Drive And Motor Applications; Torque Limit, Current Limit, And Unstable Motor Operation - Danfoss VLT FC Series Service Manual

Drive and Motor Application...

7 Drive and Motor Applications

7.1 Torque Limit, Current Limit, and
Unstable Motor Operation
Excessive loading of the drive can result in warning or
tripping on torque limit, overcurrent, or inverter time. This
situation is not a concern if the drive is properly sized for
the application and intermittent load conditions cause an
occasional trip. However, nuisance or unexplained
occurrences can be the result of improperly set parameters.
The following parameters are important in matching the
drive to the motor for optimum operation.
•
Parameter 1-00 Configuration Mode sets the drive
for open or closed-loop operation, or torque
7 7
mode operation.
•
Parameter 1-03 Torque Characteristics sets the
mode in which the drive operates.
•
Parameters 1-20 to 1-29 match the drive to the
motor and adapt to the motor characteristics.
•
Parameter 4-16 Torque Limit Motor Mode,
parameter 4-17 Torque Limit Generator Mode, and
parameter 14-25 Trip Delay at Torque Limit set the
torque control features of the drive for the
application.
Parameter 1-00 Configuration Mode
This parameter sets the drive for open loop, closed loop, or
torque mode operation. In a closed-loop configuration, a
feedback signal controls the drive speed. The settings for
the PID controller play a key role for stable operation in
closed loop, as described in the operating instructions. In
open loop, the drive calculates the torque requirement
based on current measurements of the motor.
Parameter 1-03 Torque Characteristics
This parameter sets the drive for constant or variable
torque operation. It is imperative that the correct torque
characteristic is selected. For example, if the load type is
constant torque, such as a conveyor, and [1] Variable torque
is selected, the drive can have difficulty starting the load.
Consult Danfoss if uncertain about the torque character-
istics of an application.
Parameter 1-20 Motor Power [kW] and
parameter 1-25 Motor Nominal Speed
These parameters configure the drive for the connected
motor. These parameters are motor power, voltage,
frequency, current, and nominal motor speed. Accurate
setting of these parameters is important. Enter the
required motor data as listed on the motor nameplate. For
proper load control, the drive relies on this information for
calculating the output waveform in response to the
application demands.
80
®
VLT FC Series, D1h–D8h, Da2/Db2/Da4/Db4, E1h–E4h, J8/J9
Parameter 1-29 Automatic Motor Adaptation (AMA)
This parameter activates the automatic motor adaptation
(AMA) function. When AMA is performed, the drive
measures the electrical resistance of the motor stator
windings (R1). Parameter 1-31 Rotor Resistance (Rr) –
parameter 1-35 Main Reactance (Xh) must be requested
from the motor manufacturer the optimal performance of
the drive data. To set parameter 1-31 Rotor Resistance (Rr) –
parameter 1-35 Main Reactance (Xh), use the values
supplied by the motor manufacturer or leave at the factory
default values.
Never adjust these parameters to random values even
though it seems to improve operation. Such adjustments
can result in unpredictable operation under changing
conditions.
Parameter 4-17 Torque Limit Generator Mode and
parameter 4-16 Torque Limit Motor Mode
These parameters set the limit for the drive torque. The
factory setting is 160% for VLT
and 110% for VLT
202 and varies with motor power setting. For example, a
drive programmed to operate a smaller motor yields a
higher torque limit value than when programmed for a
larger motor. It is important that this value is not set too
low for the requirements of the application. Sometimes, it
can be desirable to have a torque limit set at a lower
value. This offers protection for the application as the drive
limits the torque. It can, however, require higher torque at
initial start-up, which can cause nuisance tripping.
Parameter 14-25 Trip Delay at Torque Limit
This parameter works with torque limit. This parameter
selects the period in which the drive operates in torque
limit before a trip. The factory default value is Off. This
setting means that the drive does not trip on torque limit,
although the unit can still trip from an overload condition.
Built into the drive is an internal inverter thermal
protection circuit. This circuit monitors the output load on
the inverter. If the load exceeds 100% of the continuous
rating of the drive, a timer is activated. If the load remains
excessive long enough, the drive trips on inverter time.
Adjustments cannot be made to alter this circuit. Improper
parameter settings effecting load current can result in
premature trips of this type. The timer can be shown on
the LCP.
Danfoss A/S © 02/2019 All rights reserved.
®
AutomationDrive FC 302
® ®
HVAC Drive FC 102/VLT AQUA Drive FC
MG94A502