Reading a motor datasheet
The handful of numbers that tell you almost everything about a traction motor.
You'll learn
- Explain reading a motor datasheet at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real drive unit
Overview
A motor datasheet looks intimidating at first, but a small set of figures — peak and continuous torque, peak and continuous power, base speed and maximum speed — tells most of the story.
In depth
| Spec | Typical value | What it tells you |
|---|---|---|
| Peak torque | 310 Nm | Best acceleration, sustainable only briefly |
| Continuous torque | 180 Nm | What the motor can hold indefinitely without overheating |
| Peak power | 150 kW | Peak torque × speed at the top of the constant-torque region |
| Base speed | 4,500 rpm | Where the motor transitions from constant torque to constant power |
| Max speed | 16,000 rpm | Upper limit set by mechanical strength and field-weakening capability |
Calculator
Motor Power Calculator
Mechanical shaft power from torque and rotational speed.
Nm
rpm
%
Shaft power
194.8kW
Shaft power
261hp
Electrical input
207.2kW
Formula
P (kW) = T (Nm) × n (rpm) ÷ 9550Power is torque times angular velocity. Angular velocity in rad/s is 2πn/60, and dividing by 1000 for kilowatts collapses the constants into 9550.
Example: 310 Nm at 6,000 rpm → 310 × 6000 ÷ 9550 ≈ 195 kW.
- Below base speed the motor is torque-limited; above it, power-limited.
- Electrical input power is shaft power divided by efficiency.
- Peak power is thermally limited and can rarely be held for more than 10–30 seconds.
Quiz
Datasheet check
- 1
What happens at base speed?
- 2
Peak torque can usually be sustained indefinitely.
Key takeaways
Remember this
- Peak and continuous ratings answer different questions — burst versus sustained performance.
- Base speed marks the transition from constant torque to constant power.
- Always check continuous figures before sizing a motor for real-world duty.
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