Efficiency:
-48 VDC input, 83% typical (500VA and 1kVA); On-line, 97% maximum; Off-line.
6.4 Environmental
Conditions
6.4.1 Ambient Temperature:
Operating, -10 ° to 50 °C, non-operating, -40 ° to +75 °C.
6.4.2 Relative humidity
(operating and storage): 0 to 95% non-condensation.
6.4.3 Acoustical Noise:
less than 55dBA @ 4 feet. (500VA and 1kVA)
6.4.4 Operating altitude
shall be from 200 feet below sea level to 10,000 feet above sea level.
Derate maximum ambient of 50 °C by 3 °C per 1000 feet of altitude
above 3300 feet (30 °C maximum at 10,000 feet).
6.4.5 Shipping altitude shall be 200feet below to 30,000 feet above sea
level.
7.0 MICROPROCESSOR
CONTROLLED LOGIC AND ALARMS
The inverter system
shall include an Intel microprocessor for control and monitoring.
7.1 Microprocessor
Control
The microprocessor provides complete control over those operations of
the static and maintenance bypass switches, inverter connect relay, battery
booster enable, inverter sine wave reference, inverter enable, LED (tri-color)
display, LCD display and alarm functions.
7.2 Front panel controls
& indicators on the inverter shall include the following:
7.2.1 On/Off DC circuit
breaker to activate/deactivate inverter.
7.2.2 Optional Measurement/Status
display (LCD):
Inverter models will have an integrated 20 character, 2 Line backlit LCD
that provides measurements and status. When this option is installed,
a "scroll" switch will be located next to the LCD display so
that the operator can scroll through the menu to determine the status
of the system. Readouts of voltages, current, load watts, load percentage
and frequency are available.
7.2.3 Standard inverter
models (with 2 tri-color LED's):
Two tri-color LEDs are mounted on the front panel of the inverter module.
The color of the LEDs will indicate the mode and status of the inverter
system. One LED is labeled "BYPASS", the other "INVERTER".
If the inverter system is set up for "OFF-LINE" mode, the "BYPASS
LED" will glow continuously GREEN and the "INVERTER LED"
will blink GREEN.
If the inverter system is set up for "ON-LINE" mode, the "INVERTER
LED" will glow continuously GREEN and the "BYPASS LED"
will blink GREEN.
a. BYPASS LED color:
GREEN Utility voltage
and frequency are within tolerance.
YELLOW WARNING! Utility voltage or frequency is out of tolerance and in
an undesirable range.
RED ALERT! BYPASS mechanism is abnormal or failed. Utility voltage or
frequency is dangerously low or high.
NOT LIT Bypass mechanism not available.
b. INVERTER LED color
GREEN Inverter is
on, no warnings or faults.
YELLOW WARNING! Minor or severe inverter overload. Input DC is out of
tolerance, thermal warning.
RED ALERT! Inverter not operating. Stopped for:
1. Inverter failure
2. Short circuit
3. Inverter thermal fault
4. Input DC is out of tolerance and dangerously low or high.
7.3 Internal switch
controls accessible to the installer:
· Voltage selection is 100, 110, 115, 120, 200, 220, 230 and 240
VAC (selectable).
· Frequency selection of 50Hz or 60Hz (selectable).
· Selectable automatic or manual restart from loss of input DC
voltage.
· Source select switch for selection of AC bypass (Off-line) or
on-line operation.
7.6 System Parameters
Monitored
The visual display shall show the following system parameters;
· Utility voltage (if bypass available)
· Utility frequency (if bypass available)
· Load (output) Voltage
· Load (output) frequency
· Load (output) Current
· Load (output) watts
· Percent Load
· Battery DC voltage
· Battery current
· Heat sink temperature
8.0 COMMUNICATION
FEATURE
8.1 Remote Alarms
Remote alarms shall be made available at the rear of the receiver cabinet
and accessible by the installer. A terminal block that includes three
form "C" relays (with static switch models), 1 form "C"
(without static switch models). The three alarm relays are identified
as:
1. Utility Failure Alarm
2. Minor Alarm
3. Major Alarm
8.1.1 Utility Alarm
A utility alarm will occur when there is no AC power present or it is
below 15% of the nominal voltage.
8.1.2 Minor Alarm
A minor alarm will occur for any of the following:
a. Short circuit or overload conditions on the inverter output or static
switch.
b. Any thermal warning or fault.
c. Input DC loss.
d. Static switch failure.
e. Four (4) transfers to bypass within four minutes (on-line mode).
8.1.3 Major Alarm
A major alarm will occur when the load is not powered by the inverter
or utility AC (static transfer switch or maintenance bypass relay).
8.2 Dry Contacts
Relay alarm contacts for the inverter module shall be rated 2 Amps for
120/240 VAC, 25 to 125 VDC.
9.0 SINGLE INVERTER
CONFIGURATION:
In this configuration, a single inverter will receive one AC and one DC
input, and provide a single AC output.
10 CASCADE REDUNDANT
CONFIGURATION
In this configuration, two inverters are wired in an active/stand-by mode.
Each inverter will receive one DC input. No AC input will be used. The
active inverter is working in the inversion mode and its AC output is
providing the AC input for the stand-by inverter. The stand-by inverter
is in by-pass mode and simply letting the AC source through to the load.
If the active inverter fails, the stand-by inverter will switch to inversion
mode and provide the required AC output.
11 MECHANICAL DESIGN
11.1 Inverter Unit
The inverter consists of two sections, an inverter module and a receiver
cabinet. The inverter unit can be mounted in a 19", 23" or 25"
rack. The inverter unit is designed to blend into a modern telephone central
office or a computer room environment. Dimensions are as follows:
POWER RATING DIMENSIONS
(H x D x W, In/cm) WEIGHT (lb./Kg)
500VA 3.5/8.9 x 17/43.2 x 19/48.26 34/15.4
1kVA 3.5/8.9 x 17/43.2 x 19/48.26 34/15.4
11.1.1 Receiver Cabinet:
The receiver cabinet consists of two side rails and a back plane section.
L shaped brackets are used to mount the receiver cabinet to a 19",
23" or 25" rack. The back plane of the receiver cabinet contains
wiring terminal blocks for the following:
· AC input voltage
· AC output voltage
· DC input voltage
· Alarm signals
When the receiver cabinet is mounted to the rack, the input, output and
alarm wiring can be permanently installed.
The back plane of
the receiver cabinet also contains the following:
· Maintenance bypass relay
· Utility alarm relay
· Minor alarm relay
· Input AC EMI filter
· Output AC EMI filter
· Input DC EMI filter
When the receiver cabinet is mounted and wired, utility power may be applied
and will power the load through the maintenance bypass relay. The maintenance
bypass relay is normally closed and will connect the utility AC input
directly to the AC output terminals. This enables the inverter module
to be easily slid into or out of the receiver cabinet rails without interruption
of power to the load.
11.1.2 Inverter Module:
The inverter module is designed to easily slide into or out of the receiver
cabinet without interruption of power to the load. The inverter module
contains all of the electronics necessary to provide automatic power transfer
to bypass mode upon overload or inverter failure, namely:
· Static switch bypass assembly
· Inverter power DC to AC assembly
· Microprocessor control assembly
· LCD assembly
11.2 Ventilation
The inverter unit is designed with an internal 24 VDC fan for forced air-cooling.
Air inlets are provided in the front of the inverter unit. Air exhaust
will be from the top, bottom and sides of the rear portion of the unit.
Full load heat rejection is as follows:
500VA @ -48VDC is 315 BTU/hr
1kVA @ -48VDC is 587 BTU/hr
Recommended air clearance distances for optimum cooling:
· .25" top and bottom
· 1.5" front, back and sides.
12.0 DOCUMENTATION
The manufacturer will
furnish the owner an instruction manual covering the installation, operation
and maintenance of the inverter.
13.0 WARRANTY
The inverter will
be covered by a full parts and labor warranty from the manufacturer. The
warranty period will be for twelve (12) months from date of installation
or acceptance by customer or eighteen (18) months from date of shipment
from the manufacturer, whichever occurs first.
14.0 APPROVED MANUFACTURER
The specified equipment
will be manufactured by MGE UPS SYSTEMS or approved equal.
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MGE UPS SYSTEMS |
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North America
