DV Power RMO30T User manual

RMO30T
W I N D I N G
OHMMETER
Manual
IBEKO POWER AB

2
RMO30T Contents
Contents
1 Introduction ...........................................................................................................................3
2 Safety Instructions.................................................................................................................3
3 Designated Use.....................................................................................................................4
4 Functionality..........................................................................................................................4
5 Description ............................................................................................................................7
6 Getting Started......................................................................................................................9
7 RMOWin-T5 Software .........................................................................................................18
8 Error Messages...................................................................................................................29
9 Technical Data ....................................................................................................................31
10 Accessories.........................................................................................................................32
Manufacturer Contact Information..............................................................................................32
Manual Version: RMO30T. MV.03.24
This Manual refers to the firmware version RT3-5.04
IBEKO POWER AB 2008
This Manual is a publication of IBEKO POWER AB, 181 33 Lidingö, Sweden.
All rights including translation reserved. Reproduction of any kind, e.g., photocopying, microfilming or storage in
electronic data processing systems, requires the explicit consent of IBEKO POWER AB. Reprinting, wholly or in
part, is not permitted.
This Manual represents the technical status at the time of printing. The product information, specifications, and all
technical data contained within this Manual are not contractually binding. IBEKO POWER AB reserves the right to
make changes at any time to the technology and/or configuration without announcement. IBEKO POWER AB is not
to be held liable for statements and declarations given in this Manual. The user is responsible for every application
described in this Manual and its results.
IBEKO POWER AB explicitly exonerates itself from all liability for mistakes in this Manual.
IBEKO POWER AB translates this Manual from its source language English into a number of other languages. Any
translation of this Manual is done for local requirements, and in the event of a dispute between the English and any
non-English versions, the English version of this Manual shall govern.

3
RMO30T Introduction, Safety Instructions
1 Introduction
This Manual contains helpful instructions on how to use RMO30T in a safe, proper and efficient way.
Following these instructions can help you avoid dangerous situations, repair costs and other miss
happenings due to incorrect operation. Furthermore it ensures the reliability and life cycle of your
RMO30T.
RMO30T must be used in observance of all existing safety requirements and regulations from
national/local standards for accident prevention and environmental protection.
Reading the RMO30T Manual alone does not exempt the user from the duty of complying with all
national and international safety regulations relevant for working with RMO30T.
2 Safety Instructions
Before operating RMO30T, please read carefully the following safety instructions.
It is not recommended that the RMO30T is used (or even turned on) without the understanding of this
Manual.
RMO30T should only be operated by trained and authorized personnel.
Rules for Use
• RMO30T should only be used when in a technically fit condition. Its use should be in accordance with
the safety regulations for the actual working site and application. Always be aware of the dangers of
high voltages and currents associated with this equipment and its environment. Pay attention to the
information provided in the Manual.
• RMO30T is intended exclusively for the application areas specified in ”Designated Use”. The
manufacturer and distributors are not liable for damage resulting from wrong usage. The user alone
assumes all responsibility and risk.
• The instructions provided in this Manual are considered part of the rules governing proper usage.
• Do not open RMO30T. All service and maintenance work must be performed by qualified
personnel.
Orderly Practices and Procedures
• The Manual should always be available on the site where the RMO30T is used.
• Before using RMO30T, all personnel (even personnel who only occasionally, or less frequently, work
with RMO30T) assigned to RMO30T should read the operations Manual.
• Do not undertake any modifications, extensions, or adaptations to the RMO30T.
• Use RMO30T in conjunction with original accessories only.
• Use both RMO30T and its original accessories for its designated use only.
Cleaning
To clean RMO30T, use a cloth dampened with isopropanol alcohol or water.
Operator Qualifications
• Testing with RMO30T should only be carried out by authorized and qualified personnel.
• Personnel receiving training, instruction, direction or education on the RMO30T should remain under
the constant supervision of an experienced operator while working with the test set and the test
object.

4
RMO30T Designated Use, Functionality
Safe Operation Procedures
• Hazardous voltages of up to 400V can occur inside RMO30T. Therefore, it is not permitted to open
RMO30T.
• Do not insert objects (e.g., screwdrivers, etc.) into the ventilation slots.
• Before putting RMO30T into operation, check the test set for any visible damage.
• Do not operate RMO30T under wet or moist conditions (condensation).
• Do not operate RMO30T when explosive gas or vapors are present.
• The serial interface of RMO30T should only have external devices connected that meet the
requirements for SELV equipment according to EN 60950 or IEC 60950.
• When setting up RMO30T, make sure that the air slots of the test set remain unobstructed.
• If RMO30T is opened by the customer, all guarantees are invalidated.
• If RMO30T seems to be functioning improperly, please contact the IBEKO POWER AB (refer to
section ”Manufacturer Contact Information”) after first checking the section Error Messages.
• Do not use RMO30T without the extra protective ground cables for RMO30T and winding connection.
Always establish this connection as the first one before you do any other connections, and separate
this connection as the very last one.
• Never open the measuring circuit while current flows as dangerous high voltage may occur. This
is indicated by the red discharge LED and the beeper.
Power Supply
• Supply RMO30T only from a power outlet that is equipped with protective ground.
• Instead of supplying RMO30T from phase – neutral (L1-N, A-N), it may also be supplied from phase
to phase (e.g., L1-L2; A-B). However, the voltage must not exceed 240V AC, please refer to the
section Technical Data.
3 Designated Use
The Winding Ohmmeter RMO30T is designed for measuring resistances of inductive test objects used in
the electric power industry or similar industries. It is employed for resistance measurement during
manufacturing, commissioning and testing of:
transformers,
on-load tap changers,
generators and electrical motors,
high current busbar joints,
cable splices.
Any other use of the RMO30T than the ones mentioned above is to be considered improper and will not
only invalidate all customer warranty claims but also exempt the manufacturer from its liability for repair
or exchange.
4 Functionality
4.1 Current Test
The RMO30T generates a filtered (true) DC current.
RMO30T test set can measure the winding resistance of any transformer; small or very large, single or
three phase, star, delta or zig-zag connected. There are two independent measuring channels which can
be used to simultaneously measure resistance of up to two windings at the same time.
Choose the test current so that the maximum value is obtained for the expected resistance (refer
to section 6.1 on page 12).

5
RMO30T Designated Use, Functionality
The inductance value of a transformer depends on the current injected in the windings. When the
transformer is saturated the inductance is minimized. A transformer is normally designed to reach
saturation when the current is 1,2 times the peak value of the no-load current. The no-load current is
normally in the range of 0,2% to 5% of the nominal winding current.
When measuring the DC resistance, the test current should be at least 1,2 times the no-load current of
the transformer. This is to ensure that the transformer core is saturated. Note also that the test current is
NOT to exceed approximately 10% to 15% of the nominal winding current.
Note: The Voltage sense measuring channels are automatically selected connecting measuring cables
to those channels.
At the start of each test a check of cable continuity is done. In case of open circuit, an alarm is activated,
and the error message is shown on the display.
The test is started by pressing the START button. The RMO30T injects current with a voltage as high as
60V. This ensures the test to be as short as possible and that the desired test current is reached faster.
When the current is stabilized, RMO30T measures the resistance of the test object. The test result is
displayed as R=U/I. During the testing period, a new result is shown on the display approximately each
second.
Tests could be finished or interrupted two ways:
- Pushing the STOP button,
- Automatically, after the selected time has expired.
In both cases, upon completion of the test, a measured value of the resistance is recorded to pre-
selected internal memory location.
Each time the Ωbutton is pushed, results of the resistance and the test current value are stored into the
internal memory of RMO30T, and memory location changes to the next one.
Minimum measurement time is 60 seconds.
By pushing the STOP button test could be completed at any time. When the STOP button is pushed, the
last measured result will remain saved in the internal memory.
After the selected test time has expired, the last result remains saved at selected memory location.
Note: Using RMOWin-T5 the results could be stored to a PC, where reading interval of results is
adjustable. Results will be shown in a table in Excel format with an option to perform additional edit and
graphic presentation.
Using RMOWin-T5 after the test in order to transfer the results from selected internal memory location to
a PC, will allow transfer of the last test result only.
When the measurement is complete, RMO30T starts discharging the energy from the inductance. During
current discharging, the red discharge LED is lit and the buzzer is ON. Discharge is complete when the
discharge LED and the buzzer are OFF.
Both, injection of current and discharging energy from the inductance is fully automatically regulated. An
intrinsically safe discharge circuit, with indicator, dissipates the stored magnetic energy rapidly after the
test.
Cooling of RMO30T is supported by a built-in fan that is automatically activated when the device is
turned on.

6
RMO30T Designated Use, Functionality
4.2 Tap Changer Test
The TapC menu offers a user friendly way of measuring winding resistance in tap changers.
RMO30T test set measures the winding resistance of individual taps of a power transformer’s tap
changer, and checks whether the On-Load Tap Changer (OLTC) switches without a discontinuity. In the
moment the tap is changed from tap to tap, the device detects the sudden, very short drop of the current
flow. A properly working tap changer differs from a malfunctioning one in a discontinuity during the
change, by the magnitude of the current ripple value. An interruption will result in a much higher ripple
value than a properly functioning tap changer.
Note: In TapC menu only Ch:1 is the active channel. Maximum test current selected in the TapC mode is
10A.
At the start of the test a check of cable continuity is performed. In case of disconnection, an alarm is
activated, and the error message is shown on the display.
Note: Using RMOWin-T5 in TapC menu the results could be stored to a PC. By pushing the Ωbuton a
resistance result and current ripple value are stored in internal memory location, and the memory
location is automatically increased by one.

7
RMO30T Description
5 Description
5.1 Front Panel Components
STOP button
Press to stop a test or stop the alarm buzzer.
START button
Press to start a test
Test parameters must be selected beforehand
Ωbutton
Press to measure the resistance current value.
Press to measure the resistance value in TapC mode
Green LED
• Lights continuously when RMO30T is turned on.
• Flashes when a test can be started.
• Flashes alternately with the red LED during a test.
Red LED
• Lights continuously in case of operational error.
• Lights continuously during discharging process.
• Flashes alternately with the green LED during the Current test.
• Flashes shortly during resistance measurement in the TapC test.
• Flashes alternately with the green LED during the TapC test.
Red LED - Discharge
• The red LED just above the red output connector remains lit until the accumulated energy of the
measured object is reduced to a harmless level
CAUTION
Within the period when the discharge LED lights it is prohibited to disconnect measuring cables.
The discharge diode could not be switched off by the STOP button.
Display
UP/DOWN buttons to select a
menu and set test parameters
LEFT/RIGHT buttons to
navigate in the active menu
ENTER button to confirm the defined test
parameters, Language, Time and Date
STOP button to stop a test, to
acknowledge the alarm buzzer
and return to the Cur
r
menu

8
RMO30T Description
5.2 Rear Panel Components
5.3 Setting RMO30T’s Language
To set RMO30T’s language, use the LEFT button, and then the UP buttons to select the Language
menu.
Move the cursor to the bottom line using the LEFT/RIGHT buttons, and select the language with the
UP/DOWN buttons.
Pressing ENTER to confirm, returns you to the Curr menu.
Pressing STOP to cancel, returns you to the Curr menu.
5.4 Setting RMO30T’s Time and Date
To set RMO30T’s internal time and date, use the LEFT button, and then the UP button to select the Time
menu.
Move the cursor to the position of your choice using the LEFT/RIGHT buttons, and change the value with
the UP/DOWN buttons.
Pressing ENTER to confirm, returns you to the Curr menu.
Pressing STOP to cancel, returns you to the Curr menu.
Earth/ground connector.
For protection against parasitic currents or voltages, always
connect RMO30T earth/ground connector to protective ground
(PE). Use only the original cable.
For safety reasons, always establish this connection as the
first one before you do any other connections, and separate
this connection as the very last one.
Ventilation
Figure 5-1:
The Language
menu
Figure 5-2:
The Time menu showing
RMO30T’s internal time
and date
Connector for mains power supply
Power switch
I In this position, RMO30T is connected to the
mains power supply.
0 In this position, RMO30T is separated from
the mains power supply with both poles.

9
RMO30T Getting Started
6 Getting Started
6.1 Current test
Connecting a Test Object to the RMO30T
Before you connect a test object to RMO30T, make sure that:
• The test object is disconnected or separated from its circuit in accordance with the national safety
regulations and is properly grounded to protective earth.
• RMO30T itself is properly grounded. To do so, connect the grounding screw on the back of
RMO30T’s to PE using a grounding cable.
• One end of measured windings is properly grounded.
• See example of a two channel setup in the figure below (6-1).
C A U T I O N
FOR SAFETY REASONS, ALWAYS ESTABLISH A CONNECTION OF THE DEVICE WITH
TEST OBJECT IN THE WAY AS DESCRIBED IN THE FIGURE 6-1.
DO NOT CONNECT MEASURING CABLES AFTER TEST STARTS.
DO NOT DISCONNECT ANY LEADS BEFORE THE LED DISCHARGE AND THE BUZZER
ARE OFF.
The Figure 6-2 shows simultaneous testing of both windings (high and low) on a single-phase
transformer. In such a way, it is possible to speed up the measurement when two channels are used to
test both windings of the transformer.
When performing a two channel measurement; connect the Current connection cable as in the
example below (Figure 6-2.) and outside the Sense leads.
Figure 6-1:
Connecting a test
object to RMO30T With RMO30T turned off, connect RMO30T to
the test object in such a way that the measuring
cables from the "Voltage Sense" sockets are
attached as close as possible to RX, and in
between the current feeding cables. That way,
resistance of both cables and clamps is almost
completely excluded from the resistance
measurement. Pay attention to polarity while
connecting measuring cables.
To maximize accuracy and measurement
repeatability; make sure that all clamps have a
good connection to the test object and avoid
any connection between Sense and Current
clamps.

10
RMO30T Getting Started
Testing of a Delta-delta winding resistance is usually a very time consuming procedure. This is because
the two windings resemble two closed loop inductors. When energy is brought into the inductors, this
energy (in the form of D.C. current) continually circulates within each winding. A method to quickly test
this configuration requires that both the high side and low side are connected in series with the Winding
Ohmmeter. By having these two windings in opposing polarity, the internal circulating currents settle very
quickly to obtain a balance, and discharge with the same speed. Even if only one side of the transformer
needs to be tested, connecting both high and low windings in series will speed up the test considerably.
On/Off
Connect the earth/ground lead first before doing any connections to the test object.
Connect the mains lead to a mains outlet 100V - 240V AC and turn on RMO30T with the power
switch on the back of the test set. The first shown on the display is the name of the product followed
by the instrument model type and the internal firmware version.
Figure 6-2:
Connecting a test
object to RMO30T
Figure 6-3:
Connecting a test
object to RMO30T

11
RMO30T Getting Started
Setting the Measurement Parameters
Directly after the first display RMO30T automatically changes to the Curr menu and the
green LED lights up.
Before a test can be started, the following needs to be defined in the Curr menu:
Test current; the following values can be chosen:
5 mA, 10 mA, 50 mA, 100 mA, 500 mA, 1A, 2A, 5A, 10A, 20A, 30A,
Memory position, 00-99
Test duration time can be set between 5 minutes and 60 minutes depending on test current,
see table under “Measurement parameters” (section 6.5).
In the Curr menu, define a test current for the test (here 10A). To do so, set the value of your choice by
means of the UP/DOWN buttons. Define the memory position (here m:23).
Using button RIGHT move the cursor to the memory location position, and using UP/DOWN select desired
memory position to which obtained results would be saved. Once the test is completed (either due to
time expiration or when pushing the STOP button) the last measured result will remain registered in
RMO30T, and the memory position is automatically switched over to the next memory position. The
result can be recalled later by selecting that particular position number.
Using RIGHT button move the cursor to the test duration position, and using UP/DOWN buttons select
desired value.
Measuring with RMO30T
Before a test can be started, test current, memory position and the test duration time need to be defined
using the Curr menu.
Once these parameters are defined, press ENTER to change to the Ready state.
The Ready state displays the selected test current and its duration is defined. If one of these values has
to be changed, press STOP to return to the Curr menu.
The flashing green LED indicates that RMO30T is now ready to start the test. Press the START
button to run a test. At the start of the test, a cable connection check is done. In case of e.g. a
disconnection, an alarm is activated and the error message is shown on the display.
During the test, both the green and the red LEDs flash alternately and the buzzer beeps. When the
current is stabilized, RMO30T starts the measurement of the test object resistance.
The display shows test current (here 9,98A) and the effective value of the measured resistance (here
789,1mΩon channel 1 and 788,9mΩon channel 2). The time remained until the end of test procedure is
also shown on the display (here 12s).
Test could be completed in two ways:
- Pushing the STOP button,
- Automatically after the selected time has expired.
Figure 6-4:
The Curr menu
Test current Memory position
Test duration time
Menu name
Figure 6-5:
The Ready state
before the test
Figure 6-6:
The Curr menu
during the test
Time

12
RMO30T Getting Started
When the test is finished either because selected time has expired or the STOP button is pressed,
the RMO30T switches to the Res menu and starts current discharging process. During current
discharging, the discharging LED lights and the alarm beeps.
Discharge is completed when LED discharge and the buzzer are OFF. Also, during that period
“Discharging” message is shown on the display. During discharging process it is not possible to
start another measurement.
Once the test is completed the last measured result will remain registered at a selected memory location
(00-99 memory locations).
Discharge Current
The voltage at the RMO30T output generation is immediately stopped, but current still flows, because of
the inductivity of test objects.
Because of the enormous amount of energy that can be stored in a magnetic field, precautions should
be taken before disconnecting the test leads from the transformer that is under test. Never remove the
leads during the testing process and always allow enough time for the transformer being tested to
completely discharge. Large transformers can require several minutes to discharge.
C A U T I O N
DO NOT DISCONNECT LEADS BEFORE “DISCHARGING” MESSAGE IS DISAPPEARED
FROM THE DISPLAY.
Note:
Using RMOWin-T5 the results could be stored to a PC, where reading interval results is adjustable.
Results will be shown in a table in Excel format with an option to perform additional edit and graphic
presentation.
Using RMOWin-T5 after the test in order to transfer the results from selected internal memory location to
a PC will allow transfer of the last test result only.
Measurement parameters
Typical accuracy given in the table below is valid if the maximum possible current is used.
Range Test
Current
Nominal
Resistance
Full Range
Display
Resolution
1 30A 1mΩ999,9µΩ0,1µΩ
2 30A 10mΩ9,999mΩ1µΩ
3 30A 100mΩ99,99mΩ10µΩ
4 30A 250mΩ250,0mΩ0,1mΩ
5 30A 750mΩ750,0mΩ0,1mΩ
6 20A 1,25Ω1,250Ω1mΩ
7 10A 2,5Ω2,500Ω1mΩ
85A 5Ω5,000mΩ1mΩ
92A 10Ω9,999Ω1mΩ
10 1A 15Ω15,00Ω10mΩ
11 500mA 25Ω25,00Ω10mΩ
12 100mA 100Ω99,99Ω10mΩ
13 50mA 200Ω199,9Ω0,1Ω
14 10mA 1kΩ999,9Ω0,1Ω
15 5mA 2kΩ2000Ω1Ω
The highest resolution of the reading is always displayed; resistance range selection is performed
automatically and therefore is not necessary to be set by the operator.
Figure 6-7:
The Res menu
showing the test results

13
RMO30T Getting Started
Accuracy
Typical accuracy of RMO30T is ±(0,1% rdg + 0,1% FS). This accuracy is valid if the maximum possible
current is used. Always try to use as high current as possible, but to avoid the risk of heating the winding,
it is recommended not to exceed from 10 % to 15 % of the nominal current of transformer. It is important
to get a good connection between clamps and the connecting point on the test object to achieve stable
and accurate test results.
Viewing the Test Results
Once a test is finished, RMO30T automatically changes to the Res menu to display the test results.
6.2 Tap Changer test
Using RMO30T’s Tap Changer (TapC) menu the winding resistance of individual taps of a power
transformer’s tap changer can be measured. Also it can be used to control the transformer tap changer.
This is a user friendly way of winding resistance measurement and tap changer control, since automatic
measurement is possible with no need to remove the current between each tap change. During
switching the inputs of the instrument are protected to avoid damage that could occur should a tap
changer prove to be faulty during testing.
From the Current outputs, RMO30T injects a constant current into the power transformer. From this
current value and the voltage measured, the winding resistance is calculated. An interruption caused by
a defective tap changer results in a comparatively high measured values of current ripple.
Setting the Measurement Parameters
Turn on RMO30T with the power switch on the back of the test set. The display shows the Curr
menu and the green LED lights up. Press button LEFT and using UP button go to the TapC menu.
Figure 6-8:
The Res menu
showing the test
results
Test current
Memory position that holds
the results
Measured resistances of the test objects
Figure 6-9:
Connecting a test
object to RMO30T
and RMOWin-T5
Figure 6-10:
The TapC
m
e
n
u
Test current Memory position
Time
Menu name
Active channel

14
RMO30T Getting Started
In the TapC menu, define a test current for the test (here 10A).
To do so, set the value of your choice by means of the UP/DOWN buttons. In the TapC menu of
RMO30T, current output value is rated continuously at 10A or less. Define the memory position (here
m:87). Using button RIGHT move the cursor to the memory location position, then using UP/DOWN select
desired memory position to which obtained results would be saved.
By pushing the Ωbutton, resistance and current ripple measured results will remain registered in internal
memory of RMO30T, and the memory position is automatically switched over to the next memory
position. These results can be recalled later by selecting that position number.
Note: Only Ch:1 (left channel) is active channel.
Measuring with RMO30T
Before a test can be started, test current and memory position need to be defined using the TapC menu.
Once these parameters are defined, press ENTER to change to the Ready state.
The Ready state displays the selected test current and memory location. If one of these values has to be
changed, press STOP to return to the TapC menu.
The flashing green LED indicates that RMO30T is now ready to start the test. Press the START
button to run a test. At the start of the test, a cable connection check is done. In case of e.g. a
disconnection, an alarm is activated and the error message is shown on the display
During the period of current stabilization, both the green and the red LEDs flash alternately, buzzer
beeps and message “WAIT” is shown on display.
When the current is stabilized, press the OMEGA button to start the resistance measurement of the Tap
Changer starting position.
During the resistance measurement the red LED flashes shortly and beeper sound is speeded up.
The display shows test current (here 9,97A) and the value of the measured resistance (here 704,2mΩ).
The value of the resistance is displayed and after 5 seconds it disappears. The memory position is
automatically switched over to the next memory position and device is ready to record the current ripple.
Change the Tap Changer position to the next tap by pushing the "Up" or "Down" button of the tap
changer control. Because the resistance is changed, current will be unstable and RMO30T will sample
and hold the largest measured current ripple that occurred in the actual measuring cycle. It is indicated
as Δ(%) with reference to the test current.
The test current has changed (here 9,93A). Display shows the new value of test current and the value of
the current ripple (here 4,6%). At the moment the test current on the display is stable, press the OMEGA
Figure 6-11:
The Ready state
before the test
Figure 6-13:
The TapC menu during
the resistance test
Figure 6-12:
The TapC
menu during current
stabilization
Figure 6-14:
The TapC menu,
memory position is
increased for one

15
RMO30T Getting Started
button to start resistance measurement in the new position of Tap Changer. New resistance value is
displayed (here 719,3mΩ).
The memory position is automatically switched over to the next memory position. Repeat this procedure
as often as needed until the results for Δand R are obtained for all Tap Changer positions.
Test is completed pushing the STOP button.
The voltage at the RMO30T output generation is immediately stopped, but current still flows,
because of the inductivity of test objects.
When measurement is completed (after pressing the STOP button) RMO30T switches to the TapC
menu and starts current discharging. During the current discharging process, the discharging LED
lights and alarms beeps.
Discharge is completed when LED discharge and the buzzer are OFF. Also, during that period
“Discharging” message is shown on the display. During discharging process it is not possible to
start another measurement.
A properly working tap changer differs from malfunctioning one in a current discontinuity during the tap
change, by the magnitude of the current ripple value. A discontinuity will result in much higher current
ripple value (99 % or 100 %) than a properly functioning tap changer.
Note: Current ripple value depends on the construction of the tap changer. It is recommended to
compare current ripple values between each other got on one transformer. Also, it is recommended to
compare current ripple results on one transformer with results from some previous test in order to follow
conditions of that tap changer.
Figure 6-17 shows indication about possible tap changer bad conditions during the change from tap to
tap.
If current circuit is opened during the change from tap to tap, message „Discontinuity“ will be shown on
the display, red LED will light and buzzer will beep continuously. Discharging process starts.
Discharge Current
The voltage at the RMO30T output generation is immediately stopped, but current still flows, because of
the inductivity of test objects.
Because of the enormous amount of energy that can be stored in a magnetic field, precautions should
be taken before disconnecting the test leads from the transformer that is under test. Never remove the
leads during the testing process and always allow enough time for the transformer being tested to
completely discharge. Large transformers can require several minutes to discharge.
C A U T I O N
DO NOT DISCONNECT LEADS BEFORE “DISCHARGING” MESSAGE IS DISAPPEARED
FROM THE DISPLAY.
Figure 6-16:
The TapC menu during
discharging
Figure 6-15:
The TapC menu
during the test
Figure 6-17:
The TapC menu
showing much higher
current ripple value
Figure 6-18:
Message
"Discontinuity"

16
RMO30T Getting Started
Note:
Using RMOWin-T5 the results could be stored to a PC, where reading interval results is adjustable.
Results will be shown in a table in Excel format with an option to perform additional edit and graphic
presentation.
Using RMOWin-T5 after the test in order to transfer the results from selected internal memory location to
a PC will allow transfer of the last test result only.
Using RMOWin-T5 software it is possible to draw a graph which represent dynamic resistance during the
change from tap to tap (refer to section 7.4 on page 20).
6.3 Viewing Results of Previous Tests
RMO30T stores up to 100 test results. They can be viewed using the Mem menu at memory positions
from 0 to 99.
Go to Mem menu using LEFT, and then pressing the DOWN button.
Selecting a memory position on the Mem menu displays:
• the current fed into the test object,
• the memory position of these results,
• the test object’s measured resistance R1 (left channel) or R2 (right channel),
• the test object’s measured results R (resistance) or Δ(current ripple),
• the date or the time, of this particular test.
To view the measured resistance R2 rather than the resistance R1, position the cursor on the first letter
of the Mem menu (here M), and use the LEFT button to toggle between resistance R1 and R2 or
between R and Δ.
To view the creation date of the test rather than the time, position the cursor on the latest number of the
memory position (here 3), and use the RIGHT button to toggle between date and time.
6.4 Deleting Results of Previous Tests
In the Mem menu, press ENTER.
Press ENTER once more to delete all saved measurements from the memory positions. Press STOP to
leave the Mem menu without deleting any measurements.
Figure 6-19:
The Mem menu
showing the previously
saved test results
measured in Curr
mode saved in memory
position 23
Figure 6-21: The Mem menu
showing an option to
delete all saved
measurements from the
memory positions
Figure 6-20:
The Mem menu
showing the previously
saved test results
measured in TapC
mode saved in memory
position 93

17
RMO30T Getting Started
6.5 Duty Cycles
During tests, RMO30T generates a high DC current that heats up the test set. To prevent RMO30T from
overheating, certain duty cycles apply depending on the test current used.
Cooling time between two measurements is proportional to test duration time.A built-in control prevents
skipping these cooling times. If you try to start a test within the cooling period, the display shows "Wait"
and a timer counting down. After the cooling period has passed, start a new test using the set test
parameters by pressing the START button.
C u r r e n t T e s t
Test current
(A)
Maximal test
duration time (min)
Cooling time for
maximal test
duration time (min)
5mA, 10mA,
50mA,100mA, 500mA,
1A, 2A, 5A, 10A
60 0
20A 40 5
30A 20
5
Table 6-23:
Cooling time
between current
tests

18
RMO30T RMOWin-T5 Software
7 RMOWin-T5 Software
RMOWin-T5 is a Windows program for working with Winding Ohmmeters RMO30T. It enables the two-
way communication RMO30T to a PC over the USB. Microsoft Office Excel program must be installed on
the PC.
RMOWin-T5 supports the following functions:
- Controlling and starting RMO30T when the tests are performed from the PC; the results could be
stored to PC; results reading interval is adjustable,
- Transfer of test parameters from the local RMO30T memory to the PC with the possibility of writing the
notes on objects being measured, and appropriate comments.
Note: Using RMOWin-T5 software, a device RMO30T must be operated only from the RMOWin-T5.
Data transferred from RMO30T can be:
- Displayed in the form of tables,
- Downloaded as an Excel file.
Every test reading parameter contains:
- The memory location,
- The date and the time of the test,
- The real test-current,
- The measured resistance values,
- The measured voltage values,
- The measured ripple values,
- The name of the object (tested device) and the useful comments.
7.1 The minimum system requirements
Processor : Recommended > 500MHz
Memory : min 32Mb
Operating system : 95/98, NT, 2000, XP
The hard disk space : > 10Mb
7.2 RMOWin-W installation
To install the RMOWin-T5 software do the following:
- Insert the RMOWin-T5 installation CD into the CD-ROM drive,
- Click on ”Start”,
- Click on ”Run”,
- Click on ”Browse”,
- Select the CD-ROM drive,
- Highlight the ”RMOWin-T5.EXE”,
- Click on ”Open”,
- Click on ”OK”,
- Follow the instructions displayed on the screen,
- When the installation process has been finished - exit the program.

19
RMO30T RMOWin-T5 Software
7.3 Starting RMOWin-T5
Connect the USB port of the RMO30T Winding Ohmmeter and the PC, using a serial cable.
Turn RMO30T on.
Start RMOWin-T5:
- Click on ”Start”,
- Click on ”Programs”,
- Click on ''RMOWin-T5’’,
or duble click at icon on the desktop.
The look of the RMOWin-T5 main menu is shown in the following illustration.
If the ”Communication” field displays the green led-diode and the sign ”ON” is lit, the communication has
been established and the program is ready to be used.
Now the RMO30T can be controlled from the PC.
Clicking with the mouse on any key of the keyboard has the same effect as pressing the keys on the
RMO30T.
In case that the green led diode is not lit in the “Communication” window, i.e. the red led diode is lit, it is
necessary to check the following:
- Is the green led diode on the RMO30T lit?
- Is the RMO30T signaling any error?
- Is the serial cable connected tightly?
It is strongly recommended to write the information in the columns ”Object”, ”Code” and ”Comments” for
better systemization of the saved results.
The new test moves previous test results down so the first line represents the last performed test.
The way to measure the resistance is described in details in the RMO30T Manual.
If a user wants to analyze these results later, it should be saved on the hard disk. The table is going to
be saved as an Excel file, so it can be later used with all Excel functions.

20
RMO30T RMOWin-T5 Software
7.4 Graphic function
Using a PC together with RMO30T device in the Tap Changer mode it is possible to conclude about tap
changer conditions analyzing a graph which represents dynamic resistance during tap changes.
Figure above shows connections between a PC and RMO30T.
After all connections are properly done and RMOWin-T5 is started, chose TapC menu by clicking with
the mouse on the RMOWin-T5 buttons LEFT and then UP.
Note: Using RMOWin-T5 software, a device RMO30T must be operated only from the RMOWin-T5
Note: Before the beginning of the test set tap changer in the first or the last tap changer position.
Graphic function is available as on-line or off-line mode. Using on-line mode, test current value during
the transition from tap to tap is shown on the graph.
The on-line mode Graph control window shows information about current and next tap changer
positions. This information is not shown in the off-line mode.
In the off-line mode saved files containing graph data are opened.
Graph control window contains options and commands to control graph display. Graph is displayed in
separate window, where user can zoom in and zoom out interesting parts of the graph. Test current
values are shown on the vertical axis, and tap transitions are shown on the horizontal axis. Two markers
are available for measuring time difference, test current difference and current ripple between two
positions on the graph.
Also, in the on-line mode there is OMEGA button used to measure static resistance in the current tap
changer position. This is not available in the off-line mode.
After pressing ENTER button, fulfill dialog box Tap Changer Settings with all necessary information about
the tap changer.