NWL PowerPlus 7.5 Series User manual

PowerPlus Series 7.5
Troubleshooting Guide
For Customer Use

Table of Contents
Page
Introduction......................................................................................................................... 1
Understanding PowerPlus Alarms ...................................................................................... 1
PowerPlus Procedures......................................................................................................... 9
Open Circuit Test............................................................................................................ 9
Short Circuit Test.......................................................................................................... 11
Power Electronics Testing ............................................................................................ 12
Replacing the IGBT’s ................................................................................................... 14
Verification of the Gate Signals to the IGBT's for the Series 7.5 PowerPlus Units..... 20
Setup Instructions using a separate (external) 120 VAC power source.................... 20
Setup Instructions using the existing incoming 3 phase power source..................... 20
Verifying the gate pulses on the DSP Control Module............................................. 21
Verifying the gate pulse signals to the IGBT's for the 28 – 70 kW units. ................ 22
Verifying the gate pulse signals to the IGBT's for the 84 - 120 kW units................ 26
Verification of the Gate Signals to the IGBT's for the 128 - 200 KW PowerPlus ... 30

Page 1
Introduction
The purpose of this guide is to assist the user in the troubleshooting and repair of the
PowerPlus Series 7.5 and newer units. It is geared toward the power supply only and not
the precipitator portion of the collection process. The guide is divided into two sections.
The first section deals with analyzing the cause of the problem, while the second section
deals with specific procedures for testing and replacement of various components.
Only qualified trained personnel, with a complete understanding of the PowerPlus theory
of operation and circuit topology should be attempting repair of the PowerPlus units.
Lethal voltages exist within the unit.
Understanding PowerPlus Alarms
The troubleshooting process is usually called into play once a PowerPlus has recognized
an alarm condition exists and has tripped off. An understanding of the alarm messages
that are shown on the GVC display can be very helpful in the first step towards finding
the problem. Below is a list of the alarm messages that can appear, along with their
possible cause and solution.
•Undervoltage:Occurs when the kVDC is at or below a set value for a user-
determined period of time, indicating a short circuit or high spark rates in the
precipitator. The undervoltage trip level is adjustable.
Cause: Short circuit or close clearances in the precipitator causing it to spark at
low kV levels.
Solution: Perform an open circuit test to verify if problem is in ESP. Correct
problem in the field.
Cause: Incorrect settings for undervoltage, spark rate, setback, fast recovery, and
spark level.
Solution: Change settings to correct values as described in the section on
Changing Operating Parameters.
Cause: Readout not calibrated properly.
Solution: Recalibrate following instructions in the Calibration section.
•Overvoltage:Activated instantly if the kVDC exceeds its rating by 15%. This is a
fixed setpoint. This usually indicates an open circuit condition.
Cause: HV connection from the PowerPlus to the ESP section is not tight or
secure.
Solution: Perform a short circuit test to verify that the PowerPlus can produce
rated mADC. If it does, the open is in the connection to the ESP. Find
the loose or open connection and tighten it.

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Cause: Incorrect PowerPlus rating entered for unit.
Solution: Change rating to correct value.
Cause: Readout not calibrated properly.
Solution: Recalibrate following instructions in the Calibration section
•Line Overcurrent: Activated if the line current exceeds its rating by 15%. This is
a fixed setpoint. This alarm can be caused by excessive precipitator current, faulty
primary component (ie, three phase rectifier bridge, DC bus capacitor, etc.),
incorrect calibration, or a problem with the PowerPlus control board.
Cause: Excessive precipitator current
Solution: Make sure the current limit is properly set so the rating is not exceeded.
Cause: Faulty primary component
Solution: Identify which component is causing the excessive current and replace.
Component may not be shorted since the fuses did not fail, but there
may be excessive leakage current present.
Cause: Incorrect PowerPlus rating entered for unit.
Solution: Change rating to correct value.
Cause: Readout not calibrated properly.
Solution: Recalibrate following instructions in the Calibration section
•Output Overcurrent: Activated if the mADC exceeds its rating by 25%. This is a
fixed setpoint. It can be caused by either the failure to sense a spark/arc, or
incorrect calibration.
Cause: Failure to sense a spark/arc.
Solution: Make sure the spark/arc sensitivities are properly set. Adjust as
necessary, using an oscilloscope on the feedback waveforms as
verification.
Cause: Incorrect PowerPlus rating entered for unit.
Solution: Change rating to correct value.
Cause: Readout not calibrated properly.
Solution: Recalibrate following instructions in the Calibration section
•Overtemperature: The PowerPlus monitors both the IGBT heatsink temperatures
and the HV tank oil temperature. If either of these temperatures reaches a fixed
limit setpoint, the controller will reduced the Duty Cycle in an attempt to reduce
the temperature of the affected device. The display will show the message
Temperature Limit as it attempts to regulate the temperature. If the temperature
continues to rise and the fixed alarm setpoint is reached the unit will trip on
Overtemperature. The setpoint levels are listed below.

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Description IGBT Heatsink HV Tank
Temperature Limit Activation 93C 85C
Temperature Limit Release 90C 80C
Temperature Trip 95C 87C
You should first determine which component is causing the alarm by reading the
temperature values on the display.
Cause: Increase in ambient temperature
Solution: If the outside ambient is exceeding the rating, some means must be
taken to lower the ambient temperature.
Cause: Problem with the IGBT fan
Solution: Verify that the IGBT fan is rotating and the air is flowing toward the
heatsink. Also refer to the Fan Current Out of Range alarm below.
Cause: Problem with the heat exchanger (if applicable)
Solution: Verify that the enclosure heat exchanger (if applicable) is operating
(both fans are rotating) and the exchanger is clean of dirt and dust.
Cause: Problem with the HV tank
Solution: Verify that the any radiator fans (if included) are rotating and the air is
flowing. Verify the oil circulator internal to the tank is operational.
Verify that system is properly calibrated and ratings are not being
exceeded.
•Enclosure Over Temp: activates if the control enclosure temperature exceeds
65C (150F). This is a display only alarm and will not trip the unit. The Max.
Duty Cycle will be limited to 80% and the Temperature Limit icon will appear.
Cause: Increase in ambient temperature
Solution: If the outside ambient is exceeding the rating, some means must be
taken to lower the ambient temperature.
Cause: Problem with the heat exchanger (if applicable)
Solution: Verify that the enclosure heat exchanger (if applicable) is operating
(both fans are rotating) and the exchanger is clean of dirt and dust.
Cause: Problem with internal cooling fans
Solution: Verify that the internal enclosure fans are operating.
•HV Tank Fault: Activated whenever maximum duty cycle is reached but low
output KV and mADC, and high resonant current exists. This is indicative of a
fault within the T/R tank section of the PowerPlus.
Cause: A short circuit in the PowerPlus HV tank.
Solution: Call NWL service.

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•Liquid Level Low:Activated if the dielectric fluid level in the HV tank is low. It
is activated by the liquid level switch within the HV tank.
Cause: Possible tank leak
Solution: Inspect the tank for leaks and call NWL service.
Cause: Open in alarm sensing circuit
Solution: Verify that 120 VAC is present at the input to the alarm circuit. If it is
not, find the open in the circuit.
•Line VAC Abnormal: Activated if the incoming line voltage is outside of an
acceptable pre-defined range. That voltage range is dependent upon the rated line
voltage of the unit and is as follows:
Rated Line Voltage Acceptable Range
380 VAC 285 – 440 VAC
400 VAC 300 – 460 VAC
415 VAC 360 – 520 VAC
480 VAC 360 – 520 VAC
(400-480) VAC 360 – 520 VAC
If the line voltage returns to within the allowable range within 10 seconds, the
PowerPlus will automatically re-energize the high voltage. If it again experiences
the voltage out of range condition during ramp up, or if a second alarm occurs
within 5 minutes, the unit will trip and stay off until the alarm is manually
cleared.
Cause: Incoming line voltage outside of the specified range.
Solution: Change the tap at the power distribution transformer to bring the line
voltage within specification.
Cause: Loss of one of the incoming three phase lines.
Solution: Correct the phase loss problem.
•Low DC Bus Voltage: Activated if the DC bus voltage is less than 120% of the
line voltage. Since the low V Bus may have been caused by a low or unbalanced
three phase line voltage, the PowerPlus will continue to monitor the line voltage
for an additional 10 seconds after it trips. If the line voltage returns to within the
acceptable range listed above, the unit will automatically re-energize the high
voltage. If it again experiences the V Bus Low condition during ramp up, or if a
second alarm occurs within 5 minutes, the unit will trip and stay off until the
alarm is manually cleared.
Cause: Failure of main fuse(s) on the input to the 3Ø bridge rectifier.
Solution: Test for shorted 3Ø bridge rectifier, IGBT, or bus capacitor assembly.
Replace failed component then replace the fuse(s).

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Cause: Problem with contacts on main contactor or circuit breaker.
Solution: Verify all three phases are on the load terminals of the contactor and
breaker. Replace contactor/breaker if required.
Cause: Phase imbalance or loss of one of the incoming three phase lines.
Solution: Correct the phase imbalance/loss problem.
•Fan Current Fault: Activated if the IGBT heatsink fan current is less than .5 amp
or greater than 1.5 amp for 480 VAC fans and less than 1 amp or greater than 4
amp for 120 VAC fans (used on 21 kW and smaller units). If the tank fan
experiences a current fault, the alarm will be annunciated, but the unit will not
trip. The control will monitor the fluid temperature and go into a Temperature
Limit or Overtemp trip condition.
Cause: Problem with contacts on fan contactor
Solution: Verify all three phases are on the load terminals of the fan contactor.
Replace contactor if required.
Cause: Open or short circuit of the fan motor winding.
Solution: The winding of the fan motor are thermally protected with an internal
temperature cutout. If the motor is hot, allow it to cool and see if it can
be re-energized. If not replace motor. If it can be re-energized,
determine cause of overheating.
•Main Contactor Fault: Activated if the main contactor fails to energize based on
the status of the auxiliary contact. Since this alarm may have been caused by a
low incoming line voltage, the PowerPlus will continue to monitor the line
voltage for an additional 10 seconds after it trips. If the line voltage returns to
within the acceptable range listed above, the unit will automatically re-energize
the high voltage. If it again experiences the V Bus Low condition during ramp
up, or if a second alarm occurs within 5 minutes, the unit will trip and stay off
until the alarm is manually cleared.
Cause: Main contactor not energizing.
Solution: Check for 120 VAC at contactor coil. Check the small cylindrical fuse,
F2, located on the D25166-01 I/O board of the control module. Verify
that 120 VAC is present at the Aux. Main input on the control board.
Repair any faulty connections or replace contactor or control board if
required.
•Step Start Contactor Fault: Activated if the step start contactor fails to energize
(based on the status of the auxiliary contact).
Cause: Step start contactor not energizing.
Solution: Check for 120 VAC at contactor coil. Check the small cylindrical fuse,
F1, located on the D25166-01 I/O board of the control module. Verify

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that 120 VAC is present at the Aux. Step input on the control board.
Repair any faulty connections or replace contactor or control board if
required.
•Fan Contactor Fault: Activated if the fan contactor fails to energize based on
the status of the auxiliary contact. Since this alarm may have been caused by a
low incoming line voltage, the PowerPlus will continue to monitor the line
voltage for an additional 10 seconds after it trips. If the line voltage returns to
within the acceptable range listed above, the unit will automatically re-energize
the high voltage. If it again experiences the V Bus Low condition during ramp
up, or if a second alarm occurs within 5 minutes, the unit will trip and stay off
until the alarm is manually cleared.
Cause: Fan contactor not energizing.
Solution: Check for 120 VAC at contactor coil. Check the small cylindrical fuse,
F3, located on the D25166-01 I/O board of the control module. Verify
that 120 VAC is present at the Aux. Fan input on the control board.
Repair any faulty connections or replace contactor or control board if
required.
•Gate High Temp: Activates if the gate driver chip on the dual gate driver board
exceeds 70
o
C. This trip is wired into the Auxiliary Alarm #1 circuit and is only
on the Series 05 and later PowerPlus units. This alarm is not applicable to the
Series 7.5 units. It is only used on Series 5 through Series 7 models.
Cause: Gate driver board fan is not energizing.
Solution: Check for broken wiring from fan to board. Replace driver board if
required.
Cause: Open or intermittent wiring to thermal switch.
Solution: Check the 120 VAC wiring to J2 on the driver boards and on to J9-5 on
the I/O board.
Cause: Increase in ambient temperature
Solution: Verify that the enclosure heat exchanger (if applicable) is operating and
clean of dirt and dust. If the outside ambient is exceeding the rating,
some means must be taken to either lower the temperature or de-rate
(reduce the load on) the PowerPlus.
•Door Open: Activates if any of the non-mechanically interlocked doors on the
PowerPlus are open.
Cause: Door left open
Solution: Locate the open door and close it.
Cause: The door switch mechanism is not fully engaged.
Solution: Make sure the switch plunger is fully engaged upon door closing.

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Cause: Open or intermittent wiring to door switch.
Solution: Verify that 120 VAC is present on the Door Limit Switch input of the
control board. Repair any faulty connections.
•Low Battery: Signals that the battery in the controller’s non-volatile RAM has
dropped below an acceptable value.
Cause: Problem with RAM chip
Solution: Replace battery on RAM chip, then recalibrate following instructions in
the Operators Manual.
•Loss of Memory: Shows that the parameters stored in RAM have been wiped out.
Cause: Line surge or other electrical anomaly scrambles memory.
Solution: Verify unit is properly grounded. Verify the quality of the incoming
power.
Cause: Failure of nonvolatile RAM.
Solution: Replace RAM battery; then recalibrate following instructions in the
Calibration section
•Auxiliary Alarm:Activated instantly if any of the customer supplied auxiliary alarm
circuit are activated.
Cause: One of the customer supplied auxiliary alarm circuits was activated.
Solution: Check the specific auxiliary alarm circuit and correct the condition.
Cause: Incorrect input to alarm circuit.
Solution: Check the wiring to the auxiliary input and verify that the proper signal
is being applied to the input. Correct if necessary.
•Hammer Feedback Alarm:Activated instantly if any of the customer supplied
rotating hammer feedback alarms are activated. This alarm is only applicable if the
PowerPlus includes the option rotating hammer control board.
Cause: One of the rotating hammer motor starters is not energizing.
Solution: Check the specific rotating hammer motor starter and correct the
condition.
Cause: Incorrect input to alarm circuit.
Solution: Check the wiring to the hammer feedback alarm input and verify that
the proper signal is being applied to the input. Correct if necessary.

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A comparison of existing metering values for a given PowerPlus unit to a historical trend
of metering values may also be helpful in troubleshooting problems. Below is a chart
that summarizes the effect of the fault conditions on the metering values of the PowerPlus.
Troubleshooting Table
Condition Vac Iac Vbus Iresonant kVdc mAdc SPM Duty Cycle
High Input Line H LDC H HDC N HDC N N
Low Input Line L HDC L LDC N LDC N N
1 Blown Fuse N HDC
or 0
L LDC LDC LDC LDC N
2 or 3 Blown Fuses N L or 0 0 0 0 0 0 100%
IGBTs not firing (>=2) N L or 0 N 0 0 0 0 100%
1 IGBT not firing N LDC N LDC LDC LDC LDC N
HV tank short N L N H L L 0 100%
ESP short or reduced
clearance
N L N L L L to N 0 to N L to N
Codes:
N- Normal
L- Lower than Normal
H- Higher than Normal
LDC- Lower than typical for a given Duty Cycle
HDC- Higher than typical for a given Duty Cycle