Single phase ac motor voltage speed, voltage torque relation
Electrical power: P = 1.732 * U * cos phi Torque: T = 9549 times P/n; Motor speed: n = 60f/p, p is the logarithm of the motor. Note: when the frequency reaches 50Hz, the motor is rated at the rated power and the frequency is increased, the power of the motor will not be increased, and the rating will be maintained. When the motor torque is below 50Hz, it is proportional to the frequency. When the frequency f reaches 50Hz, the motor reaches the maximum output power, which is the rated power; If the frequency f in 50 hz will continue to increase, the output torque is inversely proportional to the frequency change, because its output power is so big, you need to continue to increase the frequency f, then set into the calculation formula of the above analysis, the torque is obviously decreased. Speed and frequency is the same, because the power supply voltage unchanged, the frequency of change as a result of direct reaction speed change, compared to the same frequency increases, the speed increase, it decreases another also decreases. Let's look at these formulas for voltage analysis. The stator voltage of the machine: U = E + I * R (I for current, R for electronic resistance, E for inductive potential); E = k * f * X (k: constant, f: frequency, X: flux);
The asynchronous motor voltage is less than 360V and cannot function properly. The motor will not be able to switch to the power of the rotor, which will be converted into heat, which will seriously affect the life of the motor.
The voltage and the torque are the positive square T = constant c (c = the magnetic poles log P times the number of turns) times the stator voltage u squared/frequency f (the rotor resistance + leakage resistance) Low voltage variable speed slow torque smaller, the motor output torque is greater than the load torque operation is no problem, if the motor has long been at full load and overload operation will reduce its life, locked-rotor motor soon burned. The economic allowable words can be controlled by single phase variable frequency, and the variable frequency speed regulation is the constant torque output.
