Why 60 hertz or 50hertz

Thread Starter

donskiter

Joined Nov 17, 2006
29
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Hello everyone...

Good day. Im noticed some devices like motors, appliances or any electronic devices used different rated of hertz liked our TV used 60 hertz some TV used 50 Hz others rated 50~60. I know that every countries have there own standard of hertz...My question is there any effect with the performance of a motor or any kind of electronic devices if they used with different rate of hertz. Is the rate of hertz has effect the design, size of the wire and number of turns of wire..etc.. when creating a new electronic devices...

Don
 

Gadget

Joined Jan 10, 2006
614
Anything with a synchronous motor or uses the mains frequency as a reference (ie some digital clocks) will work incorrectly with the wrong mains frequency.
Most transformers work just fine at either 50 or 60 hertz.
Any AC motor must be monitored to check it doesnt run too hot at the wrong frequency (speed), and that the speed is still OK for the job it is being used for.
 

Papabravo

Joined Feb 24, 2006
14,412
----------------------------------------------------------------------
Hello everyone...

Good day. Im noticed some devices like motors, appliances or any electronic devices used different rated of hertz liked our TV used 60 hertz some TV used 50 Hz others rated 50~60. I know that every countries have there own standard of hertz...My question is there any effect with the performance of a motor or any kind of electronic devices if they used with different rate of hertz. Is the rate of hertz has effect the design, size of the wire and number of turns of wire..etc.. when creating a new electronic devices...

Don
I don't know about 50-60Hz., but I do know why aircraft power systems run at 400 Hz. One word - weight.
 

Dave

Joined Nov 17, 2003
6,970
An explanation of some of the issues relating to spped control with AC motors is covered in Volume 2:Chapter 13 of the on-line textbook:

Modern solid state electronics increase the options for speed control. By changing the 50 or 60 Hz line frequency to higher or lower values, the synchronous speed of the motor may be changed. However, decreasing the frequency of the current fed to the motor also decreases reactance XL which increases the stator current. This may cause the stator magnetic circuit to saturate with disastrous results. In practice, the voltage to the motor needs to be decreased when frequency is decreased.

Conversely, the drive frequency may be increased to increase the synchronous speed of the motor. However, the voltage needs to be increased to overcome increasing reactance to keep current up to a normal value and maintain torque. The inverter (Figure http://www.ibiblio.org/obp/electricCircuits/AC/AC_13.html#02480.png) approximates sinewaves to the motor with pulse width modulation outputs. This is a chopped waveform which is either on or off, high or low, the percentage of “on” time corresponds to the instantaneous sine wave voltage.
I will need to chase up why this chapter has not been added to AAC.

Dave
 

wireaddict

Joined Nov 1, 2006
133
Because some countries use 50 Hz and others use 60, most AC devices specify which frequency they're rated for, including both. AC induction and synchronous motors are frequency-dependant; the speed [rev/min]=120 X freq./the no. of poles. TVs, monitors and other devices which use power line frequency for sync and timing functions instead of internal crystal oscillators are likewise frequency-dependant.
 
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