Seg MRM3 User manual

MRM3 –Motor Protection Relay

2TB MRM3 07.01 E
Contents
1 Introduction and Application
2 Characteristics and Features
3 Design
3.1 Connections
3.1.1 Analog Inputs
3.1.2 Output Relays
3.1.3 Digital Inputs
3.1.4 Low/High Range of the Digital Inputs
3.2 Front plate
3.2.1 Indicating LEDs
3.2.2 Adjusting LEDs
3.3 Analog part
3.4 Digital part
4 Working Principle
4.1 Start Recognition
4.1.1 Criteria for Blocking the Start
4.2 Thermal Image
4.3 Requirement on the Main Current
Transformers
5 Operation and Adjustments
5.1 Displayed text for parameter settings
5.2 Settting Procedure
5.3 System parameters
5.3.1 Presentation of Measuring Values as
Primary Quantities on the Display
(Iprim Phase)
5.3.2 Rated -Frequency
5.3.3 Operating Hour Meter (h)
5.3.4 Number of Motor Starts (No.)
5.3.5 Indictation of the Activation Store
5.3.6 Parameter Set Changeover Switch (P2)
5.4 Protection Parameters
5.4.1 Thermal Overload Protection (k x IB)
5.4.2 Heating Period Constant τWand
Cooling-Down Time Factor τC
5.4.3 t2x and t6x Minimal Trip Time During
the Starting Process.
5.4.4 Phase Undercurrent Element (I<)
5.4.5 Phase Overcurrent Element (I>)
5.4.6 Trip Characteristics for the Phase Over-
current Element (I>+CHAR)
5.4.7 Tripping Time or Time Factor for the
Phase Overcurrent Element (I>+t>)
5.4.8 Reset Mode for the Trip Characteristics
in the Phase Current Path (I>+CHAR+t>)
5.4.9 Phase Short-Circuit Trip (I>>) and
(I>>+Start)
5.4.10 Negative Phase Sequence
5.4.11 Earth Fault Element (IE>)
5.4.12 Trip Characteristics for the Earth Fault
Element (IE>+CHAR)
5.4.13 Tripping Time or Time Factor for the
Earth Fault Element (IE>+t>)
5.4.14 Reset Time for the Earth Fault Element
(IE>+CHAR+t>)
5.4.15 Tripping Time for the CB Failure-Protec-
tion (CB+t>)
5.4.16 External Trip (delayed) (Trip+t>)
5.4.17 Trip Blocking in case of Excessive Phase
Current (Trip+Block)
5.5 Start Supervision
5.5.1 Duration of a Start Cycle (No.+Start)
5.5.2 Number of Starts per Cycle (No.+Start)
5.5.3 Start Blocking Time (Start+Block+t>)
5.5.4 Maximal Start Time (Start+t>)
5.6 Interface Parameters
5.6.1 Adjustment of the Slave-Address (RS)
5.6.2 Adjustment of the Baud-Rate (only for
Modbus Protocol)
5.6.3 Adjustment of the Parity (only for
Modbus-Protocol)
5.7 Fault Recorder (FR)
5.7.1 Fault Recorder
5.7.2 Number of Fault Recordings
5.7.3 Adjustment of the Trigger Event
5.7.4 Pre-Trigger Time (Tvor)
5.8 Setting of the Clock
5.9 Additional Functions
5.9.1 Blocking of the Protective Functions
5.9.2 Allocation of the Reset Functions
5.9.3 Allocation of the Output Relays
5.10 Measuring Value and Fault Indications
5.10.1 Measuring Value Indications
5.10.2 Units of the Displayed Measuring Values-
5.10.3 Indication of the Fault Data
5.10.4 Fault Memory
5.11 Reset
5.11.1 Erasure of the Fault Memory
5.11.2 Reset of the Thermal Memory
5.12 Digital Inputs
5.12.1 Parameter Set Changeover Switch
5.12.2 External Trigger of the Fault Recorder
5.12.3 Recognition of “Motor Running”
Condition
5.12.4 Undelayed External Trip
5.12.5 Delayed External Trip

TB MRM3 07.01 E 3
6 Notes on Relay Tests and Commissioning
6.1 Connection of the auxiliary voltage
6.2 Testing of Output Relays and LEDs
6.3 Test circuit for MRM3
6.3.1 Checking of Input Circuits and of the
Measuring Values
6.3.2 Testing the START-STOP-RUNNING
Recognition
6.3.3 Testing the Pick-Up and Disengaging
Values
6.3.4 Testing the thermal image
6.3.5 Testing the Control Inputs
6.3.6 Testing the CB Failure Protection
6.4 Primary Test
6.5 Maintenance
7 Technical Data
7.1 Measuring input
7.2 Common data
7.3 Setting ranges and steps
7.3.1 System parameter
7.3.2 Time overcurrent protection
7.3.3 Load Unbalance Protection
7.3.4 Earth fault protection
7.3.5 Circuit breaker failure protection
7.3.6 External trip delay
7.3.7 Trip blocking beginning with the
adjusted rated current
7.3.8 Start parameter
7.3.9 Interface parameter
7.3.10 Fault recorder parameter
7.4 Tripping characteristics
7.4.1 Thermal image
7.4.2 Initial load factor
7.4.3 Tripping of t2x and t6x - times
7.4.4 Inverse time overcurrent protection
7.5 Trip characterisitcs
7.6 Output relays
8 Order form

4TB MRM3 07.01 E
1 Introduction and Application
The motor protection relay MRM3 offers reliable pro-
tection for LV and MV motors which are either oper-
ated via power contactors or power circuit breakers.
The following functions are integrated into this relay:
•Overload protection acc. to IEC 255-8 in consid-
eration of the initial load factor (thermal image)
•Definite undercurrent protection
•Definite time overcurrent protection (DMT)
•Inverse time overcurrent protection (IMT) with select-
able trip characteristics
•Short-circuit protection
•Load unbalance supervision with definite or inverse
trip characteristics
•Earth-fault detection with suppression of harmonics
The MRM3 recognises the “Start-Up“ and “Motor Run-
ning“ phase.
Motors with a limited number of starts can be con-
trolled by the start limiting function of the relay.
The earth-fault supervision is either realised in Holm-
green connection or by means of a core-type current
transformer.
The motor can be stopped in delayed or undelayed
mode via digital inputs.
The MRM3 is available with rated currents of 1A or
5A.
Important:
For additional common data of all MR-relays please
refer to manual "MR - Digital Multifunctional relays".
On page 45 of this manual you can find the valid
software versions.
2 Characteristics and Features
•Microprocessor technology with self-supvervision,
•Measuring of phase currents as RMS value,
•Digital filtering of the earth current with discrete Fou-
rier analysis, by which the influence of interference
signals, such as harmonics and transient DC com-
ponents during an earth-fault are suppressed.
•Two sets of parameters,
•Operating hour meter,
•Complies with the requirements of IEC 255-8,
VDE435, part 301-1 for overload relays,
•Definite time undercurrent protection,
•Selectable protective functions : Definite time over-
current protection (DMT) and inverse time overcurrent
protection (IMT)
•Selectable IMT trip characteristics of IEC 255-4:
Normal inverse (Type A)
Very inverse (Type B)
Extremely inverse (Type C)
Special-purpose characteristics
•Reset mode for DMT/IMT trip characteristics is se-
lectable,
•Definite element for short-circuit high-speed trip
•Single-step earth fault supervision,
•Load unbalance protection with inverse or definite
trip characteristics (NPS),
•CB failure protection,
•Display of the measuring values as primary quanti-
ties,
•Measuring of the phase currents during short-circuit
free operation,
•Blocking of the individual protective elements or the
trip elements can be set freely,
•The protective functions can be freely allocated to
the output relays. (RelayMatrix),
•Suppression of an LED indication after activation
(LED flash),
•„Manual/Automatic“ reset function of the trip ele-
ments adjustable via the configuration matrix,
•Saving of trip values and the switch-off times (tCBFP) of
25 fault events (voltage fail-safe)
•Recording of up to 8 fault events with time stamp,
•Display of date and time,
•Trip via digital inputs,
•Rack mounting, with self-acting short-circuit mecha-
nism for CT circuits,
•Possibility of serial data exchange via the RS485 in-
terface, optionally with SEG RS485 Pro-Open-Data
Protocol or Modbus Protocol.

TB MRM3 07.01 E 5
3 Design
3.1 Connections
Figure 3.1: Connection Diagram MRM3
P1
P2
S1
S2
P1
P2
S1
S2
P1
P2
S1
S2
I1
I2
I3
IE
L1.1
B3
B4 L1.2
L2.1
B5
L2.2
B6
L3.1
B7
L3.2B8
B1
B2
L
1
L2
L3
Figure 3.2: Measuring of phase currents and earth current detection
in Holmgreen connection (IE)
This kind of connection can be used where three
phase CTs are available and a combination of phase
and earth current measuring is required.
Figure 3.3: Measuring of earth current with core-type CT (IE)
With the combination of phase and earth current
measuring, CTs to be connected according to Figure
3.2. and Figure 3.3.

6TB MRM3 07.01 E
3.1.1 Analog Inputs
The analog input signals of the phase currents IL1 (B3 -
B4), IL2 (B5 - B6), IL3 (B7 - B8) and the earth current IE
(B1 - B2) are fed to the protection device via separate
input CTs.
The current measuring quantities are galvanical de-
coupled, analogously filtered, and then fed to the ana-
log/digital converter.
3.1.2 Output Relays
The MRM3 has 5 output relays. Two of these relays
with two change-over contacts and three relays with
one change-over contact each are used for signalling.
The protective functions can be freely allocated except
of those for the self-supervision relay.
•Relay 1: C1, D1, E1 and C2, D2, E2
•Relay 2: C3, D3, E3 and C4, D4, E4
•Relay 3: C5, D5, E5
•Relay 4: C6, D6, E6
•Relay 5: Self-supervision C7, D7, E7
All relays are operating according to the n. o. princi-
ple with the exception of the self-supervision relay,
which operates acc. to the n. c. principle.
3.1.3 Digital Inputs
The MRM3 has 7 digital inputs with fixed functions.
All inputs have a common reference point : Terminal
D8. (See Chapter 3.1)
No Terminal Function Coding
Plug
1C8 Externalreset 2
2 E8 External blocking 1
3 A2 Parameter set change-
over switch
3
4 A5 External trigger for the
fault recorder
4
5 A6 Identification „Motor
Running“
7
6 A7 Ext. trigger, undelayed 6
7 A8 Ext. trigger, delayed 5
3.1.4 Low/High Range of the Digital
Inputs
The MRM3 is equipped with a wide-range power
supply unit and hence the supply voltage is freely se-
lectable. The switching threshold of the digital inputs,
however, has to be fixed in compliance with the sup-
ply voltage. Two different switching thresholds can be
adjusted:
Range Plug U not active U active
Low Plugged in <= 8V >= 10V
High Open <= 60V >= 70V
Figure 3.4: Coding Plug

TB MRM3 07.01 E 7
3.2 Front plate
Figure 3.5: Front plate MRM3-IE
Figure 3.6: Front plate MRM3-I
The LEDs ϑ, h, RS and FR on the MRM3 emit a yellow
light, all other LEDs are bi-coloured. The LEDs at the left
next to the alphanumerical display give a green light
during measuring and a red one when a fault signal
occurs.
The LEDs underneath the <SELECT/RESET> - push but-
ton emit a green light during adjustment and inquiry of
the setting quantities left to the LEDs. They show a red
light if the printed setting quantities right to the LEDs
are activated.
3.2.1 Indicating LEDs
L1, L2, L3 Indication of the phase currents
E Indication of the earth current
I2 Indication of the unbalanced load
current (NPS)
ϑIndication of the temperature equivalent
h Operating hour meter
!Date and time
3.2.2 Adjusting LEDs
IB> Rated motor current
K Constant quantity (k*IB = 100%
thermal load)
τWHeating period constant
τCCooling down factor
t> Tripping times, generally
ϑ> Switching threshold of the thermal
overload alarm
No. Number of motor starts
CHAR Characteristics setting
I< Undercurrent setting
I> Overcurrent setting
I2> Load unbalance setting (NPS)
I>> Short-circuit setting
IE> Earth current setting
CB CB failure protection
Block Start blocking/Protective blocking
0 Current>0/<0 START/STOP
recognition
Start Start blocking/Start time
Trip External trip
FR Parameter for the fault recorder
RS Setting of the relay address
P2 Parameter set 2 is active
S/R Motor starting/Motor running

8TB MRM3 07.01 E
3.3 Analog part
The alternating currents injected by the CTs are con-
verted into galvanical isolated voltages via input
transmitters and burden in the analog part.
The effect of inductive and capacitive coupled interfer-
ences are suppressed by RC analog filters. The meas-
uring voltages are fed to the analog inputs (A/D trans-
former) of the micro-processor and then converted into
digital signals by means of sample and hold circuits.
These digitized values are then used for further proc-
essing. The measuring values are acquired at fn = 50
Hz (fn = 60 Hz) with a sampling frequency of 800 Hz
(960 Hz), and thus the instantaneous values of the
measured quantities are acquired every 1.25 ms
(1.04 ms).
3.4 Digital part
The protection relay is equipped with a powerful mi-
cro-controller, being the core element of the protection
unit. With this micro-controller all tasks are completely
digitally processed, from discretization of the measur-
ing quantities to protective tripping.
With the protection program, stored in the program
storage (EPROM), the micro-processor processes the
voltages applied to the analog inputs and from this
calculates the fundamental harmonics of the current.
Digital filtering (DFFT-Discrete Fast-Fourier-Transforma-
tion) for suppression of harmonics as well as suppres-
sion of DC components during the short-circuit is used
in the process.
The micro-processor compares the existing current with
the threshold value (setting value) stored in the parame-
ter storage (EEPROM) and up-dates the thermal image.
If a current exceeds the threshold value for longer than
the trip delay or if the thermal image exceeds its rated
value, a fault signal occurs. Dependent on their set-
tings, the output relays pick up as well. When setting
the parameters, all setting values are read-in by the
micro-processor and saved in the parameter storage.
The program flow is continuously monitored by the in-
corporated "Hardware-Watchdog". Processor failure is
signalled by the “Selfsupervision” output relay.
Figure 3.7: Block Diagram of Protective Functions

TB MRM3 07.01 E 9
4 Working Principle
4.1 Start Recognition
The MRM3 monitors the flow of the current from which
the following operational conditions of the motor are
gathered.
•STOP
•START
•RUNNING
Figure 4.1: Different Start-Up Behaviour of Motors
STOP - Condition:
If no current can be measured (I < Stop threshold),
STOP conditions are recognised after expiration of the
stop time.
Start/Stop Threshold
This threshold is fixed at 2% of IN
Stop time:
The Stop time is adjustable in order to tolerate
a brief off-time of the current flow (e.g. change-
over Star/Delta) from the START or RUNNING
conditions. STOP is only indicated if the current
was under 2% INfor longer than the stop time.
Based on this time the running down period
can be considered in a certain way for the LED
indication.
START-Condition:
START is only recognised if the previous condition was
STOP and the motor current has exceeded the start
threshold. If the STOP or RUNNING conditions are
recognised, the START condition is terminated.
Overload Threshold:
This corresponds to the permissible thermal con-
tinuous current k x IB and is adjusted by the pa-
rameter of the thermal image.
Starter Recognition Time:
This adjustable time has only to be extended for
special start procedures in order to prevent that
the RUNNING conditions are indicated too
early in advance.

10 TB MRM3 07.01 E
•No exeeding of the start threshold during pony mo-
tor start-up or when soft starters are used.
•Multistage resistance start where the start threshold is
either exceeded several times or not at all.
The time is running from the instance the start threshold
is exceeded. RUNNING is only accepted by the su-
pervision after the time has elapsed or the overload
threshold is undershot. If the overload threshold is not a
clear criterion, the time has to be set at least for so
long that the longest regular start procedure is cov-
ered.
RUNNING can be recognised in different ways:
•If the START has been successfully completed. This
is the case when the motor current has dropped
below k x IB and the start recognition time has
elapsed. (direct start)
or
•if the motor is connected across several resistance
steps, it is possible that the start threshold is
passed through repeatedly. RUNNING conditions
are recognised when the start recognition time has
run out after the last step and a current has settled
between 2% IN and k x IB t.
(Resistance start).
•if after STOP a motor current has settled between
2% IN and k x IB and the start recognition time
has elapsed. The overload threshold has not nec-
essarily to be exceeded.
(soft start)
•If the «Motor Running» input was activated but the
overload threshold is not (or not any longer) ex-
ceeded. (See Chapter 5.12.3 )
With the recognition of STOP, the RUNNING condi-
tions have ceased to exist.
Figure 4.2: Flow Diagram of the Start Conditions
4.1.1 Criteria for Blocking the Start
Number of monitored starts :
The MRM3 is equipped with a flexible supervision
element which can limit the sequence of possible
starts.
A start should be prevented if it is obvious that it is
likely to be interrupted due to overload so that in total
the down-time can be curtailed. If a start is not rec-
ommendable at a certain time (with the motor
switched off), the MRM3 activates an allocated output
relay until the waiting time has elapsed. Irrespectively
of the adjustment of this element, the thermal image is
always activated and shuts the motor down as soon as
the thermal overload threshold is reached (due to a
start or overload).
The protective element can either be tied to the thermal
image or be manually defined by the number of starts
and cycle duration.

TB MRM3 07.01 E 11
Number of Starts/Cycle Duration
These two are defined as parameters.
Example:
The motor should be allowed to be started three times
an hour:
This means that in theory the motor can be started
every 20 minutes (= 60 min/3).
From this it can be concluded that the load generated
by the start procedure has decayed after these 20
minutes. If the motor would be successfully started
three time in quick succession, an immediate fourth
start would overload the motor. The start blocking re-
lay would be activated and the next start would only
be advisable after about 20 minutes. The protective
element ensures that the start sequence is kept within
safe intervals but that at least three starts are allowed
during the given time frame. If the intervals between
each start are long enough then even more than three
starts an hour might be possible because the motor
was able to cool down in the mean time. The delay
can be firmly defined (through start blocking time) or
be automatically ascertained (VARI ) until the 20 min-
utes given in the example are over. The state of the
thermal image has no influence on the delay.
Figure 4.3: Relation Start Period/Start Blocking Time
Figure 4.4: Relation Start Period/Start Blocking Time with
firm Start Blocking Time
Thermal Image
A start is always possible as long as there is enough
thermal reserve for a start. This start limitation is a dy-
namic one and is orientated on the data the thermal
image is parameterized with. For this the MRM3 de-
tects the average thermal load of the latest starts. With
the motor shut down, the start blocking relay is acti-
vated for the time when there is not enough thermal re-
serve in the storage through cooling down to enable a
new start.
Figure 4.5: Start Blocking through Thermal Image

12 TB MRM3 07.01 E
4.2 Thermal Image
The fed thermal energy Q and the temperature ϑof
the motor when in steady state condition is propor-
tional to the square of the phase current (e.g. ohmic
losses and iron losses):
Q ∼I² oder ϑ∼I²
In the thermal image this temperature is described by
the temperature equivalent ϑ(in %). For loading with
the maximal permissible operational current k x IB, the
motor reaches the maximal permissible temperature ϑB.
if it has been in steady state condition for a certain
time. For this load the thermal equivalent is defined to
100% = trip threshold:
Stationary final value:
%100*
)I(k
=(%) 2
B
2
I
⋅
ϑ
Note:
When testing the thermal image it has to be taken into
consideration that in case k x IB is slightly exceeded
(= long tripping time), a small current change within
the permissible measuring tolerances can cause a high
dispersion of the tripping time (clearly by more than
1%). This is related to the slope of the trip characteris-
tic. Furthermore it is important to start from the same ini-
tial level of the image when testing. Otherwise the
tripping times may be shorter than expected.
Automatic Reset
During the starting process the MRM3 observes the
rise of the thermal image. From the average of the last
two successful starts the unit detects the start load. After
overload conditions, the thermal image is only re-
leased when the motor has cooled down far enough
to deal with the demand of a new start.
4.3 Requirement on the Main Current
Transformers
The CTs chosen have a considerable influence on the
accuracy of the protective system. In order to select the
right type of transformer, the requirements and condi-
tions on site have to be considered carefully.
Type of Transformer
Current transformers have to be designed as protection
transformers (P).
Overcurrent Factor:
To ensure precise operation of the protection unit even
under full short-circuit current, the chosen transformers
must not saturate in this current range. This means that
the overload factor must be sufficiently large.
Class
For the nominal range or the lower load range it has
to be taken into account that not only the basic accu-
racy of the MRM3 has to be considered but also the
transformer accuracy. This applies especially for cases
where the Holmgreen circuit is used and for low earth
fault currents in isolated networks.
Power Rating
The transformer must be rated sufficiently to cover all
measuring instruments and protective devices con-
nected as well as the losses on the transformer measur-
ing line without becoming overloaded.

TB MRM3 07.01 E 13
5 Operation and Adjustments
5.1 Displayed text for parameter
settings
Function Displayed Text Related LED References
Normal operation SEG
Exceeding the measuring range max. ϑ
Sec.transf.currents indication SEK L1, L2, L3,
E
Chap. 5.3.1
Rated frequency f = 50 / f = 60 Chap. 5.3.2
LED flashing after activation FLSH/NOFL Chap. 5.3.5
Parameter set change-over switch SET1, SET2, P2 Chap. 5.3.6
Blocking of a function EXIT LED of the blocked
parameter
Characteristics phase current DEFT,NINV, VINV, EINV,
LINV, RINV,
CHAR + I> Chap. 5.4.6
Characteristics earth current DEFT, NINV, VINV, EINV,
LINV, RINV, RXIDG
CHAR + IE>> Chap. 5.4.12
Characteristics DEFT, INVS CHAR + I2> Chap. 5.4.10
Reset mode 0s / 60s CHAR + I> + t>
CHAR + I2> + t>
CHAR + IE> + t>
Chap. 5.4.8
Chap. 5.4.14
Start blocking by thermal supervision AUTO Start + No Chap. 5.5.1
Auto.definition of the remaining
blocking time
VARI Start + block + t> Chap. 5.5.3
CB failure protection CBFP CB + t> Chap. 5.4.15
Inquiry of the fault memory FLT1, FLT2..... Trip = type dependent Chap. 5.10.3
Erase fault memory wait Chap. 5.10.4
Relay tripped TRIP Trip = type dependent
Reset the system SEG
Password inquiry PSW? LED of the set parameter
Hidden password „XXXX“ Chap. 5.2
Parameter to be saved? SAV?
Save parameter ! SAV!
Manual trip TRI?
Blocking of the protec.function BLOC, NO_B, PR_B, TR_B LED of the set parameter
Relay assignment z. B. _ 2 _ _ LED of the set parameter
Trip signal for the fault recorder P_UP; A_PI; TRIP; TEST FR Chap. 5.7.3
Number of fault events S = 2, S = 4, S = 8 FR Chap. 5.7.2
Indication of date and time Y = 01, M = 01, D = 04,
h = 12, m = 2, s = 12
!Chap. 5.8
Slave address of the serial interface 1-32 RS Chap. 5.6.1
Baud-Rate 1) 1200-9600 RS Chap. 5.6.2
Parity-Check 1) even odd no RS Chap. 5.6.3
Table 5.1: Indication Possibilities via the Display
1) Modbus only

14 TB MRM3 07.01 E
5.2 Settting Procedure
<SELECT/RESET>
short advancing the indication
long reset
<ENTER>
Saving of an entry
Before parameters can be set a password is inquired
(see chapter 4.4 of descrip. ”MR – Digital Multifunc-
tion Relay”).
5.3 System parameters
5.3.1 Presentation of Measuring Values as
Primary Quantities on the Display
(Iprim Phase)
This parameter makes it possible to present the indica-
tions of phase current and earth-fault current sepa-
rately, i.e as primary or secondary measuring value.
Currents in the kiloampere range are indicated with
the symbol of unit of measurement k (kilo) as three-digit
point.
Example:
A 1500/5 A CT is used with a primary current of
1380 A. The parameter for the CT primary current is
given in kiloampere.
•The parameter is set to ”1.50“ (kA). Then ”1K38“
is displayed as I-measurement.
•If the setting is set to ”sec.“, ”0.92“ x IN. is dis-
played as I-measurement.
Note:
The settings for the pick-up value are adjusted to a mul-
tiple of the secondary rated CT current.
The settings for phase and earth current transformers
can be done separately.
5.3.2 Rated -Frequency
The FFT-Algorithm used for the data acquisition needs
the set point of the rated frequency, i.e. 50 Hz or
60 Hz, for correct digital filtering of the earth current.
5.3.3 Operating Hour Meter (h)
As soon as the conditions START or RUNNING have
been recognised, the operating hour meter starts. The
meter can also be preset. Years and hours are shown
in two windows. After every 8760 h the value is car-
ried over to the window ”Year”.
In the display the years are marked with the letter “Y”
(engl.: year)
5.3.4 Number of Motor Starts (No.)
Every start is counted, even unsuccessful ones. The
number of motor starts can be preset.
5.3.5 Indication of pickup
If the momentary current drops below the pickup
threshold, e.g I>, after the relay was activated and
there was no tripping, then the activation is signalled
by short flashing of LED I>. The LED keeps flashing until
the <RESET> push-button is pressed. By setting the pa-
rameter to FLSH/NOFL, flashing can be suppressed.
5.3.6 Parameter Set Changeover Switch (P2)
By means of this switch two different parameter sets
can be activated. The changeover procedure can be
realised either by the software or via the digital input
(A2). If the parameter set changeover switch is ad-
justed to ”SET2“, the active parameter set can be
changed to ”SET1“ via the external input. If the
changeover switch is set to ”SET1“, then it can be
changed to ”SET2“ via the digital input.
The digital input does not change this parameter. The
LED P2 on the front cover always indicates which of
the parameter sets is active.
During the setting procedure the LED P2 gives off a yel-
low light.

TB MRM3 07.01 E 15
5.4 Protection Parameters
5.4.1 Thermal Overload Protection (k x IB)
With the product of setting values k x IBthe continu-
ously permissible maximal current of the motor is ad-
justed. At this current the thermal image reaches
100 % after a long period – i.e the trip threshold.
With IBnormally the rated current of the motor is ad-
justed and with k an overload factor (e.g. 1.05)
It is also possible to adjust the maximal continuous cur-
rent directly, if k = 1 was selected.
5.4.2 Heating Period Constant τ
ττ
τWand
Cooling-Down Time Factor τ
ττ
τC
With this time constant the thermal image is adapted
to the heating behaviour of the motor. It is the time
constant of an e-function.
Normally the motor is cooling down with a slower
time constant. Parameter τCis to be understood as a
factor. The cooling-down behaviour in the thermal
model proceeds with the time constant τCx τW. If
τC= 1 is selected, then heating and cooling-down
proceed at an identical speed in the thermal image.
5.4.3 t2x and t6x Minimal Trip Time
During the Starting Process.
With this parameter the fastest trip time during the start-
up phase is limited for the thermal image. If the se-
lected pick-up value k x IB is exceeded by two times
or six times, the characteristic breaks to definite time.
This prevents that a higher start current causes the
thermal image to overflow at the first instant. Normally
six times the value is selected. If not desired, the char-
acteristic can be operated without breaking by setting
EXIT.
5.4.4 Phase Undercurrent Element (I<)
Running-dry protection / V-belt split
The MRM3 trips if after a successful start the current
lies below the adjusted current threshold for a definite
time. Undercurrent is only active during mode
RUNNING. The undercurrent element is also blocked
if the measured current lies below the STOP threshold
(see chapter 4.1). EXIT is set, then this element is
switched off.
The time delay for the undercurrent element is set to
seconds.
Note:
The time delay must not be set shorter than the STOP
time, otherwise every time the motor is stopped, an
undercurrent trip occurs.
5.4.5 Phase Overcurrent Element (I>)
When adjusting the pick-up value for the phase over-
current element I>, an indicating value, referring to the
secondary rated current IN, is displayed. This element
is only active during mode RUNNING.
5.4.6 Trip Characteristics for the Phase
Overcurrent Element (I>+CHAR)
There are the following standard trip time characteris-
tics available (see 7.5:
DEFT - Definite Time (definite time
overcurrent protection)
NINV - Normal inverse
VINV - Very inverse
EINV - Extremely inverse
RINV - RI-Inverse
LINV - Long term Inverse
5.4.7 Tripping Time or Time Factor for the
Phase Overcurrent Element (I>+t>)
Normally, after change of the trip characteristics, the
tripping time or the time factor also has to be changed
accordingly. In order to avoid an unsuitable combina-
tion between trip characteristics and tripping time or
time factor, the following measures are initiated by the
MRM3:
::
:
The LED for adjustment of the tripping time or time fac-
tor (I> + t>) starts to flash after the trip characteristics
have changed. By this warning signal the operator is
reminded to adjust the tripping time or time factor to
the changed operational mode or trip time characteris-
tics. This warning signal keeps flashing until the trip-
ping time or time factor are re-adjusted. If re-adjust-
ment has not been done within 5 minutes (the time to
enable parameter setting), then the processor sets the
tripping time or time factor to the highest sensible
value (smallest possible tripping time ).

16 TB MRM3 07.01 E
When adjusting to the “Definite Time” trip characteris-
tic, the definite tripping time displayed is shown as
seconds (e.g. 0.35 = 0.35s). By pressing push-
buttons <+><-> this time can be changed step by step
in the range 0.04s – 260s
When adjusting to the “Inverse Time” trip characteris-
tics, the time factor (tI>) is displayed. This factor can
be changed also by push buttons <+><-> step by step
in the range 0.05 – 20.0.
If the tripping time or time factor are set to infinite long
(on the display “EXIT” is shown) then trip of the relay
overcurrent element is blocked. The
WARNING/ALARM function is still active. During this
time LEDs I> and t> are red.
5.4.8 Reset Mode for the Trip Characteris-
tics in the Phase Current Path
(I>+CHAR+t>)
In order to ensure that the trip function is reliable even
with repeated error pulses, each of them shorter than
the set tripping time, the RESET mode for the trip char-
acteristics can be changed over. With a setting of
“60s“ the elapsed tripping time is frozen and is only
reset after 60s faultless operation. Should another fault
occur within these 60s, the tripping time counter re-
mains in operation. With the setting “_ 0s“ the counter
is immediately reset when the fault current is inter-
rupted and it is restarted when the fault current has re-
turned again.
5.4.9 Phase Short-Circuit Trip (I>>) and
(I>>+Start)
The short-circuit element has two threshold values and
a common time delay. The first threshold value applies
for the mode RUNNING and the second one for
mode START.
Possible variations are:
•During the start procedure the existing inrush cur-
rent can be higher than the desired short-circuit
threshold during operation.
•It is also possible that the slip rings are put at risk
especially during the start procedure so that for
START a more sensitive adjustment is required than
for RUNNING.
•Both elements can be set to the same value so
there is no differentiation.
If it is set to EXIT then the respective element is
switched off.
Irrespectively of the selected trip characteristics for I>,
the short-circuit high-speed trip element I>> has a trip-
ping time which does not depend on the current. This
time applies for both elements I>>START and I>>RUNNING.
5.4.10 Negative Phase Sequence
Load unbalance can, for example, be caused by a
phase failure or fault in a one motor winding.
Load unbalances give rise to negative phase sequence
currents in the stator, causing odd harmonics in the sta-
tor winding and even harmonics in the rotor winding.
Especially the rotor is endangered by this because
asymmetric conditions mean additional thermal stress
for the rotor winding and eddy currents are induced in
the solid iron of the rotor which can cause destruction
of the metal structure or even melting of the metal.
Within certain limits and by observing the ultimate
thermal strength of the motor, load unbalance is per-
missible, though. The details given by the motor manu-
facturer mostly refer to the negative phase sequence
system and thus can be programmed directly.
According to the method of “Symmetric Components“,
a rotating three-phase system can be sectionalised into
a positive phase sequence system, negative phase se-
quence system and a zero phase sequence system.
The current in the negative phase sequence system is
the measure for the load unbalance quantity. The ef-
fective value of the current of the negative phase se-
quence system I2is calculated by the MRM3.
When setting the threshold value for the load unbal-
ance current I2> , the indicated value referring to the
rated current (IN). is displayed.
When adjusting the trip characteristics either « DEFT »
for “definite” trip characteristics is shown on the dis-
play or « INVS » for “inverse” trip characteristics.
5.4.11 Earth Fault Element (IE>)
The setting procedure outlined in chapter 5.4.5 ap-
plies here as well. The required value in the 0.01 x IN
– 2.00 x INrange can be set with push-buttons <+>
and <->.

TB MRM3 07.01 E 17
5.4.12 Trip Characteristics for the Earth-
Fault Element (IE>+CHAR)
When adjusting the trip characteristics one of the fol-
lowing 7 abbreviations is displayed:
DEFT - Definite Time (definite time over-
current protection)
NINV - Normal inverse (Type A)
VINV - Very inverse (Type B)
EINV - Extremely inverse (Type C)
RINV - RI-Inverse
LINV - Long-term inverse
RXID - Special purpose characteristics
The displayed text can be changed by push-buttons
<+><-> . By pressing <ENTER> the required trip
characteristics is selected. The allocated LED IE> is red,
the LED CHAR green.
5.4.13 Tripping Time or Time Factor for
the Earth Fault Element (IE>+t>)
The setting procedure outlined in chapter 5.4.7 ap-
plies here as well.
5.4.14 Reset Time for the Earth Fault
Element (IE>+CHAR+t>)
The setting procedure outlined in chapter 5.4.8 ap-
plies here as well.
5.4.15 Tripping Time for the CB Failure-
Protection (CB+t>)
This protection is activated after a protective trip and it
monitors if all phase currents have dropped within the
set time tCBFP to <2% x IN. If not, CB failure is detected
and the allocated relay triggered. (CBFP= Circuit
Breaker Failure Protection).
5.4.16 External Trip (delayed)
(Trip+t>)
Via the digital input A8/D8 an external trip with time
delay can be activated. Trip is initiated if the <signal
existed for at least the set time. The external trip func-
tion can be allocated to a relay.
5.4.17 Trip Blocking in case of Excessive
Phase Current (Trip+Block)
This function is important where power contactors are
used and they are not designed to disconnect high
short-circuit currents. In such a case no function of the
MRM3 must initiate tripping. The trip function is then
allocated to a preceding protective element (e.g.
fuse).
Trip blocking is activated as soon as the set current is
exceeded. When this threshold is undershot, all func-
tion are released again.
If the circuit breakers used are able to disconnect the
short-circuit current to be expected, the function is set
to EXIT.
5.5 Start Supervision
The MRM3 can offer two start supervision methods:
•Automatically by means of the thermal load
•By a limited number of starts per time interval
5.5.1 Duration of a Start Cycle (No.+Start)
AUTO
If this mode is selected, a start is always possible if suf-
ficient start reserves are available according to the
thermal image. This function operates dynamically on
the data of the previous starts (see chapter 4.1.1).
Time Adjustment
By this the interval of the permissible number of starts is
timed.
The number is defined in the next parameter.
EXIT
The element is de-energised.
5.5.2 Number of Starts per Cycle
(No.+Start)
This parameter is only visible if a time was selected
with the preceding parameter which defines the num-
ber of permissible starts during the respective interval.

18 TB MRM3 07.01 E
5.5.3 Start Blocking Time (Start+Block+t>)
This parameter is only visible if a time was selected
(chapter 5.5.1). It defines the time for a new start
when the number of starts per interval was exceeded.
The following is possible:
VARI
A new start is possible after the remaining time of the
interval has run down.
Time Adjustment (s):
Restarts are blocked for the adjusted time.
5.5.4 Maximal Start Time (Start+t>)
Exceedingly long acceleration can only be recognised
if the threshold k*IBis once overshot after the STOP
threshold was exceeded. The time meter for the max.
start time is activated upon exceeding of the threshold
k+IB. If the set time has elapsed and the current lies
(still or again) above the START threshold, the start
procedure is stopped. When mode RUNNING is rec-
ognised, this element is de-activated until the next start
attempt.
5.6 Interface Parameters
5.6.1 Adjustment of the Slave-Address (RS)
The Slave address can be adjusted in a range from 1-
32.
5.6.2 Adjustment of the Baud-Rate
(only for Modbus Protocol)
When the Modbus protocol is used for data transmis-
sion it is possible to adjust different transmission
speeds (Baud rates).
5.6.3 Adjustment of the Parity
(only for Modbus-Protocol)
For adjustment of the parity there are three options:
•“even“ = even parity
•“odd“ = odd parity
•“no“ = no check of the parity
5.7 Fault Recorder (FR)
5.7.1 Fault Recorder
The existing store can be utilised in two ways:
Not to be overwritten
Previous recordings will not be overwritten. When
there is no memory space left, further recordings are
not possible.
Overwrite
The latest fault incidents can always be called up; The
eldest recording is overwritten by a new one.
Parameter Mode Time per Record (s)
Adjustment* 50 Hz 60 Hz
S=1 overwrite 8.00 6.66
S=2 Not to be over-
written
8.0 6.66
S=3 overwrite 4.00 3.33
S=4 Not to be over-
written
4.00 3.33
S=7 overwrite 2.00 1.66
S=8 Not to be over-
written
2.00 1.66
* s = total no. of recordings
Table 5.2:
The storage zone of the fault recorder is designed as
ring buffer. In the example shown below storage of 7
fault recordings are possible (overwriting). The 8th
segment serves as buffer store.
Memory space 6 to 4 is used.
Memory space 5 is needed for temporary storage of
ongoing signals.
Figure 5.1: Partitioning of the store into 8 segments, for instance
This example shows that the store was used for more
than 8 recordings because store spaces 6, 7 and 8
are used. From this it follows that no. 6 was the eldest
recording and no. 4 the latest one.

TB MRM3 07.01 E 19
trigger occurence
recording duration
Tpre
[s]
Figure 5.2: General Set-Up of the Fault Recorder
Each of the storage segments have a fixed storage
time where the time before the trigger event can be
defined.
Via the RS485 interface the data can be read out by
means of a PC provided with HTL/PL-Soft4. The data
is graphically edited and represented. Binary tracks
are recorded additionally, e.g. activation and trip.
5.7.2 Number of Fault Recordings
The max. recording time is 16 s at 50 Hz or 13.33 s
at 60 Hz.
The max. number of recordings to be stored has to be
defined beforehand. There is the choice between (1)*
2, (3)* 4 and (7)* 8 recordings. Hence the existing
memory space can be used as follows:
(1)* 2 recordings for 8 s at 50 Hz and 6.66 s at
60 Hz.
(3)* 4 recordings for 4 s at 50 Hz and 3.33 s at
60 Hz.
(7)* 8 recordings for 2 s at 50 Hz and 1.66 s at
60 Hz.
* will be overwritten when a new trigger signal oc-
curs.
5.7.3 Adjustment of the Trigger Event
There is the choice between four different trigger
events:
P_UP (PickUP) Data saving begins when a general
activation is recognised.
TRIP Data saving begins when a general
trip is recognised.
A_PI (After Pickup) Data saving begins when the last acti-
vation threshold is undershot (recog-
nises, for instance, CB failure protec-
tion)
TEST Data saving is activated when push-
buttons <+> and <-> are pressed
simultaneously (immediately upon
pressing the buttons). For recording
time, the mode TEST is displayed.
5.7.4 Pre-Trigger Time (Tvor)
The time Tpre defines the period to be saved prior to
the trip event. This time can be set between 0.05 s
and the max. recording time (2, 4 or 8 s). With push-
buttons <+> and <-> the values can be changed and
with <ENTER> they can be saved.
5.8 Setting of the Clock
When date and time are set, the LED „!“ is on. The
following method is used:
Date: year Y=00
month M=00
day D=00
time: hour h=00
minute m=00
second s=00
Immediately when the supply voltage is applied the
clock starts with the respective date and time. The time
is buffered against short-term voltage failures (min. 6
minutes).
Note:
The window for setting the clock is behind the measur-
ing value reading. Access to the window via push-
button <SELECT/RESET>.

20 TB MRM3 07.01 E
5.9 Additional Functions
5.9.1 Blocking of the Protective Functions
Blocking of the protective functions
After voltage has been applied to blocking input
D8/E8, the intended reaction for each of the protec-
tive functions can be defined individually. (Observe
voltage adjustment !) See chapter 3.1.4
Setting Effect when voltage has been applied
to the blocking input
PR_B Complete blocking of the protective ele-
ment. Activation and trip are suppressed.
TR_B Blocking of trip elements.
The individual protective elements are
activated and this is signalled accord-
ingly, but there is no tripping.
BLOC Complete blocking of the protective ele-
ment. Activation and tripping are sup-
pressed. This is displayed if it is not dif-
ferentiated between PR_B and TR_B in a
parameter.
NO_B No blocking.
This element operates normal, it is not
blocked
Table 5.3: Adjustment Possibilities
Setting of parameters should be done as follows:
•To come to the blocking menu push-buttons
<ENTER> and <TRIP> are to be pressed at the
same time. The function being set is indicated by
LEDs.
•If necessary the blocking function can be changed
with <+> or <-> and saved with <ENTER>
Perhaps a password has to be entered.
•Proceed to the next function with
<SELECT/RESET>
•After selection of the last blocking function settings
for the 2nd parameter set can follow.
•For allocating the RESET function press push-button
<SELECT/RESET> again. (See next chapter).
Symbol Protective Function Default
Setting
Possible Settings LED/Colour
ϑ>Overload warning element NO_B NO_B ; BLOC ϑ> red
IB> Overload element NO_B NO_B ; PR_B ; TR_B IB>green
I< Undercurrent element NO_B NO_B ; PR_B ; TR_B I< red
I> Overcurrent element NO_B NO_B ; PR_B ; TR_B I> red
I>> Start Short-circuit element at start-up BLOC NO_B ; BLOC I>> red/Start green
I>> Short-circuit element PR_B NO_B ; PR_B ; TR_B I>> red
I2> Load unbalance element NO_B NO_B ; PR_B ; TR_B I2> red
IE> Earth current element NO_B NO_B ; PR_B ; TR_B IE> red
tCBFP CB failure protection NO_B NO_B ; BLOC CB green
Trip External trip NO_B NO_B ; BLOC Trip red
Table 5.4: Default Setting of the Blocking Functions