What is the relationship between torque and speed?
2 Answers
The relationship between torque and speed includes the following points: 1. The product of torque and speed multiplied by a constant k equals power. This means that when power is constant, speed and torque are inversely proportional. 2. For frequency converters, torque is higher at low speeds; for motors, torque is also higher at low speeds. 3. Torque represents force, while speed represents velocity. Greater force means more power, while higher speed only indicates velocity. Greater force allows screws to be tightened more securely, and higher speed enables faster movement, but only if the torque can overcome the resistance to speed increase until torque and resistance balance out for stability. 4. The voltage and frequency of motors are specially designed (including variable frequency motors). Motor speed regulation through frequency conversion affects torque. At high speeds, power increases while torque decreases. At low speeds, torque increases while power decreases. Medium-frequency motors perform poorly at low speeds but perform well at high speeds.
I once heard a mechanic make an analogy: the engine is like a person riding a bicycle, where torque is the strength with which you pedal, and RPM is how fast the pedals turn. High torque but low RPM (high torque, low revs) gives you strong climbing power but not much speed; low torque but high RPM (low torque, high revs) allows quick acceleration on flat roads but struggles uphill. There’s a simple formula: Power = Torque × RPM ÷ Constant. Car tuners understand this best—adjusting the ECU is about making the engine deliver maximum torque within a specific RPM range. For example, in a turbocharged car, you feel the strongest push at 3000 RPM when you floor it. When driving normally, you might notice the car feels powerful at low RPM but accelerates slowly, while at high RPM, it accelerates faster but consumes more fuel—this is the principle at work.
