Application Note
Products:
MonitorPro
Notes:
Insulation resistance testing via the MonitorPro when using a soft starter or VFD.
AN24-2
Date:
12-Aug-2003
Author:
Steve Carson
Insulation Resistance Testing via the MonitorPro
This application note can show you the easy way to protect your VFD’s while still performing insulation
resistance tests on the motors.
1
2
Application Overview
•
Variable Frequency Drive (VFD) is controlling the motors.
•
The Insulation Resistance Tester (IRT) function is required from the MonitorPro.
•
Under a normal setup, the IRT will be performed immediately upon the Pump Controller stopping the
motor. This may damage the VFD by applying a voltage to it’s output, or false readings may be
obtained if the VFD is still driving the output when the insulation resistance is measured, e.g. for a DC
brake or a ramp-down.
•
The Level Activated Digital Output from the Pump Controller is used to switch off the VFD before the
Pump Controller tries to stop the motor with the Pump output relay, so that when the IRT is performed
(as the pump controller thinks the motor is stopping), the VFD has already been stopped for a period of
time.
•
An extra contactor can be installed to isolate the VFD from the IRT.
Application Solution
• Pump 1 output and Level Activated Digital Output 1 are wired in series, and the combination of Pump
1 AND “Above Level” enables the VFD. (Pump 2 output also in series with a second Level Activated
Digital Output, to enable VFD 2)
• Level Activated Digital Output is programmed as Energize above level, and programmed to the same
level as the Pump deactivation level.
• The Pump Deactivation Time will determine the delay between the VFD stopping and the IRT being
performed.
• The VFD will be switched off while the Monitor Pro thinks the pump is still running. For this application
to work, the undercurrent alarms should be disabled on the MonitorPro, or the time delay to trip an
undercurrent alarm should be set to greater than the pump deactivation delay.
• As an additional extra, a contactor can be placed between the VFD and the motor, so that the VFD is
isolated from the IRT.
AN24-2.doc
8 July 2005
Page 1 of 7
Application Note
Products:
MonitorPro
Notes:
Insulation resistance testing via the MonitorPro when using a soft starter or VFD.
3
AN24-2
Date:
12-Aug-2003
Author:
Steve Carson
Hardware
• A MonitorPro and either an MT2PC or an MT3PC are the only intelligent devices that are required (2
digital outputs are needed for the Contactor option, so if you are using an MT3PC, you will loose one
Level Alarm.)
• An extra contactor per pump can be used to isolate the VFD from the Insulation Resistance Test.
• An isolating relay per VFD is required, as the one output point from the Pump Controller will be
controlling both the Contactor and the VFD.
• A 240VAC supply (typical – may vary according to contactors) suitable for driving the contactor and
isolation relays is also required. The coils on the contactor and VFD digital inputs isolating relay must
be the same voltage.
4
Wiring
It is assumed that:
• The VFD’s require a clean contact between “Enable” and “GND” to enable the motor.
• As the contactors on the output of the VFD’s will typically be rated a very large currents, it is assumed
that the coil voltage for these contactors is large (such as 240VAC), and this voltage is available from
the switchboard.
Note:
4.1
The relays are all fitted with Contact Spike Suppressors, and for these RC suppressors to be
effective, the Active voltage must be connected to the A1, B1, H1, J1, K1, M1 and S1 terminals
for each relay and the loads must be connected to the A2, B2, H2, J2, K2, M2 and S2 terminals.
Required Connections per Motor
• External voltage supply for contactors (e.g. 240VAC) connected to Pump 1 Enable COM (A1).
• Pump 1 Enable NO (A2) connected to both Digital Output 4 COM (S1) and to VFD 1 output contactor.
• Digital Output 4 NO (S2) connected to isolating relay.
• Outputs of isolating relay connected to VFD 1 GND and Enable.
• MonitorPro MEGGER output MA connected to Pump 1 phase 1, on the pump side of the contactor.
• These connections are then repeated for Pump 2 Enable, Digital Output 5, VFD 2, Contactor 2, and
MB.
AN24-2.doc
8 July 2005
Page 2 of 7
Application Note
AN24-2
Products:
MonitorPro
Notes:
Insulation resistance testing via the MonitorPro when using a soft starter or VFD.
Date:
12-Aug-2003
Author:
Steve Carson
The wiring diagrams on the following page show the required connections per motor, as described above.
Multitrode MT2PC
A
Pump 1 Enable Digital Output 4
N
A1
A2
S1
S2
Digital Output 5 Pump 2 Enable
M2
M1
B2
B1
Contactor
Contactor
VFD 1
Enable
N
VFD 2
Enable
N
Pump 1
Pump 2
GND
GND
N
Multitrode MonitorPro
MA
Megger Output 1
Megger Output 2
MB
Figure 1 – Wiring Diagram with VFD Isolation Contactors included.
Figure 2 – Wiring Diagram without VFD Isolation Contactors.
AN24-2.doc
8 July 2005
Page 3 of 7
Application Note
Products:
MonitorPro
Notes:
Insulation resistance testing via the MonitorPro when using a soft starter or VFD.
AN24-2
Date:
12-Aug-2003
Author:
Steve Carson
The back panels of the MonitorPro, MT2PC, and MT3PC are shown below for terminal locations.
Figure 3 - MultiTrode MonitorPro back panel showing terminal connections.
Figure 4 - MultiTrode MT2PC back panel showing terminal connections.
Figure 5 - MultiTrode MT3PC back panel showing terminal connections.
AN24-2.doc
8 July 2005
Page 4 of 7
Application Note
Products:
MonitorPro
Notes:
Insulation resistance testing via the MonitorPro when using a soft starter or VFD.
5
AN24-2
Date:
12-Aug-2003
Author:
Steve Carson
Precautions
The MonitorPro Insulation Resistance Test will emit 500VDC for approximately 10-15 seconds. If this
could damage the VFD, it is recommended that the contactors be installed to isolate the VFD’s from the
Insulation Resistance Test.
6
Programming
Before you program the devices, you should gain a basic understanding of how this application is being
implemented. The intended run-down sequence as the well is emptied will proceed as follows:
1.
The well reaches the low set point. The motor and the Level Activated Digital Output are both
programmed to this level.
2.
The low Level Activated Digital Output switches off immediately, disabling the VFD’s.
3.
The VFD’s may now ramp down or apply a DC brake.
4.
After the Pump 1 Deactivation delay, the Pump Outputs are disabled, which will open the contactor
between the VFD and the motor, isolating the VFD’s from the IRT.
5.
As soon as Pump 1 is deactivated by the MTxPC, the IRT is performed.
6.1
Important Notes
1.
The Level Activated Digital Output On time must be programmed to equal to or (preferably) greater
than the Pump 1 Deactivation Delay, otherwise the VFD will be re-enabled during the pump
deactivation period, and so will be active when the pump is stopped and the IRT is performed.
2.
The time delay before tripping an undercurrent alarm on the MonitorPro should be set to greater
than the Pump Deactivation Delay, so that the MonitorPro does not trip an undercurrent alarm during
the pump ramp-down period (i.e. during the Pump Deactivation Delay).
3.
The Digital Output must be programmed to Normally Closed, so that the VFD is enabled until the
alarm occurs.
4.
The Level Activated Digital Output is referred to in some parts of the manual as the “Well Washer
Output”, with the corresponding “Well Washer Activation Level” and “Well Washer Maximum Run
Time”. This output is referred to as such as this is the normal use of this output. This application
uses the Well Washer Output as a Level Activated Output, and so the parameters for the “Well
Washer” are actually controlling the operation of the Level Activated Digital Output.
AN24-2.doc
8 July 2005
Page 5 of 7
Application Note
AN24-2
Products:
MonitorPro
Notes:
Insulation resistance testing via the MonitorPro when using a soft starter or VFD.
6.2
Date:
12-Aug-2003
Author:
Steve Carson
Set up the Levels & Alarms on the Pump Controller
1.
Set up the pump activation and deactivation levels in the MTxPC in accordance with the MTxPC
manual
2.
Set up the Electronic Dip Switches in the MTxPC to program the Level Activated Digital Output, as
follows:
3.
For an MT2PC, set the following EDS’s as shown:
EDS#
4.
Description
Required Setting
54
Digital Output 4 Source
60 = Level Activation
55
Digital Output 5 Source
60 = Level Activation
59
Digital Output 4 NO/NC
On = N/C
60
Digital Output 5 NO/NC
On = N/C
61
Level Activation Trip Point
Same as Pump 1 Stop Level
62
Level Activation Run Time
Longer than Pump 1 Deactivation Delay
63
Washer Interstart Period
Off
64
Washer Maximum Off Time
Off
For an MT3PC, there is no Digital Output 5, so Digital Output 2 will have to be used. This will
remove the Low Level Alarm ‘Alarm 2’. To set up the MT3PC, set the following EDS’s as shown:
EDS#
6.3
6.3.1
AN24-2.doc
Description
Required Setting
52
Digital Output 2 Source
60 = Level Activation
54
Digital Output 4 Source
60 = Level Activation
57
Digital Output 2 NO/NC
On = N/C
59
Digital Output 4 NO/NC
On = N/C
61
Level Activation Trip Point
Same as Pump 1 Stop Level
62
Level Activation Run Time
Longer than Pump 1 Deactivation Delay
63
Washer Interstart Period
Off
64
Washer Maximum Off Time
Off
Set up the Insulation Resistance Tester on the MonitorPro
Enter the menu structure of the MonitorPro
by pressing “ENTER”, then entering
security passwords and job numbers as and
if required, then select the “STATION
SETUP” menu.
8 July 2005
MAIN MENU
FAULTS
HISTORY
SECURITY SETUP
STATION SETUP:
Supply faults
->Motor Protection
Flow Settings
->STATION SETUP
:COMMS SETUP
:GENERAL SETUP
Inputs/Outputs
Display Setup
Defaults Reset
Page 6 of 7
Application Note
AN24-2
Products:
MonitorPro
Notes:
Insulation resistance testing via the MonitorPro when using a soft starter or VFD.
6.3.2
6.3.3
Date:
12-Aug-2003
Author:
Steve Carson
Enter the “Motor Protection” sub-menu,
MOTOR PROTECTION MENU
->General
Pump 3
Pump 2
Copy Pump1 to Pump3
Pump 2
Copy Pump1 to Pump3
Then, enter the “General” sub-menu
MOTOR PROTECTION GENERAL
1/2
Motor Insuln Fault :->Enabled
Level (MOhm)
:05.0
Test Frequency
:All Pumps Stopped
6.3.4 To turn the Insulation testing function on, set the “Motor Insuln Fault” to “Enabled”.
6.3.5 At the “Level” line, enter the insulation resistance level below which the MonitorPro should return a
failed test. This value is entered in Mega-ohms (MΩ). If a motor fails a test, it will be locked out,
and will not be available for use. Although the legal limit in Australia is 1MΩ, we recommend a
much higher value, such as 5MΩ, to predict faults earlier, before they become a problem.
6.3.6 The test frequency will determine how often the Automatic test is performed. This can be daily,
weekly, or when all the pumps are stopped. If a daily (or weekly) frequency is selected, the test will
be performed upon the next motor stop 24 hours (or 7 days) after this menu is exited. If “All Pumps
Stopped” is selected, the insulation resistance test will be performed every time the motors stop.
This is the optimal time to perform the test as the motors are at their operating temperature. For
this application, the Test Frequency should be set to “All Pumps Stopped”.
MOTOR PROTECTION: GENERAL
Reset Mode
:->Auto - 1min
Immediate Test
:Test Now
2/2
6.3.7 Pressing down will select the next screen. The Reset Mode will determine how the motor will be
brought back into service in the event of a failed insulation resistance test. If an “Auto” setting is
selected, after the nominated time the motor will be retested and if it passes the test, will be reenabled. A “Manual” reset mode means that the motor will be locked out until the fault is manually
reset by pressing the reset button on the front of the Pump Controller. As a failed insulation
resistance test is a serious problem, we recommend that the Reset Mode be set to “Manual”.
6.3.8 Pressing, “Enter” while the arrow is pointing at “Test Now” will initiate an insulation resistance test
on all connected motors. Note that this test will be performed regardless of the status of the motors
according to the Pump Controller. If a motor is running, or the VFD or soft starter is injecting any
sort of power or signal into the motor (e.g. slowing down or DC brake) when the test is performed,
incorrect readings may be obtained. When the test is complete, the MonitorPro will return to the
main display. Pressing the down arrow once will show the results of the insulation resistance test.
MOTOR PROTECTION MENU
General
Pump 3
Pump 1
:Copy Pump1 to Pump2
Pump 2
:Copy Pump2 to Pump3
7
Conclusion
The above procedure has set up the IRT for Pump 1 only. The easiest method of programming the
remaining pumps is to copy the setup from pump 1 to the other pumps. This is done by selecting the
“Copy Pump1 to Pump2” or “Copy Pump1 to Pump3” options from the Motor Protection Menu, as shown
above, then pressing “Enter”. This menu is accessible from the “Station Setup” menu, as entered in
Steps 6.3.1 and 6.3.2.
Visit http://www.multitrode.com/ for the latest information
AN24-2.doc
8 July 2005
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