IEC 88528-11:2004

INTERNATIONAL IEC
STANDARD 88528-11
First edition
2004-03
Reciprocating internal combustion engine driven
alternating current generating sets –
Part 11:
Rotary uninterruptible power systems –
Performance requirements and test methods
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INTERNATIONAL IEC
STANDARD 88528-11
First edition
2004-03
Reciprocating internal combustion engine driven
alternating current generating sets –
Part 11:
Rotary uninterruptible power systems –
Performance requirements and test methods
 IEC 2004
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any
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– 2 – 88528-11  IEC:2004(E)
-
CONTENTS
FOREWORD.5

1 Scope.7
2 Normative references.7
3 Terms and definitions .8
3.1 General.8
3.2 Performance of systems and components .9
3.3 Specified values.10
3.4 Input values.11
3.5 Output values.12
4 Symbols and abbreviations.12
5 Selection criteria.12
6 General description.13
6.1 Rotary UPS.13
6.2 Types of rotary UPS .13
6.2.1 Series connected rotary UPS.13
6.2.2 Line interactive rotary UPS .14
6.3 Parallel operation of a rotary UPS installation.15
6.3.1 General.15
6.3.2 Parallel operation.15
6.3.3 Redundant operation.15
6.4 Power system changeover with rotary UPS installations (bypass).16
6.5 Enclosure protection.16
7 Modes of operation.16
7.1 Power conditioning mode .17
7.2 Independent mode.17
7.3 Bypass mode.18
7.4 Off mode.18
7.5 Transitions.18
7.5.1 Transition 1, starting the system with mains voltage present.18
7.5.2 Transition 2, start-up without mains voltage (black start) .18
7.5.3 Transition 3, disconnect from grid.19
7.5.4 Transition 4, connect to grid .19
7.5.5 Transition 6, transfer.19
7.5.6 Transition 7, 8, retransfer .19
8 Service conditions .19
8.1 Normal service conditions .19
8.2 Operation at extended ambient.19
8.2.1 Ambient service temperature.19
8.2.2 Ambient storage and transportation conditions .19
8.3 Engines.20
8.4 Rotating electrical machines.20
8.5 Control logic.20

88528-11  IEC:2004(E) – 3 –
9 Electrical service conditions and performance .20
9.1 General – all rotary UPS.20
9.2 Performance.21
10 Manufacturer technical declarations .22
10.1 General.22
10.2 Purchaser specification guidelines.22
10.2.1 Type of rotary UPS, additional features, and system requirements .23
10.2.2 Rotary UPS input.23
10.2.3 Load to be supplied from a rotary UPS .23
10.2.4 Rotary UPS output.24
10.2.5 Battery (where applicable) .24
10.2.6 General application requirements and special service conditions.25
10.2.7 Multi-module system configurations .25
10.2.8 Electromagnetic compatibility.26
11 Testing.27
11.1 Static output voltage and frequency deviations.27
11.2 Dynamic output voltage and frequency deviations .28
11.3 Input current characteristics .28
11.4 Measurement of filter properties .28
11.4.1 From mains to output.28
11.4.2 From output to mains.30
11.5 System performance.30
11.5.1 Efficiency.30
11.5.2 Stored energy times .30
11.5.3 Multi-module rotary UPS performance .30
11.6 Black start test.31
11.7 Environmental tests.31
11.8 Audible noise.31
11.9 Testing.31
12 Maintenance and product marking .33
12.1 Nameplate markings.33
12.2 Label requirements.34
12.3 Name plate marker.34
12.4 Decals – labelling .35
12.4.1 Safety instructions and documentation .35
12.5 Maintenance.35

Annex A (informative) Typical energy storage devices .36
Annex B (normative) Reference non-linear load – Single-phase.40
Annex C (normative) Reference non-linear load – Three-phase .42
Annex D (normative) Input mains failure – Test method .43
Annex E (informative) Types of uninterruptible power systems (UPS) configurations .44

Figure 1 – Types of UPS systems .13
Figure 2 – Typical example series connected rotary UPS.13
Figure 3 – Typical example of a line interactive rotary UPS.14
Figure 4 – Parallel operation of a rotary UPS .15

– 4 – 88528-11  IEC:2004(E)
-
Figure 5 – Bypass operation .16
Figure 6 – Illustration of rotary UPS operation .17
Figure 7 – Operating modes.18
Figure 8 – Surge test .29
Figure 9 – Warning label.34
Figure A.1 – Dual conversion – direct-coupled flywheel .37
Figure A.2 – Line interactive – direct-coupled flywheel.37
Figure A.3 – Dual conversion – indirect coupled flywheel.37
Figure A.4 – Line interactive – indirect coupled flywheel .38
Figure A.5 – Double fed a.c. machine .38
Figure A.6 – Dual conversion with battery.38
Figure A.7 – Line interactive with battery .39
Figure B.1 – Single-phase non-linear load .40
Figure C.1 – Three-phase non-linear load.42
Figure D.1 – Input mains failure test method.43
Figure E.1 – Series connected type 1 .44
Figure E.2 – Series connected type 2 .45
Figure E.3 – Line interactive .45
Figure E.4 – Typical UPS.46
Figure E.5 – Typical switchless dual feed UPS .47

Table 1 – Compatibility levels for individual harmonic voltages in mains power .21
Table 2 – Operating steady-state limit values for performance classes .21
Table 3 – Operating dynamic limit values for performance classes (note 1).22
Table 4 – Technical data sheets – Manufacturers declaration .26
Table 5 – Test methods for rotary UPS performance characteristics .32

88528-11  IEC:2004(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RECIPROCATING INTERNAL COMBUSTION ENGINE DRIVEN
ALTERNATING CURRENT GENERATING SETS –

Part 11: Rotary uninterruptible power systems –
Performance requirements and test methods

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 88528-11 has been prepared jointly by IEC technical committee 2:
Rotating machinery, and ISO technical committee 70: Internal combustion engines.
The text of this standard is based on the following documents:
FDIS Report on voting
2/1275/FDIS 2/1280/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – 88528-11  IEC:2004(E)
-
The committee has decided that the contents of this publication will remain unchanged until
2007. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
IEC 88528-11 is integrated into the ISO 8528 series listed below, under the general title
Reciprocating internal combustion engine driven alternating current generating sets:
Part 1: Application, ratings and performance
Part 2: Engines
Part 3: Alternating current generators for generating sets
Part 4: Controlgear and switchgear
Part 5: Generating sets
Part 6: Test methods
Part 7: Technical declarations for specification and design
Part 8: Requirements and tests for low-power generating sets (available in English only)
Part 9: Measurement and evaluation of mechanical vibrations (available in English only)
Part 10: Measurement of airborne noise by the enveloping surface method
Part 12: Emergency power supply to safety services

88528-11  IEC:2004(E) – 7 –
RECIPROCATING INTERNAL COMBUSTION ENGINE DRIVEN
ALTERNATING CURRENT GENERATING SETS –

Part 11: Rotary uninterruptible power systems –
Performance requirements and test methods

1 Scope
This International Standard, which forms part of the ISO 8528 series, specifies criteria,
including performance and test methods, for rotary uninterruptible power systems (UPS)
arising out of a combination of mechanical and electrical rotating machines. This standard
applies to power supplies primarily designed for supplying uninterrupted a.c. power to the
consumer. When operated without input mains feed, the power is provided by stored energy
and/or reciprocating internal combustion (RIC) engine and the output power is provided by
one or more rotating electrical machines.
This part 11 applies to a.c. power supplies primarily designed for supplying uninterruptible
electrical power for stationary land and marine use, excluding supplies for aircraft, land
vehicles or locomotives. It also excludes power supplies where the output power is generated
by static converters. (See IEC 62040-3.)
The use of a rotary UPS installation to improve the quality of a.c. power supply, to provide
voltage and/or frequency conversion, and to provide peak shaving is also described.
For some specific applications (for example, essential hospital supplies, offshore, non-
stationary applications, high rise buildings, nuclear, etc.) supplementary requirements may be
necessary. The provisions of this part of ISO 8528 should be used as a basis.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60034-1:2003, Rotating Electrical Machines – Part 1: Rating and performance
IEC 60034-22:1996, Rotating Electrical Machines – Part 22: AC generators for reciprocating
internal combustion (RIC) engine driven generating sets
IEC 60417 (all parts), Graphical symbols for use on equipment. Index, survey and compilation
of the single sheets
IEC 60529:1989, Degrees of protection provided by enclosures (IP Code)
IEC 61000, Electromagnetic compatibility (EMC)
ISO 3046-1:2003, Reciprocating internal combustion engines
ISO 7000, Graphical symbols for use on equipment
ISO 8178-1, Reciprocating internal combustion engines – Exhaust emission measurement –
Part 1: Test-bed measurement of gaseous and particulate exhaust emissions
ISO 8528-1, Reciprocating internal combustion engine driven alternating current generating
sets – Part 1: Application, ratings and performance

– 8 – 88528-11  IEC:2004(E)
-
ISO 8528-6, Reciprocating internal combustion engine driven alternating current generating
sets – Part 6: Test methods
ISO 8528-9, Reciprocating internal combustion engine driven alternating current generating
sets – Part 9: Measurement and evaluation of mechanical vibrations
ISO 8528-10, Reciprocating internal combustion engine driven alternating current generating
sets – Part 10: Measurement of airborne noise by the enveloping surface method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 General
3.1.1
generating set
one or more RIC engines to produce mechanical energy and one or more generators to
convert the mechanical energy into electrical energy together with components for
transmitting the mechanical energy (for example, couplings, gearbox) and where applicable
bearing and mounting components
3.1.2
uninterruptible power system (UPS)
power system for maintaining continuity of load power in the event of failure of the mains
power
3.1.3
rotary UPS
UPS where one or more electrical rotating machines provide the output voltage
3.1.4
converter
set of equipment, static or rotating, to convert one type of electric current to another type,
different in nature, voltage and/or frequency
3.1.5
power system reactor
regulated or non-regulated inductance in series with the input of some types of UPS
3.1.6
machine set
any combination of one or more electrical rotating machines
3.1.7
energy storage device
device to provide stored energy on failure of the normal power supply system. This energy
shall be available either during the total failure time or until the take over of a power supply by
the RIC engine
3.1.8
continuity of load power
availability of the power supplied to the load with voltage and frequency within steady-state
and transient tolerance bands and with distortion and power interruptions within the limits
specified for the load
88528-11  IEC:2004(E) – 9 –
3.2 Performance of systems and components
3.2.1
mains power
power normally continuously available which is supplied from the electrical power system or
by independent electrical power generation
3.2.2
backfeed
condition where a portion of the voltage or energy available within the UPS is fed back to any
of the input terminals, either directly or by a leakage path
3.2.3
linear load
load where the parameter Z (load impedance) is a constant when a variable sinusoidal voltage
is applied to it and that a sinusoidal voltage causes a sinusoidal current
3.2.4
non-linear load
load where the parameter Z (load impedance) is no longer a constant but is a variable
dependent on other parameters, such as voltage or time
3.2.5
power failure
any variation in the input voltage or frequency of the mains power not within acceptable limits
3.2.6
redundant operation
any operation with the addition of parallel functional units or groups of functional units in a
system to enhance the availability of load power
3.2.7
power conditioning mode
stable mode of operation that the UPS finally attains when operating under the following
conditions:
– normal power is present and within its given tolerance;
– full (100 %) stored energy available within its given restored energy time;
– the operation is or may be continuous;
– the load is within its given range;
– the output voltage is within its given tolerance.
Where a bypass is used:
– the input voltage is available and within specified tolerances;
– the phase lock is active, if present.
3.2.8
independent mode
operation of the UPS when operating under the following conditions:
– normal power is disconnected or is out of given tolerance;
– energy is from storage device or RIC engine;
– load is within the given range;
– output voltage and frequency are within given tolerances.

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-
3.2.9
bypass mode
state the UPS attains when operating and the load is supplied via the bypass
3.2.10
off mode
state that the rotary UPS attains when de-energized and at rest
3.2.11
synchronization
adjustment of an a.c. power source to match another a.c. source in frequency and phase
angle
3.2.12
load power
power which is supplied to the load from the UPS
3.2.13
asynchronous transfer
switching of load power between two sources that are not synchronized. This transfer must
happen with an interruption
3.3 Specified values
3.3.1
rated value
value of a quantity used for specification purposes, established for a specified set of operating
conditions of a component, device, equipment, or system
[IEV 151-16-08]
3.3.2
tolerance band
range of values of a quantity within specified limits
3.3.3
deviation
difference between the desired value and the actual value of a variable at a given instant
NOTE This definition applies whether the desired value is constant or varies in time.
[IEV 351-12-15]
3.3.4
rated voltage
input or output supply voltage for which equipment is designed or specified
3.3.5
rated frequency
input or output frequency as declared by the manufacturer
3.3.6
phase angle
angle (usually expressed in electrical degrees) between reference points on one or more a.c.
waveforms
3.3.7
crest factor
ratio of the peak value of a periodic waveform to its r.m.s. value

88528-11  IEC:2004(E) – 11 –
3.3.8
power
time rate of transferring or transforming energy or of doing work. (also called active power)
[IEV 111-13-30]
3.3.9
apparent power
product of the r.m.s. voltage U between the terminals of a two-terminal element or two-
terminal circuit and the r.m.s. electric current I in the element or circuit:
S=UI
[IEV 131-11-41]
3.3.10
ambient temperature
temperature of the air or other medium where the equipment is to be used
[IEV 826-01-04]
3.3.11
total harmonic distortion
ratio of the r.m.s. value of the harmonic content as a percentage of the r.m.s. value of the
fundamental component of the periodic function
3.3.12
recovery time
time interval between the moment a stabilized voltage or frequency leaves the steady-state
tolerance band until the instant when this quantity returns to and stays within the steady-state
tolerance band
3.3.13
stored energy time
minimum time during which the UPS will ensure conditions when the normal power fails
starting with the energy storage means being charged
3.4 Input values
NOTE These definitions are only valid in the power conditioning mode (normal mode).
3.4.1
input voltage tolerance
maximum continuous input voltage variation in normal operation
3.4.2
input power factor
ratio of the input active power to the input apparent power with the UPS operating at rated
input voltages at rated output power, and fully charged storage
3.4.3
high impedance mains failure
mains failure where the mains impedance as presented to the UPS input terminals is infinite
3.4.4
low impedance mains failure
mains failure where the mains impedance as presented to the UPS input terminals is
negligible
– 12 – 88528-11  IEC:2004(E)
-
3.5 Output values
3.5.1
output voltage
r.m.s. value (unless otherwise specified for a particular load) of the voltage between the
output terminals
3.5.2
output current
r.m.s. value of the current (unless otherwise specified for a particular load) from the output
terminals
3.5.3
rated load
load for which the system is defined
4 Symbols and abbreviations
Fundamental portion of power factor
cos φ
f
Rotary UPS output frequency in Hz
P Active power
S
Apparent power
U Rated output voltage of a rotary UPS
r
U Rectified voltage
c
U Rotary UPS output voltage ( r.m.s. line-line)
ac
Z Load impedance
5 Selection criteria
Complete application criteria should include the following features and shall be made
available by the system supplier:
– rotary UPS load requirements;
– operating time required;
– starting capability of large electric motors in the load;
– fault clearing capability;
– input power quality;
– ambient temperature;
– reliability;
– maintainability;
– required floor space;
– parallel operation requirement;
– operating efficiency;
– reduction and/or isolation of voltage harmonics and other deviations from input to output;
– reduction and/or isolation of current harmonics and other deviations from output to input;
– environmental requirements (noise, vibration, dust, electromagnetic compatibility, etc.);
– degree of separation from the mains in power conditioning mode (harmonics, full galvanic
isolation, etc.).
88528-11  IEC:2004(E) – 13 –
An input switching device shall be provided to isolate the rotary UPS from the incoming
mains.
Means shall be provided to prevent reverse power flow, if required.
6 General description
Types of uninterruptible power systems are shown in Figure 1.
Uninterruptible power system (UPS)

Rotary UPS systems Static UPS systems
IEC 62040-3
IEC  033/04
Figure 1 – Types of UPS systems
6.1 Rotary UPS
Rotary uninterruptible power supply as defined in this standard is achieved by a combination
of electrical and when required RIC engines and generating sets.
In order to achieve an uninterrupted supply of power during a short interruption period, a
pneumatic, kinetic, electrochemical, or other such energy storage device is used. For
extended periods of operation an RIC engine or generating set may be utilized to provide the
energy supply. (See ISO 8528-1, subclause 6.5.)
6.2 Types of rotary UPS
Various configurations of rotary UPS systems are possible depending upon the application
and performance requirements. It is important that the configuration shall be taken into
account by the customer when agreeing upon the requirements with the manufacturer.
6.2.1 Series connected rotary UPS
Figure 2 illustrates a series connected rotary UPS.
M G
2 3
G
IEC  034/04
Key
1 primary path 3 inverter 5 RIC engine 7 AC output G generator
2 rectifier 4 energy storage 6 AC input M motor
Figure 2 – Typical example series connected rotary UPS

– 14 – 88528-11  IEC:2004(E)
-
In most series connected cases, two independent electrical machines (motor and generator)
or a combination of both is used as the final output of the rotary UPS. In most cases the final
output machine pair or combination machine is direct connected to the mains source with an
alternate path to the mains through power converters allowing connection to a stored energy
source. Direct connection provides higher efficiency and reduced input harmonics. Some
series connected cases rely on the alternate path.
– Rotary UPS power supply to the electrical consumer is taken from the rotary UPS system,
independent of whether the external power supply system is intact or has failed. In the
event of a mains failure or if the power is outside the permissible tolerance limits of the
input of the rotary UPS system, energy is provided from a short term stored energy source
until a RIC engine can be started, if the installation is so equipped. When the installation
is equipped with an engine, the required energy for continuity of the power supply to the
electrical consumer is taken for a practically unlimited time from the engine (sufficient fuel
supply assumed) (see also Clause 5). After restoration of the mains, supply power for the
rotary UPS system is again taken from the mains system.
– The engine may be equipped with its own generator and transfer switch configured to
supply power to the input of the series connected rotary UPS. The engine can also be
directly connected by a clutch to the MG set of the series connected rotary UPS.
– Back feed to the mains during a short circuit of the mains or during rotary UPS transition
modes must be prevented to maintain rotary UPS output power and prevent internal
damage of the rotary UPS. In the series connected case with a single power path (i.e.
rectifier to inverter to MG set) back feed prevention is provided by phase control of the
rectifier. In series connected rotary UPS cases with a dual power path (i.e. static switch to
MG set and rectifier to inverter to MG set) back feed is prevented by phase control of the
sub-cycle static switch and the rectifier.
– In the series connected rotary UPS isolation protection of the consumer’s load is provided
by the electrical to mechanical and back to electrical power conversions of the final output
MG set. The level of isolation protection depends on the MG set, insulation, air gaps, etc.
The generator provides reactive power compensation and supplies the harmonics and
unbalance as required by the load.
– In the event of mains failure or when exceeding the permissible tolerance limits of the
electrical consumer, the power supply, practically without any interruption, will change
over to short term stored energy and then to an engine when so equipped.
– Upon restoration of the stabilized mains, supply is effected synchronously and without
interruption.
6.2.2 Line interactive rotary UPS
Figure 3 illustrates a line interactive rotary UPS.
1 2
IEC  035/04
Key
1 AC input 3 power system reactor
2 AC output 4 machine set
Figure 3 – Typical example of a line interactive rotary UPS
A machine set including a generator, energy storage means and an RIC engine if so
equipped, is operated in parallel with the mains system.
The energy storage and RIC engine may all be coupled on the same shaft, or realized as
separate units with an indirect coupling (electrical, hydraulic, mechanical, etc.).

88528-11  IEC:2004(E) – 15 –
– Power is taken from the mains system, provided the voltage and frequency lie within the
tolerance range specified for the mains system or electrical consumers.
– The rotary UPS system is also supplied with energy from the mains system. A certain
degree of isolation between the mains system and the electrical consumer is achieved by
means of an impedance (reactor). This is installed in the incoming feeder so that voltage
deviations can be compensated to suit system requirements by the synchronous machine
(s) that are connected in parallel.
– The power system reactor limits back feed in case of low impedance mains failure and
allows independent control of output voltage. The generator provides reactive power
compensation and supplies the harmonics and unbalance as required by the load.
– In the event of mains system failure or when exceeding the permissible tolerance limits of
the electrical consumer, the power supply will change over to the synchronous converter
machine or to the synchronous generator of the twin machine set.
The energy required for driving the rotary UPS is taken for either a limited time from the
energy storage device or a practically unlimited time from an RIC engine (sufficient fuel
supply assumed) (see also Clause 5).
Continuation of energy supply from the restored and stabilized mains is effected
synchronously and without interruption.
6.3 Parallel operation of a rotary UPS installation
6.3.1 General
Rotary UPS systems may be operated in parallel to increase power output, to increase
availability, or to provide redundancy.
6.3.2 Parallel operation
Parallel operation of a rotary UPS system is illustrated in Figure 4. An arrangement of rotary
UPS systems of identical rating is usual.
1 2
IEC  036/04
Key
1 AC input 2 AC output 3 UPS
Figure 4 – Parallel operation of a rotary UPS
6.3.3 Redundant operation
Increasing the number of active rotary UPS units by at least one active unit to ensure full
supply of electrical consumers in cases of maintenance or failure of a single rotary UPS unit
(1 + n active redundancy).
– 16 – 88528-11  IEC:2004(E)
-
6.4 Power system changeover with rotary UPS installations (bypass)
Bypass can be provided, to electrically isolate the rotary UPS, in case the nominal input and
output frequencies are the same and where the average mains power availability is
acceptable for the load. Bypass can be manual, automatic, or a combination of both.
Bypass circuits may be individual or common in the case of parallel rotary UPS systems. See
Figure 5.
1    4 2
IEC  037/04
Key
1 AC input 2 AC output 3 rotary UPS 4 bypass
Figure 5 – Bypass operation
Automatic transfer of electrical consumers supply to the mains system may be provided if a
fault occurs in the rotary UPS system (passive redundancy).
Transfer is effected either with or without interruption depending on the rotary UPS system
design. Mainly, however, transfer is effected without interruption.
A transfer can be without interruption if a rotary UPS system and utility were synchronized, or
with a short interruption if they are not synchronized. This transfer may be (temporarily)
inhibited when the utility is not available or out of tolerance.
6.5 Enclosure protection
The equipment shall be provided with a surrounding case or enclosure constructed to provide
a minimum degree of protection IP2X, (IEC 60529) to personnel against accidental contact
with energized, hot or moving parts.
7 Modes of operation
Typical operation of a rotary UPS is shown in Figure 6.

88528-11  IEC:2004(E) – 17 –
Y
9 10
1 2 3
X
IEC  038/04
Key
1 time of power failure 6 dynamic limit values (Table 3) 11 stored energy time
2 time of power return 7 steady-state limit values (Table 2)
3 time of synchronization 8 synchronization X axis time t in seconds
4 RIC engine if used 9 power conditioning mode Y axis output voltage frequency
5 recovery time 10 independent mode

Figure 6 – Illustration of rotary UPS operation
7.1 Power conditioning mode
A stable mode of operation that a rotary UPS finally attains when operating under the
following conditions:
– normal power is present and within specified tolerances;
– energy storage means are being charged or fully charged;
– the operation is or may be continuous;
– the load is within its given range;
– the output voltage is within its given tolerance;
– RIC engine if provided ready to start.
7.2 Independent mode
The operation of the rotary UPS when operating under the following conditions:
– normal power is disconnected or is out of given tolerances;
– the energy is from storage device or RIC engine, if provided;
– load is within the given range;
– output voltage is within given tolerances.

– 18 – 88528-11  IEC:2004(E)
-
7.3 Bypass mode
The state that the rotary UPS attains when operating the load supplied via the bypass supply.
7.4 Off mode
The state that the rotary UPS attains when de-energized and at rest.
7.5 Transitions
The 4 main operating modes and the 12 possible transitions are shown in Figure 7.
A
B
7 1
C D
IEC  039/04
Key
A independent mode C bypass mode
B power conditioning mode D off mode
Figure 7 – Operating modes
7.5.1 Transition 1, starting the system with mains voltage present
Start-up may require the RIC engine or a pony motor to bring the rotating parts to speed
before energy can be taken from the grid. With mains voltage and frequency within tolerance,
the system enters the power conditioning mode.
The units of a multi-module system can be started sequentially, even when the total load is
more that the first unit can supply when the excess load is supplied via the bypass from the
mains.
NOTE Start-up (transitions 1, 2, or 12) is at least inhibited when an emergency OFF button is active.
7.5.2 Transition 2, start-up without mains voltage (black start)
This start-up method is only useful for systems with a permanent energy source, i.e. an RIC
engine. Otherwise, the independent mode could only be maintained for a limited time. Black
start is the ability to start using only internal energy sources like charged batteries and fuel.
Internal energy sources that cannot be maintained during at least one day in “Off” mode are
assumed as discharged at the beginning of the black start. The units of a multi-module system
can be started
...