Danfoss VLT AutomationDrive FC 361 Series Design Manual page 11

Product Overview and Featur...
3.2.6 Overload Protection
Torque limit
The torque limit feature protects the motor against
overload, independent of the speed. Torque limit is
controlled in parameter 4-16 Torque Limit Motor Mode and
parameter 4-17 Torque Limit Generator Mode. The time
before the torque limit warning trips is controlled in
parameter 14-25 Trip Delay at Torque Limit.
Current limit
The current limit is controlled in parameter 4-18 Current
Limit, and the time before the drive trips is controlled in
parameter 14-24 Trip Delay at Current Limit.
Speed limit
Minimum speed limit: Parameter 4-11 Motor Speed Low
Limit [RPM] or parameter 4-12 Motor Speed Low Limit [Hz]
limit the minimum operating speed range of the drive.
Maximum speed limit: Parameter 4-13 Motor Speed High
Limit [RPM] or parameter 4-19 Max Output Frequency limits
the maximum output speed that the drive can provide.
Electronic thermal relay (ETR)
ETR is an electronic feature that simulates a bimetal relay
based on internal measurements. The characteristic is
shown in Illustration 3.1.
Voltage limit
The inverter turns off to protect the transistors and the DC
link capacitors when a certain hard-coded voltage level is
reached.
Overtemperature
The drive has built-in temperature sensors and reacts
immediately to critical values via hard-coded limits.
3.2.7 Locked Rotor Protection
There can be situations when the rotor is locked due to
excessive load or other factors. The locked rotor cannot
produce enough cooling, which in turn can overheat the
motor winding. The drive is able to detect the locked rotor
+
situation with PM VVC control (parameter 30-22 Locked
Rotor Protection).
3.2.8 Automatic Derating
The drive constantly checks for the following critical levels:
•
High temperature on the control card or heat
sink.
•
High motor load.
•
High DC-link voltage.
•
Low motor speed.
As a response to a critical level, the drive adjusts the
switching frequency. For high internal temperatures and
low motor speed, the drive can also force the PWM pattern
to SFAVM.
MG06K102
Design Guide
NOTICE
The automatic derating is different when
parameter 14-55 Output Filter is set to [2] Sine-Wave Filter
Fixed.
3.2.9 Automatic Energy Optimization
Automatic energy optimization (AEO) directs the drive to
monitor the load on the motor continuously and adjust
the output voltage to maximize efficiency. Under light
load, the voltage is reduced and the motor current is
minimized. The motor benefits from:
•
•
•
There is no need to select a V/Hz curve because the drive
automatically adjusts motor voltage.
3.2.10 Automatic Switching Frequency
The drive generates short electrical pulses to form an AC
wave pattern. The switching frequency is the rate of these
pulses. A low switching frequency (slow pulsing rate)
causes audible noise in the motor, making a higher
switching frequency preferable. A high switching
frequency, however, generates heat in the drive that can
limit the amount of current available to the motor.
Automatic switching frequency modulation regulates these
conditions automatically to provide the highest switching
frequency without overheating the drive. By providing a
regulated high switching frequency, it quiets motor
operating noise at slow speeds, when audible noise control
is critical, and produces full output power to the motor
when required.
3.2.11 Automatic Derating for High
The drive is designed for continuous, full-load operation at
switching frequencies between 1.5–2 kHz for 380–480 V.
The frequency range depends on power size and voltage
rating. A switching frequency exceeding the maximum
allowed range generates increased heat in the drive and
requires the output current to be derated.
An automatic feature of the drive is load-dependent
switching frequency control. This feature allows the motor
to benefit from as high a switching frequency as the load
allows.
Danfoss A/S © 03/2019 All rights reserved.
Increased efficiency.
Reduced heating.
Quieter operation.
Modulation
Switching Frequency
3 3
9