A trolley car collects traction power from an overhead contact conductor through a trolley pole or pantograph, while the running rails provide the return path to the substation. This calculator shows an ideal steady DC power balance from entered values.
Electrical checks for actuator-powered systems
This steady traction-power comparison does not size a linear-actuator power supply. For a separate actuator system, use actual startup, running and stall current together with duty cycle and wiring data.
When comparing a cylinder to an electric actuator, convert the discussion into stroke, force, speed, duty cycle, and installed length. Matching one specification is not enough.
The electrical margin should be based on worst-case motion, not a free-running bench test. Higher load increases current and heat, and long cable runs can reduce voltage at the actuator just when the motor needs it most.
- Size the supply for startup and stall current, not just running current.
- Check wire length, voltage drop, fuse rating, and controller output limits.
- Verify duty cycle so motor heat does not become the real failure mode.
For FIRGELLI actuator systems, start with the linear actuator power-supply sizing guide, then use the actuator duty-cycle calculator when the actuator cycles repeatedly. After the electrical limits are known, compare mechanical options in the FIRGELLI linear actuator range.
Trolley Car Interactive Calculator
Enter DC line voltage, motor count, output per motor and an overall efficiency. Results are ideal steady arithmetic, not measured starting, fault, feeder or thermal current.
Equation Used
- Entered motor outputs are simultaneous and identical.
- Entered efficiency represents all conversion losses between the DC line and motor output.
- A steady ideal single-path DC circuit is assumed, so supply and return current are equal.
- Auxiliary loads, acceleration, speed, tractive effort, controller states, regeneration, voltage drop, start current, faults, feeder protection, wire heating and ratings are omitted.
Overhead Supply and Running-Rail Return
The Federal Transit Administration describes traction-power distribution as feeder conductors to the contact system, vehicle collection by trolley pole or pantograph, and negative return through the running rails or a return conductor. U.S. Patent 400,724 documents a trolley wheel contacting an overhead wire and conducting power to the car motor.
What This Calculator Represents
The tool starts with entered output per motor and motor count. It divides their total by an entered aggregate efficiency, then divides ideal DC input power by entered line voltage. It does not calculate motor output from vehicle motion.
Ideal Steady DC Power Balance
ideal DC input = total output / eta
ideal line current = ideal DC input / Vdc
ideal return current = ideal line current
Worked Arithmetic Example
Four entered 40 kW motor outputs total 160 kW. At entered efficiency 100% and 600 V, ideal DC input is 160 kW and ideal line and return current are each 266.7 A. This is not a starting-current or equipment-rating prediction.
Model Boundary
- Calculated: an ideal steady power balance from entered values.
- Not calculated: tractive effort, speed, acceleration, motor curves, controller notches, regeneration, auxiliaries, voltage drop, starting or fault current, feeder protection, heating, equipment condition, capacity or safety.
Frequently Asked Questions
Is entered power electrical input?
No. It is interpreted as output per motor.
Does this predict starting current?
No.
Why are line and return current equal?
The model assumes one ideal steady series path.
Are auxiliary loads included?
No.
Does the tool size wire or feeder protection?
No.
Can it diagnose a trolley car?
No.
References
- Federal Transit Administration, Transit Asset Management Systems Handbook, section 3.4.2.2: contact systems, trolley poles or pantographs, and running-rail return.
- Federal Transit Administration, Project and Construction Management Guidelines: DC traction substations, overhead distribution and running-rail return.
- U.S. Patent 400,724, Trolley for electrical railways: overhead-wire contact and connection to the car motor.
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