Actuator Cable Voltage Drop and Loaded-Speed Estimate Calculator
Estimate actuator terminal voltage, cable voltage drop, cable heat loss, and idealized loaded-speed change from supply voltage, current, cable resistance, and nominal speed. The result is a preliminary engineering estimate, not a product rating or safety approval.
Calculate cable drop and loaded speed
Enter the measured or assumed inputs in one unit system. The calculator converts to SI internally, evaluates the stated model, and displays the result in the selected unit system.
Engineering visualizer
Schematic, not to scale. The drawing updates from the production calculation engine and labels the main outputs.
Calculator by FIRGELLI Automations.
Embed this calculator
When embedded on another page, the calculator shows only the working tool. FIRGELLI attribution, the visualizer, and the calculation-error report remain available.
What the terminal voltage and speed estimate mean
Drop is I times the round-trip resistance you entered. Terminal voltage is the supply minus that drop. The speed line is a proportion: loaded speed scaled by V_terminal / V_nom. Heat in the cable is I times the drop. On 12 V, a volt lost is not a rounding error. The ram at the far end is slower and weaker than the datasheet, which was taken at the nominal voltage.
This tool does not pick a wire gauge for you and it does not include starter inrush unless you typed that current. If two rams share a long homerun, they both see the sag. Thickening the pair, shortening the run, or moving to 24 V changes the inputs. Measure voltage at the actuator under load if the number looks ugly.
What This Calculator Calculates
What does actuator cable voltage drop and loaded-speed estimate mean? This quantity describes one specific part of the actuator design problem. It should be read as a model output, not as a complete product selection rule.
How To Interpret The Results
How should I interpret the actuator cable voltage drop and loaded-speed estimate result? A larger result means the checked effect is becoming more important and should be compared with product data, mounting limits, or the next design check. A smaller result does not prove the whole system is safe.
When Not To Use This Calculator
When should I not use the actuator cable voltage drop and loaded-speed estimate model? Do not use this model when the inputs are unknown, the mechanism is outside the stated boundary, or the decision depends on manufacturer ratings, fatigue, shock, compliance, or regulated safety approval.
Engineering model and calculation details
Estimate actuator terminal voltage, cable voltage drop, cable heat loss, and idealized loaded-speed change from supply voltage, current, cable resistance, and nominal speed.
The page separates the calculator result from product selection. It explains the inputs, limitations, interpretation, and next design checks so the result is not mistaken for a complete actuator rating.
Governing equations
| Quantity | Equation | Model meaning |
|---|---|---|
| Calculated cable voltage drop | V_drop = I R_cable |
Calculates calculated cable voltage drop for the stated simplified model. |
| Estimated actuator terminal voltage | V_terminal = V_supply - V_drop |
Calculates estimated actuator terminal voltage for the stated simplified model. |
| Idealized loaded-speed estimate at terminal voltage | v_est = v_nom(V_terminal / V_nom) |
Calculates idealized loaded-speed estimate at terminal voltage for the stated simplified model. |
| Cable heat loss at entered current | P_cable = I V_drop |
Calculates cable heat loss at entered current for the stated simplified model. |
Variables and canonical units
| Symbol | Variable | SI unit | Domain |
|---|---|---|---|
supply_voltage |
Supply voltage | V | finite engineering value in the documented model domain |
load_current |
Actuator load current | A | finite engineering value in the documented model domain |
round_trip_resistance |
Round-trip cable resistance | ohm | finite engineering value in the documented model domain |
nominal_voltage |
Nominal speed test voltage | V | finite engineering value in the documented model domain |
nominal_speed |
Known loaded speed at nominal voltage | m_s | finite engineering value in the documented model domain |
voltage_drop |
Calculated cable voltage drop | V | finite result from valid inputs |
terminal_voltage |
Estimated actuator terminal voltage | V | finite result from valid inputs |
loaded_speed_estimate |
Idealized loaded-speed estimate at terminal voltage | m_s | finite result from valid inputs |
cable_power_loss |
Cable heat loss at entered current | W | finite result from valid inputs |
Assumptions and boundary conditions
- Inputs represent one consistent operating condition.
- The model uses the simplified boundary stated on the page.
- The model begins and ends at the user-defined actuator or mechanism boundary.
Limitations and omitted checks
- The result depends on user-entered values and simplified boundary conditions.
- The model does not replace FIRGELLI product data, installation review, endurance testing, or a qualified engineering review.
- Shock, fatigue, misalignment, mounting strength, and controller behavior may govern before the calculated value.
Worked example
12 V, 10 A, 0.15 Ω round-trip, nom 12 V at 20 mm/s. Drop = 1.5 V, terminal = 10.5 V, speed ≈ 17.5 mm/s, heat = 15 W. The datasheet speed was at 12 V at the motor, not at the supply.
Related checks: power-supply sizing calculator, wire-gauge voltage-drop AWG calculator, open-loop drift and skew calculator.
What this model evaluates
| Mode or effect | Status | Disclosure |
|---|---|---|
| calculated quantity | evaluated | The named output is evaluated for the stated model. |
| manufacturer rating | not evaluated | The result is not a manufacturer product rating. |
| installation detail | not evaluated | Mounting, alignment, shock, fatigue, and environment require separate review. |
Common mistakes
- Treating a simplified estimate as a manufacturer rating.
- Mixing units or entering values measured at a different operating point.
- Ignoring mounting, alignment, shock, duty cycle, or controller limitations.
- Failing to compare the result with the next logical FIRGELLI design check.
Engineering references
- OpenStax. University Physics Volume 2 - Direct-Current Circuits. Rice University, 2016. Supports: Ohm-law and DC circuit relationships used for voltage drop and power loss.. Accessed 2026-07-28. Source.
- National Institute of Standards and Technology. Ampere and Electrical Measurement Context. National Institute of Standards and Technology, Accessed 2026. Supports: Electrical unit consistency for current, voltage, resistance, and power relationships.. Accessed 2026-07-28. Source.
- National Institute of Standards and Technology. NIST Guide to the SI. National Institute of Standards and Technology, Accessed 2026. Supports: SI unit definitions and unit-consistent engineering calculation display.. Accessed 2026-07-28. Source.
Author, validation, and review status
Author: Robbie Dickson
Author profile: Robbie Dickson prepares FIRGELLI actuator education and calculator content for product users and engineering teams.
Engineering model type: DC cable voltage-drop and proportional loaded-speed estimate
Validation: The production JavaScript engine is compared with a separately written Python oracle across known-answer, SI/imperial-equivalent, boundary, invalid-input, and randomized cases.
Questions about this calculator or found an error? Message our engineering team.
