# Motor Torque constant - with velocity constant

## Description

The constant K_v (motor velocity constant, or the back EMF constant) is a value used to describe characteristics of electrical motors.

Motor velocity constant, back EMF constant

Kv is the motor velocity constant, measured in RPM per volt (not to be confused with kV, the abbreviation for kilovolt). The Kv rating of a brushless motor is the ratio of the motor’s unloaded RPM to the peak (not RMS) voltage on the wires connected to the coils (the back EMF). For example, an unloaded motor of Kv, 5,700 rpm/V, supplied with 11.1 V, will run at a nominal 63,270 rpm (5,700 rpm/V × 11.1 V).

Motor Torque constant

KT is the torque produced per unit armature current. It can be calculated from the motor velocity constant Kv as shown here.

Related formulas## Variables

K_{T} | motor torque constant (N*m/A) |

π | pi |

K_{V} | motor velocity constant (Hz/V) |