Many applications need the speed adjustable AC motor since different conditions need different speeds. The common sense is in normal weather, you need to set the fan in a regular speed, but in very hot weather, you need the fan to be faster. If you stick with the constant speed, you likely feel too hot or too cool and this will make you feel uncomfortable. In order to make the AC motor speed adjustable, an ac motor speed control is needed. Fortunately, you will not get a problem to find it in the market for various types of speed controller for AC motor are available. You can buy it from land-based provider or buy it online from online provider worldwide.
AC motor is a motor that uses alternating current power supply. Similar to the DC motor, different voltage will influence the speed of an AC motor, so a variable resistor or variable transformer which can change the voltages can be used to control the speed. However, the method is not suitable for various motors when dealing with the accuracy issue. Even more, loss of power makes the methods energy inefficient and become another problem with the motor. Although those methods are low cost and many people still use them due to the budget, many applications need a more accurate and energy efficient ac motor speed control.
In order to get more accurate speed control, a frequency control is used. Frequency has a link to voltage so a change in frequency used in the motor will change the voltage, and the speed of the motor will change as well. An inverter that can control the frequency is a better choice if you want to control the speed of an AC motor. In the past, the inverter was big problem due to high cost and limited device supply, but now the inverter is more affordable and widely available in the market. When you hear or read VFD, you will find it a better ac motor speed control with energy efficient and high accuracy.
The phase control device is another way to control the speed of an AC motor. When triggered, the device will conduct current in bidirectional and you can control the current that flows to the load. Current has a link to voltage that will influence the speed, so controlling the pace will help you control the speed of an AC motor. The device is a good option since it is an energy efficient ac motor speed control and the accuracy is better. Using the phase control device is suitable for a single-phase induction motor.
VFD is the most common speed control of an AC motor, especially for the 3-phase induction AC motor. It is also very common for brushless DC-motor that the principle of working is similar to the 3-phase AC motor. VFD is standing for Variable Frequency Drive that the device can drive variable frequency that will influence the voltage and make a speed change. Some people simply call VFD an AC inverter and the other call it ASD or adjustable speed drive. VFD is energy efficient with an ability to work in low speed as the additional advantage. VFD downsides are potential bearing noise, expensive cost, and the size can be too big.
For phase control device, the most common ac motor speed control is TRIAC control. The technology is best to be used in a single-phase induction motor. TRIAC control is a low cost option that will eliminate the money problem if cost is your most concern. For another application, TRIAC control is also very common for light dimmer control. When you compare it to VFD, TRIAC can be more energy efficient when operated at high speed since TRIAC can not work well at low speed. Another downside of TRIAC is a potential non-linear control curve.
As the technology develops, you may find the ECM motor as an AC motor in the market and the new technology tends to grow fast. For this technology, those speed controls above are not suitable. For the ECM motor, you will need an ECM control to control the speed. The speed control is the most energy efficient which has its best accuracy and able to work at low speed. However, as it is a new technology, the cost is the most common problem and you may not find the size you need.
In your daily life, you will find various applications of ac motor speed control. Ventilation is the most common you will find since your ceiling fan or attic ventilation may use it. Since over heat can damage the electronic device, the air mover that controls the temperature will need a speed control. Therefore, the electronic cooling appliance is the next common application. In special places, you will find more applications of speed control such as for controlling the small AC pumps, controlling the fan speed in room humidity, and regulating the speed of air mover at HVAC application. You may not realize it but if you pay attention, you will find more application of AC motor with a speed control inside it.