Mrkuple Blog

Speed AC motors: increasing the number of poles of a toggle switch motor influences the speed of the engine, which is determined by the formula:
F= P * F (n/60)
Frequency at which an engine works is given by the number of pairs of poles P multiplied by engine speed in revolutions per minute spot (rpm) divided by 60.
Therefore, if you want to know what rpm speed operating a motor simply transform previous formula:
n = (60.F) / P
The number rpm, an engine that turns depends on the operating frequency of 60 times, divided all by the number of pole pairs having the motor.
Switching toggle switch poles.
Consequently, the speed of a motor does not depend on any operating voltage, and as the value of the frequency is unchanged, to change the motor speed can only be done by changing the number of poles on the engine of two-speed motors, therefore, take shots intermediate pole pairs, the terminal box, so that, with the help of special switches, to alter the input and output current to each pair of toggle switch motor poles.
Consequently, the speed would be affected by the position of the switch poles. All two-speed motors, take in the terminal box, double the connections of a single speed motor.
Table I shows how the European engine, working at a frequency of 50 Hz, are slower than those in the Americas that work to 60 Hz, also reported that for higher wind speeds, for example, those required in the radar, which employs 400 Hz frequency with which obtains very fast rotor engines.
The more speed an engine have, and therefore be less than the number of poles, the cheaper the price will be the engine, then dimensions of toggle switch are also lower.
At the same speed engine size increases with power to develop.
2. Frequency variations
Today it is possible to change the speed and the engines, without altering the number of pairs of poles, in the formula shows that if the frequency value instead of having a fixed value of 50 or 60 Hz , could change this value, then get different values of the number of rpm, the toggle switch engine. This is done using variable speed drives static.
Small electronic devices are sandwiched between the toggle switch and the engine with which you can easily act on the frequency to vary the engine speed without complicated switches poles.
Figure 1, can be a variable rate, applicable to three-phase motors with squirrel cage rotor, and a power between 370 W and 17 KW.
4. OPERATION SPEED CONTROLLER
Phase alternating current is rectified and converted into direct current, and then, in an inverter circuit, is converted back to alternating phase. For the frequency can be variable, do not get to change at all in a linear stream, a part of this current input is filtered through a circuit that regulates the output.
The relationship between voltage and frequency should remain constant for the motor torque to retain its important, regardless of speed. This means that changes the voltage and frequency in the same proportion.
Figure 2 shows in block diagram the four main toggle switch circuits carrying a variable speed drive rectifier, DC link, inverter and control toggle switch circuit.