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Old July 8th, 2019, 02:13 PM   #1
neilm
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Powerflex 753 vfd fault

Hello everyone,

We are using a Powerflex 753 VFD to control a motor which lifts and descends loads. The drive goes into fault code 12 (HW Overcurrent) and code 36 (SW Overcurrent) multiple times while its descent in the loaded condition. The drive does not go into fault when-
1. It ascends or descends in no load.
2. Ascends in load condition.
Therefore the fault occurs only in one direction under loaded condition.

I have google searched and tried changing a few parameters [Parameter 43 (Flux Up Enable) and Parameter 44 (Flux Up Time), Parameter 70 (Autotune) and Parameter 621 (Slip RPM at FLA) to 0] but it didn't affect the faults.

Any ideas why? Any solutions?
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Old July 8th, 2019, 10:19 PM   #2
_Dock_
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Lots of things at play here. We need more information.

Brake? And how is it controlled?
Namplate rating and does it match your parameters?
How are you giving the run and direction command? Ethernet?
Do you have a braking resistor?

Basically the drives is seeing a massive current load which could be something really complex or something stupid simple. A misinterpretation of an implied decimal could be the issue and a few key strokes could fix it. Or, it could be much more complex.

Attach the ccw file and the motor namplate.

Last edited by _Dock_; July 8th, 2019 at 10:22 PM.
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Old July 8th, 2019, 10:53 PM   #3
willxfmr
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If it were me, I would lower the speed during the descent. It sounds to me like you have too much load traveling too fast.

Bubba.
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Old July 8th, 2019, 11:35 PM   #4
psychosunshine
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Can you watch the motor current on the keypad during the descent? That should paint a good picture as to what's going on there.


Is there a gearbox?
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Old July 9th, 2019, 07:48 AM   #5
neilm
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Motor specs

We use the following Brake controlled 2HP motor:
https://www.toshiba.com/tic/motors-d.../0024XDSC44A-P

I will try right now to reduce the output frequency and see its effect on the faults.
The run (forward or reverse) command is given by a PLC via Ethernet cable.
Yes, the VFD is housed in a MCC and individual VFD in it has its own brake resistor.

Yes, I do have access to the VFD screen, but better I trended the values and attached excel file.
Attached Files
File Type: zip Project12_Copy_1.zip (393.3 KB, 4 views)
File Type: xlsx BunkDrop2.xlsx (83.9 KB, 10 views)
File Type: xlsx BunkDrop3.xlsx (112.9 KB, 4 views)
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Old July 9th, 2019, 09:55 AM   #6
neilm
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I also reduced the original speed by 1/3rd and tried, yet the drive goes into those same faults.
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Old July 9th, 2019, 12:19 PM   #7
_Dock_
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Your DC bus volts are really high, you should take another pass at your braking resistor. The fact that the faults do not occur when the unit is unloaded is a sign that regen with the load may be causing your issue.

Ensure that the EXTERNAL braking resistor is wired and sized correctly for your application. If your using an internal braking resistor I have doubts that it is large enough to handle regen from an overhung load.

PowerFlex AC Drives: Expected DC bus voltage
530711 | Date Created: 02/28/2013 | Last Updated: 05/28/2018
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Question
What voltage can you expect on the DC bus?

Answer
Unloaded, DC bus voltage should be about line voltage times the square root of 2, loaded would be line times 1.3. With a soft line the DC bus could sag more.


Example calculation:

Unloaded 480Vac x 1.414 = 679Vdc

Loaded 480Vac x 1.30 = 624Vdc

Last edited by _Dock_; July 9th, 2019 at 12:22 PM. Reason: added
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Old July 9th, 2019, 12:24 PM   #8
_Dock_
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Nevermind, I didnt notice that this is a 600V drive.
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Old July 9th, 2019, 12:27 PM   #9
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AC Drives: F12 [Hardware Overcurrent] Faults Troubleshooting
107475 | Date Created: 09/18/2010 | Last Updated: 05/21/2019
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Question
What can cause a F12 [Hardware Overcurrent] fault in an PowerFlex AC drive and what can be done to troubleshoot or prevent this?

Environment
22A PowerFlex 4
22B PowerFlex 40
22C PowerFlex 400
22D PowerFlex 40P
22F PowerFlex 4M
25A PowerFlex 523
25B PowerFlex 525
20A PowerFlex 70
20B PowerFlex 700
20C PowerFlex 700H
20D PowerFlex 700S
20L PowerFlex 700L
20F PowerFlex 753
20G PowerFlex 755
Bulletin 160
Bulletin 1305
Bulletin 1333
Bulletin 1336
Bulletin 1336E
Bulletin 1336F
Bulletin 1336S
Bulletin 1336T
GV3000
VTAC7
SP500
SP600
VTAC9
LF2
Answer
A F12 [HW Overcurrent] fault indicates that the drive is sourcing current that is greater than 2-times its rating (generally around 250%). Therefore the motor is receiving this current as well.

Possible Causes and Solutions
One or more of the following items may cause an AC drive to produce a HW Overcurrent fault:

The motor nameplate information is not entered correctly in the drive parameters.
The motor is not wired correctly.
Moisture in the motor conduit box.
The motor nameplate current plus the cable charging current may exceed maximum drive output. Check the length of the motor leads from the drive to the motor. Specific information of cable length restrictions per drive family and power rating are in Appendix A of the Wiring and Grounding for Pulse Width Modulated (PWM) AC Drives Installation Instructions , Publication Drives-IN001. The third page into Appendix A you will see a table entitled "Motor Cable Length Restrictions Table Cross-reference". If you are not familiar with these tables, look for “How to Read the Motor Cable Length Restrictions Tables” also found in Appendix A.
The drive has not been tuned to the motor.
The run signal chatters. Check if the control mode is two-wire and repair the signal so that it is not intermittent.
The drive is starting the motor when the load is already spinning. To correct this turn on the flying start function in the drive.
A device such as a contactor or disconnect switch, wired between the drive and the motor, is changing state (opening/closing) after the drive is running. Make sure that all devices on output of the drive are closed and stay closed while the drive is running
The drive is running multiple motors but it is not in V/Hz mode.
The drive has an internal failure. To test for this, run it when the motor and motor leads are disconnected from the drive's output terminals and watch for a fault to occur. (Be sure to only test in this way while the drive is running in open loop mode. Turn off encoder feedback if it is enabled.)
An output reactor or output filter is connected between the drive and motor. Please refer to Parameter Settings for PowerFlex Drives Sine Wave and dv/dt Filters, and Adjustable Voltage Publication PFLEX-AT002. Ensure that the line reactor is sized appropriately based on the drive's respective technical data manual.
The drive may have one IGBT pair that is not providing an AC output when commanded. With the motor circuit disconnected, run the drive up to full motor speed and check the AC output voltage from phase to phase. When read with a volt meter (with low pass filter), the user should observe a balanced voltage condition. If the voltage is not balanced then one phase of IGBT pairs may not be providing an output. If one IGBT pair is not providing an AC output, if commanded, the motor/drive may attempt to run. However, both motor and drive would be operating in an extremely inefficient "single phasing" condition. In this state, the motor would fail to produce its rated torque / amp. So to meet a requested acceleration rate or load demand, it would demand significantly higher currents from the drive. While the drive would attempt to satisfy the requested current, it would only have two out of three transistor pairs with which to provide it. As a result the two remaining transistor pairs would be trying to pass considerably more current than normal. If a software trip did not shut down the drive, the IGBTs and heat sinks would heat up very quickly and hopefully trip a hardware thermostat and / or trip out on HW Overcurrent or IOC conditions.
There is a short in the motor windings. See the sections below regarding testing the health of the motor
Meggering the Motor
With the motor leads disconnected from the drive, megger the motor to see if its checks okay to ground. Acceptable voltage ranges and results are as follows:

400 volt Class motor, megger at 1500V, results = 100 MOhms or greater
600 volt Class motor, megger at 2000V, results = 100 MOhms or greater
Note: meggering a 1488 V rated motor at 1500 V will not fail the motor

If megger results are within the listed ranges then perform the following:

With the cables disconnected from the output of the drive, measure the resistance of each of the 3-phases connected to the motor. Make sure they are balanced and within reason considering the length of cable and the size of the motor.
Disconnect the drive and wire the motor so that it can be started directly across the 3-phase line. If it runs properly then measure the current on each phase. Verify that they are balanced.
Motor Surge Comparison Test
This is a test performed to determine winding insulation condition. This test detects turn-to-turn, coil-to-coil, and phase-to-phase insulation defects that cannot be discovered by other methods. A qualified motor shop will have this type of equipment.
Drive-Specific Troubleshooting and Solutions
PowerFlex 4M
If mechanical brake is used, a snubber may need to be added to dissipate the residual voltage.
PowerFlex 750
Set Parameter 43 [Flux Up Enable] and Parameter 44 [Flux Up Time] to a value of 0. This disables the flux regulator.
Set Parameter 70 [Autotune] to 0 and set Parameter 621 [Slip RPM at FLA] to 0. This disables the slip compensator in Volts/Hz (V/Hz) and Sensorless Vector (SVC) mode only.
If there is an encoder check encoder terminations for loose wires. Also, ensure that the encoder is not wired to the 24V supply as the A, B, and Z channels are rated 5-15 VDC.
To test encoder integrity, set the drive to open loop with Parameter 125 [Pri Vel Fdbk Sel].
Verify that motor nameplate data is correct in Parameter 25 [Motor NP Volts] through Parameter 31 [Motor Poles] (poles are usually entered incorrectly).
After tuning the drive to the motor (Parameter 70 [Autotune] should be set to 0 [Ready] if tune was completed), check that the value in Parameter 75[Flux Current Ref] is about 1/3 of the full load amps (FLA) of the motor. This should be true for motors that are above 25 HP.
If the drive is starting the motor when the load is already spinning then turn on the flying start function in Parameter 356 [FlyingStart Mode].
Disconnect the motor at the motor junction box and run the drive. Note how much current is drawn. Add this current to the nameplate amps (Parameter 26 [Motor NP FLA]). If drive still faults then drive may be damaged/undersized.
Detune the Speed Loop P636 [Speed Reg BW]
PowerFlex 700, SP600, VTAC9
Set Parameters 057 [Flux Up Mode] and Parameter 058 [Flux Up Time] to a value of 0. This disables the flux regulator.
If there is an encoder, configure the drive to open loop by setting Parameter 080 [Feedback Select] to a value of 0 [Open Loop].
Verify that motor nameplate data is correct in Parameter 040 [Motor Type] through Parameter 049 [Motor Poles] (poles are usually entered incorrectly).
After tuning the drive to the motor (Parameter 061 [Autotune] should be set to 0 [Ready] if the tune was completed), check that the value in Parameter 063 [Flux Current Ref] is about 1/3 of the full load amps (FLA) of the motor. This should be true for motors that are above 25 HP.
If the drive is starting the motor when the load is already spinning then turn on the flying start function in Parameter 169 [Flying Start En].
Disconnect the motor at the motor junction box and run the drive. Note how much current is drawn. Add this current to the nameplate amps Parameter 042 [Motor NP FLA]. If the drive still faults then the drive may be damaged/undersized.
Liquiflo 2
Compare inverter motor nameplate parameters Parameter 040 [Motor Type] to Parameter 048 [Motor OL Factor] with motor nameplate, if inverter Parameter 053 [Motor Cntl Sel] is set to sensorless vector verify that Parameter 062 [IR Voltage Drop] and Parameter 063 [Flex Current Ref] are set correctly for the motor.

If none of the above options work then replace the drive.
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Old July 9th, 2019, 01:32 PM   #10
neilm
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Thank you, Doc. I have done some of them, I'll try the rest.
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