Danfoss VLT 3032, VLT 3052, VLT 3042 Service Manual

Table of Contents

Page

Introduction 2
Safety 2

Section One

Section Two

Section Three Static
Test Procedures

Section Three Dynamic
Test Procedures

Section Four

Description of Operation 5
Sequence of Operation 9

Status Messages 11
Warning Messages 12
Alarm Messages 13
Troubleshooting T ips 17
Flow Charts 18
Symptom/Cause Charts 21

Testing the Soft Charge Circuit 23
Testing the Input Rectifiers 25
Testing the Inverter Section 26
Testing the Heatsink Temperature Sensor 27

Testing for Output Phase Imbalance 27
Testing Gate Drive Firing Circuits 28
Testing Input Rectifiers 30
Testing for Current Feedback 30

Removing and Replacing the Control Card 31
Removing and Replacing the Interface Board 31
Removing and Replacing Gate/Snubber/IGBT 32
Removing and Replacing Input Rectifiers 33

Section Five

Appendix

Current Limit Trips 35
Unstable Motor Operation 35
Ground Fault Trips 37
Overcurrent Trips 37
Overvoltage Trips 38
Overtemperature Trips 39

Additional Fault Codes I
Spare Parts List II
Block Diagram VLT 3032 III
Block Diagram VLT 3042 IV
Block Diagram VLT 3052 V

1

INTRODUCTION

The purpose of this manual is to provide technical information and
instructions that will enable the user to identify faults and affect repairs
on Danfoss series 3000 Adjustable Frequency Drives, VL T 3032 through
VLT 3052, 230 Volt models.

The manual has been divided into five sections. The first section covers
the description and sequence of operations. Section two covers fault
messages and provides troubleshooting charts both in the form of flow
and symptom/cause. Section three describes the various tests and
methods used to evaluate the drives' condition. Section four covers
the removal and replacement of the various components. Section five
discusses application-specific information.

ESD SAFETY

Electrostatic discharge. Many electronic components are sensitive to
static electricity . Voltages so low that they cannot be felt, seen or heard
can reduce the life, affect performance, or completely destroy sensitive
electronic components.

When performing service, proper ESD equipment should be used to
prevent possible damage from occurring.

2

SAFETY

WARNING:

FOR YOUR SAFETY:

The Adjustable Frequency Drive (AFD) contains dangerous voltages
when connected to the line voltage. Only a competent technician should
carry out the service.

1) DO NOT touch the electrical parts of the AFD when the AC line is
connected. After the AC line is disconnected wait at least 15 minutes
before touching any of the components.

2) When repairs or inspection is made the AC line must be
disconnected.

3) The STOP key on the control panel does not disconnect the AC
line.

4) During operation and programming of the parameters the motor
may start without warning. Activate the STOP key when changing
data.

3

4

SECTION ONE

DESCRIPTION OF
OPERATION

LOGIC SECTION

MICROPROCESSOR

RAM

CONTROL

DATA

ADRESS

EPROM

EEPROM

VVC

POWER

KEYBOARD
DISPLAY

Refer to the overall schematic in the Appendix.
It is not the intention of this manual to enter into a detailed description

of the unit's operation. Moreover, it is intended to provide the reader
with a general view of the unit's main assemblies. With this information,
the repair technician should have a better understanding of the unit's
operation and therefore aid in the troubleshooting process.

The VLT is divided primarily into three sections commonly referred to
as: logic, power, and interface.

The control card itself primarily makes up the logic section. The heart
of the control card is a microprocessor which controls and supervises
all functions of the unit's operation. In addition, a separate PROM
contains the parameter sets which characterize the unit and provide
the user with the definable data enabling the unit to be adjusted to
meet the customer's specific application. This definable data is then
stored in an EEPROM which provides security during power-down and
also allows flexibility for future changes as needed. A custom integrated
circuit generates the PWM waveform which is then sent on to the
interface board for distribution to the individual gate drive circuits.

Also, part of the logic section is the keyboard/display
mounted on the control card. The keyboard provides
the interface between the digital logic and the human
programmer. The LCD (Liquid Crystal Display)
provides the operator/programmer with menu
selection, unit status and fault diagnostic information.
Programming is accomplished through the use of four

D

A

POWER

FEEDBACK

2

1

ANALOG
INPUTS

DIGITAL
INPUTS

of the eight keys available on the keyboard. The
additional four keys provide Local Start, Stop, Forward/
Reverse and Jog.

A series of customer terminals are provided for the
input of remote commands such as: Run, Stop and
Speed Reference. Terminals are also provided to
supply outputs to peripheral devices for the purpose
of monitoring and control. Two programmable relay

D

ANALOG
OUTPUTS

A

1

outputs are also available to interface the unit with other
devices.

In addition, the control card is capable of

DIGITAL
CHANNEL

1

communicating via a serial link with outside devices
such as a personal computer or a programmable logic
controller.

RELAY

The control card provides two voltages for use from
the customer terminal strip. The 24VDC is used
primarily to control functions such as: Start, Stop and
Forward/Reverse. The 24VDC is provided from a
separate section of the unit's power supply and is
delivered to the control card from the interface board
via the two conductor ribbon cable.

5

LOGIC SECTION
(continued)

A 10VDC supply is also available for use as a speed reference when
connected to an appropriate potentiometer. These two voltage
references are limited in the amount of available current they can provide
(see specifications in Instruction Manual). Attempting to power devices
which draw currents in excess of that available may result in an eventual
failure of the power supply. In addition, if the supply is loaded too
heavily, sufficient voltage will not be available to activate the control
inputs.

During the troubleshooting process it is important to remember that the
control card can only carry out instructions as it has been commanded.
Of course, it is possible that as a result of a failure the control card may
fail to respond to commands. For this reason lies the necessity to
isolate the fault to the control commands, the control program or the
control card itself. If, for example, the unit does not run, but yet an
obvious reason is not apparent, check for proper control signals. Has
a run command been provided on the correct terminal; and if so, has
that terminal been designated as such in the programming of the control
card. In addition, be sure to verify that commands are being received
by testing for the presence of voltage on the appropriate terminals.
Never assume the signal is present because it is suppose to be. If
ever in doubt of whether the remote controls are functioning properly , it
is possible to take local control of the unit to verify if the control card is
operational. A word of caution here: prior to taking local control, insure
all other equipment associated with the drive is prepared to operate.
In many cases, safety interlocks are installed which can only be activated
through the use of a normal remote control start. In the same sense
that the control card can only respond to commands, comes the situation
that the control card makes a response without the presence of an
actual command. By the term response, it is not meant to infer that the
control card initiates such actions as Run or Stop, but rather suggests
that the control card displays unknown data or its performance is affected
as in what might be speed instability. In these cases, the first instinct
may be to replace the control card; however, in most instances, this
type of erroneous operation is usually due to electrical noise being
injected onto the remote control signal wiring. Although the control
card has been designed to reject such interference, noise levels of
sufficient amplitude can, in fact, affect the performance of the control
card.

As mentioned, sufficient levels of electrical noise can cause such things
as speed fluctuations as a result of interference with the speed reference
or with the operation of the microprocessor. In these situations it is
necessary to investigate the wiring practices of the installation. For
example, are the control signal wires running in parallel with other higher
voltage signals such as the input or output power wiring? As wires are
passed in close proximity to one another, voltages are induced through
capacitive or inductive coupling. This type of problem can be corrected
by rerouting the wiring or through the use of shielded cable. When
employing the use of shielded cable, it is important to properly terminate
the drain wire. The drain wire is terminated only at the control card end
of the wire. Specific terminals are designated for this purpose. The
opposite end of the shielded cable drain wire is then cut back and
taped off to prevent it from coming in contact with ground or acting as
an antenna.

6

LOGIC TO POWER
INTERFACE

The logic to power interface isolates the high voltage components of
the power section from the low voltage signals of the logic. This is
accomplished by use of the interface board. All communication between
the control logic and the rest of the unit passes through the interface
board. This communication includes: feedback from the current sensors,
input from the heatsink temperature sensor, line voltage monitoring,
DC Bus voltage monitoring, control of the fans , control of the input
thyristor rectifiers and control of the gate drive firing signals. Also on
the interface board is the power supply which provides the unit with
low voltage power such as 24VDC, 16VDC, 13VDC and 5VDC. The
power supply is a Switch Mode Power Supply (SMPS). The switch
mode type supply is used due to its efficiency and linearity. Another
benefit of the switch mode supply is that it obtains its power from the
DC Bus; in the event of a power loss the power supply remains active
for a longer period of time versus conventional power supplies.

During the troubleshooting process it is important to determine whether
the interface board is receiving or sending the signal that appears to
be at fault. For example, the loss of a gate-drive signal is a waveform
generated by the interface board and conversely a heatsink over­temperature fault is a result of the interface board receiving an input
from the heatsink temperature sensor . If the signal is of the later type
(received), it is then necessary to isolate the fault to either the sending
device or the interface board. It is generally assumed that a component
within the unit is usually at fault; and although this may in fact be the
case, it is critical to check all possibilities to avoid costly errors and
lengthy downtime. In any case, the interface board is a relatively quick
and easy assembly to exchange; and so if it is suspect, a quick exchange
will prove the assumption.

7

POWER SECTION

The power section is made up of the SCR/Diode modules (input
rectifiers), the soft charge circuit, the DC capacitor bank, the gate drive
and snubber cards and the IGBT power devices. Also located in the
power section are the DC Bus coil, the motor coils and, although not
typically considered part of the power section, the output phase current
sensors.

During the troubleshooting process, extreme care is required when
probing into the power section components. The DC Bus, when fully
charged, can be as high as 350VDC. Although this voltage begins to
decrease upon the removal of input power , it takes up to approximately
fifteen minutes to fully discharge the DC capacitor bank. Located on
the interface board is the Bus Charged Indicator. The red LED is visible
through the shield covering the lower portion of the interface board;
and as long as it is lit it indicates the DC Bus voltage is greater than
50VDC. A fault in the power section will usually result in at least one of
the incoming line fuses being blown. If one or more line fuses have
blown, it is not recommended to replace them and reapply power without
further investigation. In a case such as this, it would be suggested to
conduct the tests listed under Static Test Procedures in Section Three.
These tests will result in a thorough check of all the components
operating in the power section. In addition, following the identification
and replacement of power section components, it is recommended to
disconnect the motor wires prior to reapplying power . This precaution
opens the path for short circuit currents through the motor in the case
that all faulty components have not been replaced.

DC BUSRECTIFIER

R
S

T

SIMPLFIED PWM POWER SECTION

INVERTER

M

3Ø

8

SEQUENCE OF
OPERATION

When input power is first applied, the SCR/Diode modules (input
rectifiers) are not gated so the incoming line voltage is rectified by the
soft charge rectifier (BR1). As the DC Bus capacitors charge, the inrush
current is limited by the series soft charge resistors (R2 and R3).
Following a time delay of approximately one second, the interface board
monitors the DC Bus voltage and, providing it has reached an acceptable
level, begins sending gate pulses to the SCR/Diode Modules. Once
the SCR's have been gated on, they remain in this state and the SCR/
Diode modules act as a normal rectifier. This scenario will only be
interrupted if the DC Bus fails to charge. This can be caused by
insufficient line voltage, a fault in the Power Section, a fault in the soft
charge circuit, and also by an open connection at PINS 1 and 2 of
MK15. The SCR Disable input at MK15 is provided as a means to
disable the SCR/Diode modules in the case of an external failure such
as in the Dynamic Brake option. Note that although the SCR/Diode
modules may be disabled, line voltage is still applied to the unit through
the soft charge circuit.

Providing the charging process proceeds normally , the power supplies
will come up and provide the control card and all other sections of the
unit with low voltage control power. At this time the display in the
control card will indicate the unit is ready for operation.

Following a run command and a speed reference, the control card
delivers the PWM signals (one for each phase) to the interface board.
The interface board in turn receives these three signals and creates
the six individual gate drive pulses. The gate drive pulses are sent to
the respective gate drive circuits located on the gate drive card. From
here the output power devices (IGBTS) are switched on and off to
develop the PWM waveform which is ultimately delivered to the motor .

As the unit operates, the interface board monitors the status of the
units operating condition. Currents in excess of limits, temperatures
being exceeded, and voltages out of specification will result in the
interface board responding with a fault and sending the appropriate
fault message to the control card. When a fault occurs, the interface
board will indicate the condition via a series of LED's. The control card
will also display a fault message, and in virtually all cases trip the unit
off line. Section 2 of this manual describes the fault LED's and
messages and provides direction in determining the cause and the
solution for the fault condition.

9

SECTION TWO

FAULT INDICATORS
AND MESSAGES

A variety of messages are displayed by the control card. Some of
these indicate the operational status of the unit while others provide
warnings of an impending fault. In addition, there are the alarm
messages which indicate that the unit's operation has stopped due to
a fault condition. In this section we will deal with only those messages
which interrupt the unit's operation. A complete list of status messages
can be found in the Instruction Manual. Along with the control card
message, the interface board contains several Light Emitting Diodes
(LED's) which aid in the identification of the fault condition.

STATUS MESSAGES

CURRENT LIMIT

This message will flash in the display when the unit is operating above
the current limit setting as recorded in parameter 209. Parameter 310
may be set to provide a fixed time delay after which the unit will trip.

REF FAULT

This message will flash in the display should any live zero signal be
operating outside of its range. For example, 4-20ma has been selected
as the speed reference. Should the current loop be broken, the display
will flash "REF FAULT". Parameters 414 and 415 may be used to
select the unit's response to this condition.

NO 24 VOLT

This message will flash if the 24 volt power supply is missing or out of
tolerance. The 24 volt supply is used only for the customer's remote
connections.

NO MOTOR

This message will flash if Motor Check has been activated in parameter
313, terminal 27 is enabled and no motor is detected.

11

WARNING MESSAGES

VOLTAGE LOW

This message will flash when the DC Bus voltage has fallen below the
lower limit. This is an indication of low line voltage. This is only a
warning message, however. If the condition persists, it will result in a
unit trip on "Under Voltage".

VOLTAGE HIGH

This message will flash when the DC Bus voltage has exceeded the
upper limit. This is an indication of high line voltage or regenerative
energy being returned to the bus. This is only a warning message,
however. If the condition persists, it will result in a unit trip on "Over
Voltage".

INVERT TIME

This message will flash when the inverter ETR value has reached 98%.
The inverter ETR begins counting up as soon as the output current
exceeds 105% of the unit's continuous current rating. At an inverter
ETR value of 100%, the unit trips on "Invert Time".

MOTOR TIME

This message will flash if Motor Thermal Protection has been activated
in parameter 315 and the motor ETR value has reached 98%. The
motor ETR value begins counting up if the motor is run at slow speed
or if the motor is consuming more than 116% of the motor's nominal
rated current as entered in parameter 107. At a motor ETR value of
100%, the unit will respond based on the setting in parameter 315. If
Trip has been selected, the unit will trip on "Motor Time".

OVERCURRENT

This message indicates at least one of the three output phases has
reached the peak current rating. In addition, the "Overcurrent" LED
(D8) on the interface board will flicker. During this time the control card
is attempting to initiate current limit. If the current rises to fast or the
control card cannot control the condition by means of current limit, the
unit will trip on "Over Current".

12

ALARM MESSAGES

Alarm messages will be indicated by the following messages appearing
in the display and the red alarm LED being lit on the control panel. All
alarm messages result in the unit's operation being interrupted and
require a Manual or Automatic reset. Automatic reset can be selected
in parameters 309 and 312. In addition, the message "Trip" or "Trip
Locked" will be displayed. If "Trip Locked" is displayed, the only possible
reset is to cycle power and then perform a manual reset. Manual reset
is accomplished by means of the front panel push button or by a remote
contact closure on the appropriate control terminal. Remedies listed
with each alarm message give a basic description of the corrective
action which can be taken to correct the fault condition. For a more
detailed explanation, see the Sympton/Cause section beginning on page
21 and the application section on page 35. Also note the numbers in
parenthesis by each alarm message. These are the codes which will
appear in the Fault memory , Parameter 602. See APPENDIX I for more
on the Fault memory.

INVERTER FAULT (1)

This message indicates a fault in the power section of the unit. This
message may also be displayed if the unit has detected a phase loss
on the input. If a phase loss has been detected, the "Loss of Phase"
LED (D9) on the interface board will be illuminated and the "Inverter
OK" LED (D4) on the interface board will be out. This fault returns a
"Trip Locked". Also see Testing The Inverter Section, page 26.

OVER VOLTAGE (2)

This message indicates the DC Bus voltage upper limit has been
exceeded. In addition, the "High Bus Voltage" LED (D5) on the interface
board will be illuminated and the "Inverter OK" LED (D4) on the interface
board will be out. This fault can be caused by high line voltage or
regenerative energy being returned from the motor. To remedy this
fault condition, reduce the line voltage or extend the Decel Ramp. This
fault returns a "Trip". Also see Over Voltage Trips, page 38.

UNDER VOLTAGE (3)

This message indicates the DC bus voltage has fallen below the lower
limit. In addition, the "Low Bus Voltage" LED (D6) on the interface
board will be illuminated and the "Inverter OK" LED (D4) on the interface
board will be out. To remedy this fault, increase the line voltage to the
correct value for the unit rating. This fault returns a "Trip". Also see
Testing The Soft Charge Circuit, page 23.

OVER CURRENT (4)

This message indicates a short circuit on the output of the inverter.
This fault may also be caused by the unit reaching the peak current
rating too rapidly for the unit to respond with current limit. An example
may be closing an output contactor with the unit at speed and a high
inertia load. The "Overcurrent Trip" LED (D7) on the interface board
will be illuminated and the "Inverter OK" LED (D4) on the interface
board will be out. To remedy this fault, check the output wiring and
motor for short circuits. This fault returns a "Trip Locked". Also see
Over Current Trips, page 37.

13

ALARM MESSAGES
(continued)

GROUND FAULT (5)

This message indicates a leakage to ground on the output of the inverter.
The "Ground Fault Trip" LED (D2) on the interface board will be
illuminated and the "Inverter OK" LED on the interface board will be
out. This fault will also be present if the programming card on the
interface board is not installed. To remedy this fault, check the output
wiring and motor for ground faults. This fault returns a "Trip Locked".
Also see Ground Fault Trips, page 37.

OVER TEMP (6)

This message indicates that the unit's heatsink temperature or the unit's
internal ambient temperature has exceeded permissible limits. This
fault may also be caused by a trip received from the optional external
temperature sensor if a sensor has been connected to terminal MK15
on the interface board. The interface board LED's indicate the nature
of the specific trip. In all cases below the "Inverter OK" LED will be out.
"Over Temperature Trip" LED (D3) only indicates the unit's heatsink
sensor has caused the trip. "Over Temperature Trip" LED (D3) and
Internal Over T emperature" LED (D109) illuminated indicates the thermal
sensor located on the interface board has detected high ambient
temperature within the unit and caused the trip. "Over Temperature
Trip" LED (D3) and "External Over Temperature" LED (D108) illuminated
indicates the external temperature sensor has caused the trip. To
remedy this fault, correct the over-temperature condition. This fault
returns a "Trip". Also see Overtemp Trips, page 39.

INVERT TIME (7)

This message indicates the unit has delivered greater than 105% of
the unit's continuous current rating for too long (inverse time function).
Prior to this fault condition the "Invert Time" warning will be displayed.
An indication from the interface board status LED's does not apply . To
remedy this fault, reduce the motor load to at or below the unit's
continuous current rating. This fault returns a "Trip Locked". During
the trip the counter will count down. Upon reaching 90%, the "Trip
Locked" will change to "Trip".

MOTOR TIME (8)

This message indicates the motor has consumed greater than 1 16% of
the motor's nominal current rating for too long as entered in parameter

107. This fault may also be caused from running the motor at a low
speed and high current for too long a period of time. This trip will only
occur if the "Motor Thermal Protection" has been activated in parameter

315. Prior to the trip the "Motor Time" warning will be displayed. In
addition, this fault may be displayed if an external thermistor has been
connected to input 16 and is defective, disconnected or indicating an
over-temperature condition. Also note that by selecting "Thermistor" in
parameter 400 in error will result in a "Motor Time" fault. An indication
from the interface board status LED's does not apply. To remedy this
fault, reduce the load on the motor or raise the motor's speed. This
fault returns a "Trip Locked". During the trip the counter will count
down. Upon reaching 0% the "Trip Locked" will change to "Trip".

14