DSL Busbar Voltage Drop Calculator

Estimate whether a proposed EOT crane DSL/busbar rating and feed arrangement may create excessive voltage drop for one crane or multiple cranes sharing the same bay.

Enter DSL Details

Use vendor data where available. If not available, use this as a first-pass estimate before asking the vendor to confirm the exact design.

Volts, 3-phase system

Total busbar length in meters

Center, dual, or multiple feeds reduce the longest current path

Used when individual currents below are blank

Cranes sharing the same DSL/bay

Optional. Enter different crane currents in amps, separated by commas. When filled, this overrides current per crane and number of cranes.

Use 1.0 for worst case, 0.7 when not all cranes run at full load together

Adds buyer-side allowance before comparing busbar rating

Used only when multiple feed points is selected

Use the offered DSL/busbar rating

Percent limit for warning

When to Worry

  • Long runway with only one end feed.
  • Two or more cranes sharing one DSL with end feed only.
  • High current cranes on low-rated busbar.
  • VFD trips or contactor chatter near far end.
  • Vendor cannot explain voltage drop basis.

How to Improve

  • Increase busbar current rating or conductor size.
  • Use center feed or additional feed points.
  • Reduce joint resistance with better installation.
  • Confirm actual conductor data with the supplier.

Next Step

Use this result while comparing quotations and ask vendors to confirm their calculation, BOM, and feed arrangement.

Open DSL Toolkit

Related DSL / Busbar Guides

Current Rating Voltage Drop Guide Multiple Cranes Collector Shoes

For electrical engineers and crane buyers.

Engineering notes

What this DSL estimate includes

Purpose: screen busbar current utilization and approximate three-phase voltage drop for one crane or several cranes sharing a bay, including simple end, center, dual or multiple-feed layouts.

Inputs explained

Voltage and runway length
Set system voltage and physical DSL length.
Feed arrangement
Approximates the longest current path: full length for end feed, half for center/dual, or a segmented path for multiple feeds.
Crane currents
Use one repeated current or enter different currents; individual values override crane count.
Simultaneity and margin
Convert connected current into the design current used by the estimator.
Material, rating, power factor and limit
Select an internal resistance value, calculate drop and compare with the user-entered percentage limit.

Formula basis

connected current = sum of crane currents

design current = connected current x simultaneity x safety margin

effective path = L, L/2, or L/(feed points + 1) depending on selected feed arrangement.

voltage drop = sqrt(3) x design current x R x path(km) x power factor

utilization = design current / selected busbar rating x 100

Worked example

For 415 V, 60 m end feed, one 80 A crane, 0.70 simultaneity, 1.10 margin, copper 100 A busbar, 0.85 power factor and the tool's 0.18 ohm/km resistance: design current is 61.6 A, estimated drop is about 0.98 V or 0.24%, end voltage is about 414 V, and current utilization is 61.6%. Actual manufacturer impedance may produce a different result.

Assumptions

  • Balanced three-phase load.
  • Internal table uses typical resistance by material/rating.
  • Center and dual feed use half-length worst path.
  • Multiple feeds divide length into equal approximate segments.

Results interpretation

  • Check drop percentage and current utilization together.
  • Use 1.0 simultaneity for a conservative all-cranes case.
  • Compare end versus center/additional feeds.
  • Ask vendors to show the exact crane-position case used.

Limitations

  • No conductor reactance or harmonic calculation.
  • No temperature correction, joint or collector contact resistance.
  • No feed-cable impedance, starting-current or VFD transient model.
  • No exact load-sharing analysis for dual or multiple feeds.

Related standards to check

Voltage-drop limits and conductor sizing must follow the project electrical design basis and local code.

  • IEC 60204-32:2023 - electrical equipment and external power/control feeders for hoisting machines.
  • Applicable electrical-installation and conductor-bar product standards required by the jurisdiction and contract.
  • Manufacturer resistance/reactance and temperature data for the exact offered system.

FAQ

How should different crane currents be entered?

Enter comma-separated currents. Their sum replaces current-per-crane and crane-count inputs.

Does center feed always halve voltage drop?

It halves the modeled maximum path, but actual crane positions, cable impedance and load sharing still matter.

Is current rating enough to select DSL?

No. Check voltage drop, short-circuit protection, joints, collectors, environment, expansion and mechanical installation.

Next action: request the vendor voltage-drop sheet

Ask for conductor impedance, temperature basis, feed cable, joints, collectors, crane positions, simultaneity, starting case and end voltage for the offered layout.

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