Home > categories > Machinery & Equipment > AC Motor > Relation of voltage, speed, voltage and torque of single phase AC motor
Question:

Relation of voltage, speed, voltage and torque of single phase AC motor

Relation of voltage, speed, voltage and torque of single phase AC motor

Answer:

The voltage and torque is constant (c= C T= square poles P * * * the number of turns of the stator voltage of U / L) * f (frequency rotor resistance + leakage resistance)The voltage is low rotational speed torque, output torque of the motor load torque is not greater than the operation of what the problem is, if the motor in full load and overload operation will reduce the service life of the motor, the motor blocking words soon consumed.If the economy allows, you can use single-phase frequency conversion speed control, variable frequency speed regulation, rated frequency speed regulation is constant torque output.
Of course, if the power frequency is constant, the motor torque must be proportional to the voltage, but it must be before the motor reaches the rated output torque.
The speed and frequency are the same, because the supply voltage is constant, the frequency of the change, the result of direct reaction is the same speed change, frequency increase, speed also increased, it minus the other also reduced.On voltage analysis, look at these formulas.Motor stator voltage: U = E + I * R (I is current, R is electronic resistance, and E is inductive potential);And E = k * f * X (k: constant, f: frequency, X: flux);For asynchronous machines, T=K * I * X (K: constant, I: current, X: flux);It is easy to see that the frequency of F changes, is also accompanied by the change of E, voltage of the stator should also change, frequency control methods commonly used in fact is that, when the frequency changes, the inverter output voltage, also is the increase in voltage at both ends of the stator is changed, is proportional to the this is the ratio of frequency conversion constant V/f. Analysis of the three equations can also be used in front of the same results can be obtained.
Motor power: P=1.732 * U * I * cos PhiMotor torque: T=9549 * P/n;Motor speed: n=60f/p, P for the motor pole count, such as four motors p=2;Note: when the frequency reaches 50Hz, the motor reaches the rated power, and then increases the frequency, the power will not increase, and will maintain the rated power.The motor torque is less than 50Hz, is proportional to the variation with frequency of F; when the frequency reaches 50Hz, the motor reaches the maximum output power is rated power; if the frequency of F in 50Hz and then continue to increase, the output torque is inversely proportional to the frequency change, because its output power is so big, you have to continue to increase the frequency of F, then the formula set in the above analysis, the torque is obviously reduced.

Share to: