Train Traction Power Calculator

Work out train traction power instantly with clear inputs, formula shown and shareable results.

About Train Traction Power Calculator

Rim power is tractive effort times speed, and input power is that divided by transmission efficiency. The second check is adhesion: tractive effort cannot exceed the coefficient of friction times the weight on driven axles, which is why locomotives are built heavy and why wheelslip control matters.

Formula

Traction power

P = tractive effort x speed / efficiency; adhesion required = TE / (driven mass x g)

Worked example

With the default values below, Train Traction Power Calculator returns Power drawn at the pantograph of 4,545.45. Change any input above and every figure here is recalculated in your browser.

Inputs used

Tractive effort at the wheel: 180 kN
Speed: 80 km/h
Transmission efficiency: 88 %
Mass on driven axles: 84 t

Results

Power drawn at the pantograph: 4,545.45 kW
Power at the wheel rim: 4,000.00 kW
Adhesion coefficient required: 0.2185
Adhesion assessment: Within normal adhesion limits

Step by step

1Values used
2Traction power
3Power drawn at the pantograph= 4,545.45 kW
4Power at the wheel rim= 4,000.00 kW
5Adhesion coefficient required= 0.2185
6Adhesion assessment= Within normal adhesion limits

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Rail results are planning estimates only. Verify against the infrastructure manager's rule book, approved braking curves and applicable railway safety regulations.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Rail results are planning estimates only. Verify against the infrastructure manager's rule book, approved braking curves and applicable railway safety regulations.

Frequently Asked Questions

What adhesion is achievable?

About 0.30-0.35 on dry rail with modern slip control, dropping to 0.15 or less on wet, greasy or leaf-contaminated rail.

Why do locomotives have a constant-power region?

Below a base speed the effort is limited by adhesion and motor current; above it, power is capped, so effort falls inversely with speed.