CORE PRINCIPLES
What to establish first
- Mechanical power is torque multiplied by angular velocity.
- At fixed power, lower speed requires higher torque.
- Each transmission stage introduces efficiency, alignment and service-factor considerations.
Motors & Power Transmission
Torque, speed, motor sizing and power-flow calculations.
MODULE OVERVIEW
Motors & Power Transmission in practical engineering work.
Power transmission connects a power source to a driven load through shafts, couplings, belts, chains or gears. The relationship between torque and speed is central, but transient torque and efficiency cannot be ignored.
DESIGN CONCEPTS
Terms worth checking
- Torque-speed relationship
- Efficiency
- Service factor
Common applications: Motor-driven machines · Gear reducers · Conveyors and mixers
KEY RELATIONSHIP
Power, torque and speed
T = 9550P/N
- T — torque, N·m
- P — power, kW
- N — speed, rpm
Use mechanical power at the shaft being checked; motor nameplate power may not be the transmitted power.
WORKED EXAMPLE
Known values → substitution → interpretation
- Known values
- P = 15 kW; N = 1440 rpm
- Method
- T = 9550 × 15 / 1440
- Interpretation
- The transmitted torque is about 99.5 N·m.
KEY DESIGN CHECKS
Confirm the conditions behind the number
- Define the governing load case, duty cycle and required design life before using a simplified relation.
- Use compatible units and material data for the actual condition, temperature and manufacturing state.
- Compare the result with strength, stiffness, fatigue, safety, serviceability and applicable-code requirements.
COMMON ENGINEERING MISTAKES
Keep the model within its scope
- Applying power, torque and speed outside the assumptions shown on this page.
- Using a nominal condition while a peak, alternating, transient or environmental case governs the design.
- Treating a calculated value as a final component selection without checking interfaces, tolerances and the current governing standard.
AVAILABLE CALCULATORS
Select a calculator
RELATED RESOURCE
Open Torque Calculator
Change mechanical power and speed to inspect torque and the live shaft view.
Open related resource →REFERENCES & LIMITATIONS
Use this content as a transparent starting point
ReferenceNIST SP 811 for units; the relation follows P = Tω with ω = 2πN/60.ScopeRelationships are presented for the assumptions stated on this page and linked tool.Design reviewCheck material condition, loads, environment and the applicable current code.SafetyResults are educational/preliminary and do not certify safety or compliance.
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