On the display
The panel shows FLTR LOW BUS VOLTAGE FLT. The manual prints the message only in this single form, so the text on the display matches it exactly.
What it means
The harmonic filter creates the filter DC link voltage itself, doing so by switching its IGBT's. The DC level it produces sits above what simple rectification of the input line would deliver, so the filter works as a voltage “boost” stage. That boost is what allows current to be pushed from the filter into the power line while the input line sits at its peak. This shutdown, and the message shown with it, is generated when the voltage on the filter's DC link falls to a point less than 60 VDC below the setpoint.
Why it appears
- When this shutdown happens only occasionally, the manual names a severe sag of the input line voltage as the likely cause.
- The setpoint the trip compares against is not a fixed value: the filter logic board sets it from the input line-to-line voltage it senses, and it varies with that voltage.
What to check
- Install a power monitor and use it to determine whether a power problem exists; this is the action the manual assigns to the message.
Setpoints and thresholds
- Filter DC link voltage setpoint — determined by the filter logic board from the input line-to-line voltage it senses.
- Setpoint value — the peak of the sensed line-to-line voltage plus 32 volts, and never more than 760 volts.
- The setpoint moves with the input line-to-line voltage.
- Trip point — the shutdown is generated when the DC link voltage on the filter falls to a point less than 60 VDC below this setpoint.
Questions engineers ask
What does FLTR LOW BUS VOLTAGE FLT mean on a YORK YK?
The message is generated when the voltage on the filter's DC link falls to a point less than 60 VDC below its setpoint. The harmonic filter raises its own DC voltage above the rectified line level by switching its IGBT's, which lets current move from the filter into the power line at the input peak.
Why does the FLTR LOW BUS VOLTAGE fault appear?
For occasional shutdowns the manual names a severe sag of the input line voltage as the likely cause. The setpoint itself is derived from the sensed line-to-line voltage — the line peak plus 32 volts, capped at 760 volts — so it moves with the supply.
What should I check first for this fault?
Install a power monitor and use it to determine whether a power problem exists; that is the action the manual gives for this message. If the trips are only occasional, a severely sagging supply line is the prime suspect.
What is the filter DC link voltage setpoint?
It is the peak of the sensed line-to-line voltage with 32 volts added, never higher than 760 volts, and it tracks the input line-to-line voltage.
Source
Written from the manufacturer's manuals for the YORK YK; every number and designation on this page is checked against them before publication. The row of the manual this message comes from:
All YORK YK messages: fault codes · YORK YK documentation · YORK manuals