電器知識問題(有關火牛)

火牛(Transformer)

Transformer have AC-DC,DC-DC,AC-AC,DC-AC 4 types,
almost transformer you found in your home is phone charger,

in your cellular phone charger,
always is AC220V transform to DC5V,
it is a type for AC-DC adaptor,
the transformer have decreases-voltage and increase-voltage,
if you stay in Taiwan(110V),but you have to use 220V-appliance,
you have to use a AC-AC transformer which input AC110V and output AC220V,

but if you stay in HK(220V),you have to use a 110V-appliance,you have to use a AC-AC transformer which input AC220V output AC110V,
some transformer can change the phases,
singal phase AC220V to 3 Phase AC380V
or 3 Phase AC380V to singal phase AC220V,

係唔係因為電壓過大d電器會過熱, 所以要降壓?
not yet,some device in the circuit board(resistor,capacitor) can not use 220V for conductor,
so it have to lower the voltage(many many reason that the voltage have to decreased),

點解有一d電器要有d又唔駛?
the heating element in 風筒 have to operated by high voltage,it not a LED Diode for 5V,
is also a high output power heating element.

2010-02-19 22:57:43 補充：
as I am said that,many heating element in electrical appliance is outputing the high power,

those"resistor" formed as the heating element,
you can think that a light bulb,

2010-02-19 22:57:47 補充：
light bulb use 220V to gives use heat and light by current via the heating element(resistor)
those heating element have amount of small resistance for 220V,but will not cause short circuit,

2010-02-19 22:58:25 補充：
yahoo真係好煩,要分開咁多次post -3-

火牛正確一D叫變壓器或整流器,降壓或加壓都可以,只可以將交流電變成直流電,但唔可以將直流電變交流電.
有D要用有D唔駛要分開黎講…
1.先講電子零件,只可以接受直流電和底電壓,有一D比較大ge電子產品如…LED電視機,本身LED只可以接受直流電和底電壓,但見唔到火牛係設計上問題.因為電視機本身而有火牛在電視機內所以唔駛.但當在日本自己買部電視機反香港,這時一定要有火牛.因為日本用110w而香港用220w, 電視機本身火牛只可以將110w變成適合電視機ge電壓量(如10w),但香港用220w,電視機本身火牛最多只可以變成20w.這時因電壓量過大會整壞電視機.所以要將220w先變成110w再變成變成適合電視機ge電壓量.
2.細ge電子產品如…手機,本身因為大細唔可以將火牛放在裡面,所以要火牛外路.
3.有D家庭電器如…風筒,可以唔用電子零件運用,又可以用交流電.所以只有設計成適合ge電壓袖唔駛用火牛.但當風筒係適合110w時,又要用火牛變成110w.
如果用過大電壓來開動電器,唔單只電器會壞,可能會有流電灼火.

因為香港供電係220V交流電, 有d電子零件要用比較低的電壓或直流電, 所以要用火牛, 降壓或轉做直流電