引用自友站關於正弦波和模擬正弦波的一段文章
(出處:http://www.mobile01.com/topicdetail.php?f=444&t=1252264&p=3#15029530)
Q: What is the difference between sine wave
and modified sine wave?
A: Alternating current (AC) has a continuously varying voltage that swings from
positive to negative. This has great advantages in power transmission over long
distances. Power from your power company is carefully regulated to be a perfect
sine wave, because that is what naturally comes out of a generator, and also
because sine waves radiate the least amount of radio power during long distance
transmission.
On the other hand, a sine wave is expensive to make in an inverter, and many
sine wave techniques use heavy, inefficient transformers. The most inexpensive
way to make AC is to switch the DC on and off--a square wave. A modified sine
wave is scientifically designed to simulate a sine wave in the most important
respects so that it will work for most appliances. It consists of a flat
plateau of postive voltage, dropping abruptly to zero for a while, then
dropping again to a flat plateau of negative voltage, back to zero for a while,
then returning to the positive voltage. This pause at zero volts puts more
power into the 60HZ fundamental than a simple square wave does, so it is called
"modified sine wave" instead of "square wave."
白話的講,正弦波inverter對電力供應最重要的一點,就是不會產生壓降,
也就是說,不會110v在負載(loading)後,電壓迅速下降,造成供電不穩,
進而影響電器壽命(特別是有馬達,以及對電流品質很要求的),
另外,也可讓電力在轉換中產生的無謂損耗達到最低,
且雜訊也比模擬正弦波來的少很多,這樣的雜訊消耗,差別超過20%以上,
一般市電也是用正弦波進行傳送,正弦波inverter用料差很大,也因此貴很多。
其實,楔石就有賣模擬正弦波的轉換器,有興趣的可以買來試試,
如果理論上模擬正弦波的就可用來推棚燈,那裡就有賣1000w,
但事實上要推棚燈是推不動的,而一些救車用電包,更是頂多幾張就KO了,
這些,都已經有攝影師測試過了,其實都是因為壓降和消耗電流過大所導致。
如果有人能找到可用又比較便宜的模擬正弦波inverter,
懇請出個聲,提示個品牌和型號,並請分享實測結果,
相信很多人會很感激的,因為不會有人老愛背很重的器材,
或是買貴森森的進口電源供應器,手上光是電力這樣測試,就花掉六七萬了,
只憑理論是不太夠的,大家需要能放心帶出門的東西才是真的。
至於國外所賣的電源供應器,看來是真的不錯,也非常心動,
但是重量達27.694公斤(61lbs),這樣自己做出來的重量差不多,
單買價格(約NT.16,500)也是和自己做出來的差不多,
但運費和關稅加一加應該就兩萬了,而且應該要用船運,無法空運,
有輪子是很方便,但自己做的當初就是故意不要將輪子做在上面,
為什麼呢?因為常遇到的地形都不好,輪子壞了就不知道該怎麼辦了,
而電池用久了總是會老化(應該比inverter快吧?)
能否靠自己就輕鬆拆換電池也是需要考慮的,
綜合以上考量,這就是為何還需要自己辛苦來回討論設計製造了。
總覺得這篇討論非常實用,外拍電源一直是商攝很需要克服的一環,
大家有什麼好的想法和建議,繼續討論,看看有沒更好的方案,
目前重量還是不小的問題,但這和能供電多久也有很大的關係,還在想有沒好辦法。