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The drive withstands mains fluctuations such as:
Transients
Momentary dropouts
Short voltage drops
Surges
The drive automatically compensates for input voltages ±10% from the mains nominal to provide full rated output current. With
auto restart selected, the drive automatically powers up after a voltage trip. With flying start parameterization, the drive can syn-
chronize to a motor spinning freely after a mains dropout and bring it back to normal operation.
3.3.1.2 Missing Mains Phase Detection
The drive monitors the mains input and reacts according to the programmed configuration if improper conditions, such as missing
or detecting too high imbalance between the input phases.
Operation under severe mains imbalance conditions reduces the lifetime of the drive. Conditions are considered severe if the motor
is operated continously near nominal load. The default setting issues a warning, but automated derating of the load can also be
parameterized among multiple choices.
3.3.2 Output Protection
The VLT® Compressor Drive CDS 803 offers various built-in protection features for the compressor terminals U, V, and W.
3.3.2.1 Short-circuit Protection (Phase-to-phase)
The drive is protected against short circuits on the output side by current measurements. A short circuit between 2 output phases
causes an overcurrent internally and turns off all outputs once the short-circuit current exceeds the maximum limit. A drive that
works correctly limits the current it can draw from the supply. Still, it is recommended to use fuses and/or circuit breakers on the
supply side as protection if there is a component breakdown inside the drive (1
st
fault). Mains side fuses are mandatory for UL com-
pliance.
N O T I C E
To ensure compliance with IEC 60364 for CE or NEC 2017 for UL, it is mandatory to use fuses and/or circuit breakers.
3.3.2.2 Ground Fault Protection (Output Phase-to-Ground)
The drive is protected against ground faults on all output terminals, U, V, and W.
3.3.2.3 Locked Rotor Detection
Sometimes the rotor is locked because of excessive load or other factors preventing the compressor from rotating.
The drive detects the locked rotor situation and trips accordingly to prevent overheating the compressor and the drive.
N O T I C E
In regulation with UL 60730-1 certified products, the locked rotor detection cannot be disabled.
3.3.2.4 Output Phase Loss Detection
The drive monitors all outputs to detect any missing or interrupted connections. If no currents are drawn on any output, it is as-
sumed that no motor is connected and will cause this event to be triggered. If a single phase is lost, an output phase missing event
is triggered. In both scenarios all outputs are turned off. The missing output phase function is enabled by default to avoid motor
damage. Disabling this protection is possible via parameterization.
N O T I C E
In regulation with UL 60730-1 certified products, the output phase loss detection cannot be disabled.
3.3.2.5 Overload Protection
If excessive current outputs or high temperatures are observed for an unwanted period, the protections trip the drive and turn all
the outputs off. The time before the drive trips is controlled by parameterization of the monitored protections.
Voltage limit
The inverter turns off to self-protect the internal components when the maximum voltage limits are reached.
AJ330233902305en-000201 / 130R0596
20 | Danfoss A/S © 2021.05
Product Overview
VLT® Compressor Drive CDS 803
Design Guide
