熱水器是現在家庭必備的電子產品之一，最初是以燒乾柴的方式去加熱熱水，之後轉變為瓦斯熱水器、電熱水器、太陽能熱水器及鍋爐等方式，其中儲能式熱水器(熱泵式、太陽能熱水器)的市場發展最為看好，而上述的熱水器都有各自的優缺點，如瓦斯熱水器效能太低、電熱水器所需能量太高、太陽能熱水器無法瞬間加熱等，造成以上熱水器的限制。瞬熱型電熱水器為電阻式加熱，將發熱體放置於水桶內部，經由熱傳導方式直接進行加熱，此方法水與電有直接傳導之可能，經長時間使用有危險性。而本論文將採用感應加熱原理設計瞬間加熱的加熱系統，有效的將水與電分開，效率相對一般儲能式熱水器要高，提高了使用上的安全性，也具有一般電熱水器之優點。
感應加熱於民間及業界的應用也越來越多，主要因其特點有：
1. 傳熱不需介質，不會受天氣因素影響加熱效率。
2. 利用電能轉換為熱能，不過有過多的廢氣、廢熱等。
3. 加熱迅速，可用高功率密度之電流，快速完成加熱。
4. 加熱能量為加熱物件內產生，能量損耗較低。
　　本研究以感應加熱方式設計電熱水器，主要電源供應電路其架構為半橋式諧振電路，功率為3.8kW，輸入電壓為220V，輸入電流為17.5A，加熱效率為75%，且具有零電壓轉換之情形，以此電源供應電路，配合溫度控制、頻率自調、保護電路及水桶設計等，完成感應加熱熱水器系統。電源供應電路設計上需注意輸入電源之雜訊，驅動開關之訊號不重疊，導致開關直通，開關切換上的特性等，減少電路上功率的消耗，再藉由自行開發之溫度控制PID控制器進行溫度控制，穩定出水水溫。

Water heater is one of the products that each family must have now, which can be divided into storage type water heater and instant hot water heater. In this thesis, an induction heating water heater was developed. The system had power supply system, control system, protecting system, and heating bucket. The power supply develop by half-bridge circuit. Zero-voltage-switching operation of all switches can be achieved with two power switches. The power supply system with maximum power capability of 3.8kW use electric power with 220V. The control system included the temperature controller and the power switch. The temperature controller use PID theory to work. The Protect system included switch’s temperature, switch’s current, and water flow. Which make sure the water heater can work safely. The self-tuning circuit measure resonant frequency of the power circuit, to maximum the power of the system. The heating bucket is made by SUS444. The material is magnetic material, and Corrosion-resistant material. The water heater can increase 3.7oC when flow rate is 182 mL/s. The power efficient is 75%.

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