3.2.6 Switching on the Output
Adding a switch to the output between the motor and the drive is allowed, however fault messages can appear.
3.2.7 Overload Protection
Power Limit
A power limit function limits the power distributed to the motor (power limit motor mode). Also, the power limit function can limit
generative power fed back into the mains supply (AFE) or fed to a brake resistor (power limit generator mode). The power limit function
is designed for flux open-loop control/closed-loop control and can be used for all motor types with flux control core (ASMPM).
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
l Minimum speed limit: parameter 4-12 Motor Speed Low Limit [Hz] limits the minimum operating speed range of the drive.
l Maximum speed limit: 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 the illustration
in 3.3.4 Motor Thermal Protection.
Overvoltage
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.
3.2.8 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+/flux control
(parameter 30-22 Locked Rotor Protection).
3.2.9 Automatic Derating
The drive constantly checks for the following critical levels:
l High temperature on the control card or heat sink.
l High motor load.
l High DC-link voltage.
l 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.
16 | Danfoss A/S © 2024.01 AJ435824192086en-000101 / 130R1295
Design Guide | VLT® AutomationDrive FC 360
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