Time to read: 5 min
While electric motors serve vastly different purposes, their core function remains the same—to convert electrical energy into mechanical energy. Numerous articles highlight the characteristics of each unique motor on the market, but they can be simplified into two overarching categories: AC (alternating current) motors and DC (direct current) motors.
每种类型都有自己的利弊，但本文旨在为您提供最佳使用AC或DC电机的清晰照片。让我们探讨它们各自转换电能，施工差异以及每种类型的最佳用例的方式。
Power
The glaring difference between the two types of motors is the power off which they run.
With AC electricity, or alternating current, the voltage reverses every half cycle, which in turn changes the direction of the current. This is done by alternating the polarity at each end of a wire. So, if you take the US standard of 120V/60Hz supply, there are approximately 120 half cycles per second.
随着直流电或直流电，电流的流量必须保持在单个方向（正为负），因此电压必须保持恒定，以便保持稳定的电流。您可以将DC电力视为带有明显标记的负极和正端子的电池。
AC Electricity for Motors
在使用交流电力的电线内，电子不会以单一方向以一致的速度行进，因为它们将与直流一起移动 - 它们只需来回蠕动并沿着能量传递（想起Newton’s Cradle).
交流电用于配电systems (power to your home/office), for the simple reason that AC is much more efficient when it’s transmitted through wires over a long distance, or for appliances requiring heavy voltage. Why is it better for these applications? Because the back-and-forth “wiggling” of electrons creates an electrical field, so a transformer can be used to kick up the voltage and still keep current relatively low.
By keeping current low, we reduce resistance through the wire, which equates to a higher efficiency. This correlation between current and voltage can be found in the Power Law: Power = Current * Voltage.
So what does all of that have to do with an AC motor? Well, basically, AC motors are great for high power appliances/machines that require little precision, like a blender or your washing machine. They’re objects you need to start, and they may ramp up or down in speed, but the difference between 400 RPM and 420 RPM probably isn’t critical.
DC Electricity for Motors
DC motors, on the other hand, are all about precision and stability, because the DC power supplying these motors comes in at a constant voltage. The electrons inside the wire can only travel in a single direction, and they do so at a normally steady pace.
Again, this is similar to the way a triple A battery will constantly give your electronics a supply of 1.5V (excluding losses) until they die. This is better when you have delicate circuitry/circuit boards or electronics that need a steady supply of energy to function properly, like a laptop.
But wait—if my home is supplying AC power, but my product requires DC power, what do I do?! Most electronics will have an AC to DC converter. That’s what that block is on the power cord for your laptop.
In fact, you can thank缝纫机上的转换器for the inspiration behind the band AC/DC’s name. With a DC motor, you can use a speed controller to adjust the voltage up or down, which will speed up or slow down the motor, but also maintain speed by monitoring the RPM of the motor and fine-tuning the voltage to ensure the motor remains steady.
建造
While the externals of both AC and DC motors may not be noticeably different, there are some fundamental differences internally that make them each unique. While you’re read the following information, it’s important to keep in mind that the difference is driven by their input/output: AC motors take in an alternating voltage for the sake of efficiency and power, while DC motors maintain a constant voltage for stability.
AC Motor Build
AC motors are very simple because the alternating current does all the work. By sending the current through a stationary wire that surrounds a shaft, you’re creating a varying magnetic field, which in turn will rotate the shaft.
Remember, AC electricity goes from “positive voltage” to 0 to “negative voltage” at double your frequency (Hz) every second. This means that with the U.S. standard of 60Hz, the current changes direction 120 times a second.
交流电机的简单性使它们持久，显着降低了机械误差的机会。效率和长的保质期之间的混合使它们成为您不想要太多能量损失的应用程序，并且不想不想不断更换电机（思考洗衣机）。虽然我依靠我的洗衣机足够，但如果它崩溃 - 不要告诉LG，我每年可能每年都要支付一个新的机器！
直流电机构建
DC电机的工作是提供稳定和精确的输出，这使其构造更复杂。返回到我们之前使用的电池示例，我们希望电池为我们的电路板提供一致的1.5V，而不是从+1.5到-1.5V的切换的裂缝一秒钟，第二次交流电源给我们。以同样的方式，为了使DC电动机转换为其提供的一致电压，我们需要将该电压精确地转换为机械能的电机结构。
为此，我们需要首先使用一些机械功能来创建移动电机的旋转。同样，这很简单地用交流电机，因为AC电力自然地来回摆动，这改变了磁场。通过DC，磁场将保持不变。
所以对抗,我们有几个旋转线圈在the center of a DC motor, which connect to a “commutator.” The commutator makes contact with stationary “brushes” of opposite polarities at the exact moment that it needs to change the direction of current to rotate the shaft.
这可能是显而易见的，但由于换向器和刷子之间的接触引起的摩擦，这里的主要缺点是效率损失。效率的损失以热量的形式留下，有时会使电机过载。
Function
If you’re sick of reading all the technical details and really just care about what motor works best for your needs, the long answer is, it’s really going to depend on your product and its functionality. The short answer is, here’s a basic list of functional uses for each type of motor:
Advantages of AC Motors
- Transfers energy more efficiently
- 寿命更长，失败的机会较少
- 产生较少的热量
- Better for high power applications (washers, refrigerators, machinery)
- 可以直接绑在家庭或办公大学插座中，没有转换器
Advantages of DC Motors
- Low electromagnetic interference (great for sensitive electronic devices)
- Stability for circuit boards and sensitive electronics
- 您可以在电池电量上运行您的产品
- 更好的速度控制
Main Takeaways
In reality, there will likely be several factors in your design that will drive the type of motor you choose. If you’re using电路板那batteries，并且需要微调速度控制，直流电机是去的方式。如果您正在寻求高功率，效率，持久，AC电机将完成诀窍。
