Magnetics for UL 508A Panel Builders & Pump Stations
Control transformers, line and load reactors, output filters and harmonic filters for industrial control panels and water and wastewater VFD packages.
Parts That Fit the Panel, the Listing and the Specification
Panel shops build to a drawing, a schedule and a listing. Magnetics have to fit the backpanel, carry the markings the panel needs, and meet the engineer’s specification, which on municipal pump and lift station work often includes harmonic limits and long motor leads.
We help panel builders and integrators specify control transformers, drive reactors, output filters and harmonic filters, and we ask the manufacturer to confirm listing status on each quotation. See also harmonic filters and reactors.
Common Panel and Pump Station Needs
- ■ Control power transformers: Sized to the sealed and inrush VA of contactors, relays and solenoids.
- ■ Drive input reactors: 3% or 5% line reactors for VFD protection and harmonic reduction.
- ■ Pump VFD output filters: Load reactors, dv/dt or sine-wave filters for long leads to submersible and vertical turbine pumps.
- ■ Harmonic filters: Passive or active filters where the specification calls for IEEE 519 compliance.
- ■ Outdoor packages: NEMA 3R or 4X enclosures and ambient ratings for lift stations and skids.
Panel Magnetics at a Glance
| Component | Typical role | What to specify |
|---|---|---|
| Control power transformer | 120 V control power from line voltage | Sealed VA, inrush VA, primary/secondary voltages, fusing |
| Line reactor | Drive protection and harmonic reduction | Drive input amps, voltage, 3% or 5% |
| Load reactor / dv/dt filter | Motor protection on long leads | Drive output amps, lead length, motor insulation |
| Sine-wave filter | Very long leads or submersible pumps | Drive output amps, carrier frequency, lead length |
| Passive / active harmonic filter | Meet a TDD or THDi requirement | Total drive load, Isc at the PCC, generator operation |
What to send for a fast, accurate quote
- Drive make, model and amps for each motor
- Line voltage and control voltage
- Panel space, enclosure type and ambient
- Motor cable lengths, especially for submersible pumps
- Specification sections covering harmonics or filters
- Listing requirements for components
Quoting a Panel or Pump Station Package?
Send the drive schedule and specification sections. We will come back with options for each magnetic component.
Build a reactor spec sheet Contact usPanel builder and pump station magnetics: common questions
How do I size a control power transformer for a panel?
Add the sealed VA of everything energized at once, then check inrush: the transformer must hold voltage while the largest coils pull in, so it is sized against the combined sealed and inrush VA at an acceptable voltage drop using the manufacturer’s regulation data. Inrush, not sealed load, usually decides the size.
Do UL 508A panels need listed magnetics?
UL 508A panels are built from components that meet the standard’s requirements, which generally means listed or recognized components used within their ratings. Requirements depend on the component and the panel, so confirm with your UL 508A program. We ask manufacturers to state listing status on each quotation.
Why do submersible pump VFDs often need output filters?
Submersible pumps often sit at the end of long cable runs and many submersible motors are not inverter-duty rated. Reflected voltage peaks and fast voltage rise can damage the winding insulation, so pump manufacturers frequently require a load reactor, dv/dt filter or sine-wave filter. Follow the pump maker’s drive requirements.
Is a passive harmonic filter safe on a lift station with a generator?
It needs care. Passive filters can present a leading power factor at light load, which some generator voltage regulators handle poorly. Switched capacitor stages, active filters or a generator review are common solutions. Always state generator operation when requesting a filter.