Nidec LEROY-SOMER R251 Instruction Manual

R251
VOLT
FREQ. & L.A.M. CONFIG.
STAB
110
E+ E-
0V
0
9
8
7
6
5
4
3
2
1
o
1
2
3
5
6
7
9
8
4
60Hz
65Hz
57Hz
47.5Hz
50Hz
KNEE
SPECIAL
LAM
OFF
OFF
13%
13%
25%
25%
LAM
KNEE
KNEE
LAM OFF
LAM OFF
LAM OFF
R251
AVR
Installation and maintenance

2024.01 / g
Electric Power Generation
2
Installation and maintenance
R251
AVR
4092 en -
SAFETY MEASURES
Before using your machine for the rst time,
it is important to read the whole of this
installation and maintenance manual.
All necessary operations and interventions
on this machine must be performed by a
qualied technician.
Our technical support service will be pleased
to provide any additional information you
may require.
The various operations described in this
manual are accompanied by
recommendations or symbols to alert the
user to potential risks of accidents. It is vital
that you understand and take notice of the
following warning symbols.
WARNING
Warning symbol for an operation capable
of damaging or destroying the machine
or surrounding equipment.
Warning symbol for general danger to
personnel.
Warning symbol for electrical danger to
personnel.
All servicing or repair operations
performed on the AVR should be
undertaken by personnel trained in the
commissioning, servicing and
maintenance of electrical and
mechanical components.
When the generator is driven at a
frequency below 28 Hz for more than 30
seconds with an analogue AVR, its AC
power supply must be disconnected.
WARNING
This AVR can be incorporated in a EC-
marked machine.
This manual is to be given to the end
user.
© 2024 Moteurs Leroy-Somer SAS
Share Capital: 32,239,235 €, RCS Angoulême
338 567 258.
We reserve the right to modify the characteristics
of this product at any time in order to incorporate
the latest technological developments. The
information contained in this document may
therefore be changed without notice.
This document may not be reproduced in any
form without prior authorization.
All brands and models have been registered and
patents applied for.
This manual concerns the alternator AVR which you have just purchased.
We wish to draw your attention to the contents of this maintenance manual.

2024.01 / g
Electric Power Generation
3
Installation and maintenance
R251
AVR
4092 en -
CONTENTS
1 - POWER SUPPLY ...............................................................................................................4
1.1 - SHUNT excitation system ............................................................................................4
2 - R251 AVR ...........................................................................................................................5
2.1 - Characteristics .............................................................................................................5
2.2 - U/F function and LAM...................................................................................................5
2.3 - AVR options..................................................................................................................6
2.4 - LAM Characteristics ....................................................................................................6
2.5 - Typical e󰀨ects of the LAM.............................................................................................7
3 - INSTALLATION - COMMISIONING ...................................................................................8
3.1 - Electrical checks on the AVR ........................................................................................8
3.2 - Settings........................................................................................................................8
3.3 - Electrical faults.............................................................................................................9
4 - SPARE PARTS .................................................................................................................10
4.1 - Designation................................................................................................................10
4.2 - Technical support service. ..........................................................................................10
Disposal and recycling instructions
The R251 is an IP00 product. It must be installed inside a unit so that this unit’s cover can
provide IP20 minimum total protection (it must only be installed on our alternators in the
appropriate location so that when viewed externally, it has a higher degree of protection than
IP20).

2024.01 / g
Electric Power Generation
4
Installation and maintenance
R251
AVR
4092 en -
1 - POWER SUPPLY
1.1 - SHUNT excitation system
The SHUNT excitation alternator is auto-
excited with a R251 voltage regulator.
The regulator controls the excitation current
according to the alternator’s output voltage.
With a very simple conception, the SHUNT
excitation alternator does not have a short
circuit capacity.
The R251 is a R250 with a specic excita-
tion ceiling = 4 A during 30 s (set for the
dedicated single phase alternator with type
M or M1).
4 x holes Ø 5.8 x
50 x 115 mm
140 mm
75 mm
SHUNT SYSTEM
T3
T4
Varistor
5+ 6-
T1
T2
STATOR : 4 wires (marking T1 to T4)
MAIN FIELD
Field
Induced
R251
VOLT
FREQ. & L.A.M. CONFIG.
STAB
F1
Slow fuse
250V 8 A
P1 Voltage
P2 Stability
110
E+ E-
0V
0
9
8
7
6
5
4
3
2
1
o
1
2
3
5
6
7
9
8
4
60Hz
65Hz
57Hz
47.5Hz
50Hz
KNEE
SPECIAL
LAM
OFF
OFF
13%
13%
25%
25%
LAM
KNEE
KNEE
LAM OFF
LAM OFF
LAM OFF
External potentiometrer
for voltage adjusting
ST4 Option
Frequency selector 50 Hz
/ 60 Hz for U/F fonction
and LAM adjustement

2024.01 / g
Electric Power Generation
5
Installation and maintenance
R251
AVR
4092 en -
2 - R251 AVR
2.1 - Characteristics
- Storage: -55°C; +85°C
- Operation: -40°C; +70°C
- Voltage regulation: around ± 0,5 %
- Supply range/voltage detection 85 to 139V
(50/60Hz).
- Rapid response time (500 ms) for a
transient voltage variation amplitude of ±
20 %.
- Voltage setting P1
- Stability setting P2
- Power supply protected by 8 A fuse,
replacement product: Ferraz-Shawmut
T084013T fast-blow fuse, 8 A FA 250 V,
breaking capacity 30 kA.
2.2 - U/F function and LAM
The threshold position (50 Hz - 60 Hz) to
action the U/F function as well as the LAM
setting type is selected using the
potentionmeter.
WARNING: The jumper settings must
correspond to the rated operating
frequency (see the nameplate on the
alternator).
Risk of destruction for the alternator.
The threshhold position and LAM function
settings are done with the jumper.
Operating at 50 Hz: (U/F gradient)
0: threshold at 48 Hz without LAM for
impacts between 30 and 40% of the rated
load.
1: threshold at 48 Hz with LAM 13% for
impacts between 40 and 70% of the rated
load.
2: threshold at 48 Hz with LAM 25% for
impacts > 70% of the rated load.
Operating at 60 Hz: (U/F gradient)
3: threshold at 58 Hz without LAM for
impacts between 30 and 40% of the rated
load.
4: threshold at 58Hz with LAM 13% for
impacts 40 and 70% of the rated load.
5: threshold at 58Hz with LAM 25% for
impacts > 70% of the rated load.
Specic operating
6: threshold at 57Hz without LAM for speed
variations at a steady state > 2 Hz
7: threshold at 65Hz without LAM for
variable speed and tractelec / gearlec (U/F
gradient).
8: special: the factory setting 48Hz 2U/F
gradient ; a special programme is possible
on request. This programme must be
specied before ordering, during the project
study.
9: threshold at 47.5 Hz without LAM for
speed variations at a steady state > 2 Hz.
For hydraulic applications, it is advisable to
select:
- position 0 for 50 Hz
- position 3 for 60 Hz
0
9
8
7
6
5
4
3
2
1
oo
11
22
33
55
66
77
99
88
44
60Hz60Hz
65Hz65Hz
57Hz57Hz
47.5Hz47.5Hz
50Hz50Hz
KNEEKNEE
SPECIALSPECIAL
LAMLAM
OFFOFF
OFFOFF
13%13%
13%13%
25%25%
25%25%
LAMLAM
KNEEKNEE
KNEEKNEE
LAM OFFLAM OFF
LAM OFFLAM OFF
LAM OFFLAM OFF

2024.01 / g
Electric Power Generation
6
Installation and maintenance
R251
AVR
4092 en -
2.3 - AVR options
Potentiometer for remote voltage
adjustment, 1000 Ω / 0.5 W min: adjustment
range ± 5%.
- Remove the ST4 jumper.
For wiring up the external potentiometer;
the “earth” wires must be isolated as
well as the potentiometer terminals
(wires at the same voltage as the power).
2.4 - LAM characteristics (Load
Acceptance Module)
2.4.1 - Voltage drop
The LAM system is integrated in the AVR It
is active as standard. It can be adjusted to
13% or 25%.
- Role of the «LAM» (Load Adjustment
Module):
On application of a load, the rotation speed
of the generator set decreases. When it
passes below the preset frequency
threshold, the LAM causes the voltage to
drop by approximately 13% or 25% and
consequently the amount of active load
applied is reduced by approximately 25% to
50%, until the speed reaches its rated value
again.
Hence the “LAM” can be used either to
reduce the speed variation (frequency) and
its duration for a given applied load, or to
increase the applied load possible for one
speed variation (turbo-charged engines).
To avoid voltage oscillations, the trip
threshold for the “LAM” function should be
set approximately 2 Hz below the lowest
frequency in steady state.
It is advised to use the “LAM” at 25% for load
impacts > at 70% of the genset rated power.
2.4.2 - Gradual voltage return function
During load impacts, the function helps the
genset to return to its rated speed faster
thanks to a gradual increase in voltage
according to the following principles:
- if the speed drops between 46Hz and
50Hz, the rated voltage follows a fast
gradient as it is restored.
- if the speed drops below 46 Hz, since the
engine needs more help, the voltage follows
a slow gradient as it returns to the reference
value.
LAM
U
N
0
48 or 58 Hz
0,85 U N
Voltage
U/f
50 or 60 Hz
fC fN
Voltage
ST3
0
Time
Drop N < 46 Hz
U
Drop N > 46 Hz

2024.01 / g
Electric Power Generation
7
Installation and maintenance
R251
AVR
4092 en -
2.5 - Typical e󰀨ects of the LAM with a
diesel engine or without a LAM (U/F
only)
2.5.1 - Voltage
2.5.2 - Frequency
2.5.3 - Power
UN
0
0,9
0,8
(U/f)
with
LAM Time
without LAM
1 s 2 s 3 s
Transient voltage drop
0,9
0,8
fN
Max speed drop
0
with
LAM
Time
without
LAM
1 s 2 s 3 s
01 s 2 s 3 s
Time
LAM
Load variation
Load on shaft (kW)
Shedding due to "LAM"

2024.01 / g
Electric Power Generation
8
Installation and maintenance
R251
AVR
4092 en -
3 - INSTALLATION -
COMMISSIONING
3.1 - Electrical checks on the AVR
- Check that all connections have been
made properly as shown in the attached
wiring diagram.
- Check that the position of the jumper
corresponds to the operating frequency.
- Check whether the ST4 jumper or the
remote adjustment potentiometer have
been connected.
3.2 - Settings
The di󰀨erent settings made during the
trial are to be done by qualied personnel.
Respecting the load speed specied on
the nameplate is vital in order to start a
settings procedure. After operational
testing, replace all access panels or
covers.
The only possible settings on the
machine are to be done with the AVR.
3.2.1 - R251 settings (SHUNT system)
Initial potentiometer positions
- voltage setting potentiometer P1 for the
AVR: full left
- remote voltage setting potentiometer: in
the middle.
Operate the alternator at its rated speed: if
the voltage does not rise it is necessary to
re-magnatise the magnetic circuit.
- slowly adjust the voltage potentiometer of
the AVR P1 until the output voltage reaches
its rated value.
- Stability setting with P2.
3.2.2 - Special type of use
Excitation circuit E+, E- must not be left
open when the machine is running: AVR
damage will occur.
3.2.2.1 - R251 eld weakening (SHUNT)
The exciter is switched o󰀨 by disconnecting
the AVR power supply (1 wire - 0 or 110V).
Contact rating: 16A - 250V AC.
Do not reclose the power supply until the
voltage has reached a value ≤15% of the
rated voltage (approximately 5 seconds
after opening).
3.2.2.2 - R251 eld forcing
Battery must be isolated from the earth.
Exciter eld may be at line potential.
WARNING
WARNING
E+
E-
0V 110
Battery (B Volt)
+
-
t
(400V - 10A)
Excitation Inducer
Diode
E+
E-
0V 110

2024.01 / g
Electric Power Generation
9
Installation and maintenance
R251
AVR
4092 en -
3.3 - Electrical faults
Fault Action E󰀨ect Check/Cause
No voltage at
no load on
start-up
Connect a new battery
of 4 to 12 volts to
terminals E- and E+,
respecting the polarity,
for 2 to 3 seconds
The alternator builds up and its
voltage is still correct when the
battery is removed
- Lack of residual magnetism
The alternator builds up but its
voltage does not reach the rated
value when the battery is
removed
- Check the connection of the voltage
reference to the AVR
- Faulty diodes
- Armature short-circuit
The alternator builds up but its
voltage disappears when the
battery is removed
- Faulty AVR
- Field windings open circuit (check
winding)
- Revolving eld coil open circuit (check the
resistance)
Voltage too
low Check the drive speed
Correct speed
Check the AVR connections (AVR may be
faulty)
- Field windings short-circuited
- Rotating diodes burnt out
- Revolving eld coil short-circuited (check
the resistance)
Speed too low
Increase the drive speed (do not touch the
AVR voltage setting before running at the
correct speed)
Voltage too
high
Adjust AVR voltage
potentiometer Adjustment ine󰀨ective - Faulty AVR - 1 faulty diode
Voltage
oscillations
Adjust AVR stability
potentiometer
- Check the speed : possibility of cyclic
irregularity
- Loose connections
- Faulty AVR
- Speed too low when on load (or U/F bend
set too high)
Voltage
correct at no
load and too
low when on
load (*)
Run at no load and
check the voltage
between E+ and E- on
the AVR
- Check the speed (or U/F bend set too
high)
- Faulty rotating diodes
- Short-circuit in the revolving eld coil
(check the resistance)
- Faulty exciter armature (check the
resistance)
(*) Caution : For single-phase operation, check that the sensing wires coming from the AVR are correctly connected to
the operating terminals.
Voltage
disappears
during
operation
Check the AVR, the
surge suppressor, the
rotating diodes and
replace any defective
components
The voltage does not return to the
rated value
- Exciter winding open circuit
- Faulty exciter armature
- Faulty AVR
- Revolving eld coil open circuit or
short-circuited
Warning: after operational testing, replace all access panels or covers.

2024.01 / g
Electric Power Generation
10
Installation and maintenance
R251
AVR
4092 en -
4 - SPARE PARTS
4.1 - Designation
Description Type Code
AVR R251 AEM 110 RE 021
4.2 - Technical support service
Our technical support service will be
pleased to provide any additional
information you may require.
For all spare parts orders or technical
support requests, send your request to
[e-mail] or your
nearest contact, whom you will nd at
www.lrsm.co/support indicating the type
and the code number of the AVR.
To ensure that our products operate correctly
and safely, we recommend the use of
original manufacturer spare parts.
In the event of failure to comply with this
advice, the manufacturer cannot be held
responsible for any damage.