From air conditioning and agricultural equipment to toothbrushes and wind-up cars, we are surrounded by motors. However, motors are not one-size-fits-all. It is essential to choose an appropriate motor for your product that fits your budget and performance requirements.
Types of Motors – AC vs. DC
All motors convert electrical energy into mechanical energy. The two main types of motors are AC (alternating current) and DC (direct current). In DC motors, the electric current maintains the same voltage, while in AC motors, changing magnetic field polarity causes the current to switch directions periodically.
When choosing a motor, consider your power source. AC motors cannot convert DC power to AC power. Any product running on batteries, which produce DC, must also have a DC motor. On the other hand, some DC motors can convert AC power to DC power with commutation, which prevents polarity reversal.
Current, voltage, and velocity are critical factors to consider when choosing a motor for your product. It is important to know the capabilities of each one and what your product can handle.
DC Motors – Brushed vs. Brushless
The two main categories of DC motors are brushed and brushless. Brushless motors are more efficient, have a longer lifespan, and require less maintenance than brushed motors, but are also more expensive.
Brushed DC Motors
In brushed motors, the commutator is rotated by brushes that control current polarity. Brushed motors are suitable for applications that require low to moderate power and efficiency. Brushed motors can also be controlled with simple electronic circuits and are a good choice for products requiring a low-speed, high-torque motor. However, brushes wear out over time, meaning these motors require more maintenance and have a shorter lifespan than their brushless counterparts. It is important to know the amount of power and speed regulation your device needs to work effectively, as it dictates which type of brushed motor is best for your product.
Types of Brushed Motors
- Shunt Wound: These motors have a medium-high starting torque without a reduction in speed. They are usually used in industrial applications that need to keep a stable speed, such as winding or unwinding machines.
- Series Wound: Series wound motors have a strong starting torque but have poor speed regulation. They are well-suited for applications that need a lot of power, such as trains and hoists.
- Compound Wound: Compound wound motors have both shunt and series windings. Because of this, they have the strong torque of series wound motors and the speed regulation of shunt wound motors, making them a common choice for industrial applications like conveyors and elevators.
- Permanent Magnet: Permanent magnet motors can run on both alternating and direct current. They regulate speed well and are used in low-horsepower applications. They are more efficient and compact than other motors, which use electromagnets. Pivot International company DCI designs and develops permanent magnet motors used in variable speed pumps for above-ground pools.
Brushless DC Motors
Brushless motors can operate at high speeds with precise speed and torque control, making them popular for high-speed and industrial applications. They also operate smoothly and quietly. Products where noise reduction is important, such as air conditioners, use brushless motors. American houses generally run on AC power, so brushless motors in air conditioners convert the AC to DC.
Our subsidiary Castle Creations is an expert in brushed and brushless DC motors for various applications, including firefighting helicopters and RC cars.
AC Motors
AC motors are powered by an alternating current that periodically changes direction. In AC motors, voltage changes periodically, making them more energy efficient than DC motors, which maintain voltage levels. Generally, devices with AC motors need to be plugged into a power source to run, though there are exceptions for AC motors that act as generators or have an inverter added to convert DC power to AC power.
Like brushless DC motors, AC motors require less maintenance than brushed motors because brushes need to be maintained and replaced over time. AC motors are often the most cost-effective option, as they are simpler than DC motors. However, DC motors have higher starting torque, providing quick acceleration.
Consider the power and precision you need when deciding whether to use an AC or DC motor. For applications requiring high precision, such as robotics, DC motors are usually the correct choice. Most household products use AC motors since they are cheaper and can be integrated easily into the existing power grid without needing current conversion. The two main types of AC motors are synchronous and asynchronous.
Types of AC Motors
Synchronous: Synchronous motors’ speed is proportional to the frequency of their voltage. These motors have high torque and efficiency and can be used as generators. However, they are also complex and expensive and, unlike DC motors, require separate starting devices.
Asynchronous: Also known as induction motors, asynchronous motors create torque from electromagnetic induction. Induction motors are lower power but are also simple, reliable, and cost-effective. Single-phase induction motors are used for lower-voltage applications, such as household appliances. Three-phase induction motors have a higher starting torque and are used in industrial applications.
Integration With Your Product
Ultimately, voltage, power, and performance are the main factors to consider when choosing a motor. Size is also critical, as a motor that is too small may not reach the desired output. Motors that are too large are heavier and more expensive.
Another element to account for is interaction with other components. Treadmills have speed controls and displays. They must be able to support the weight and impact of a human for extended periods. Treadmills with an incline function have a second motor to ensure that they can handle the power needed.
Choosing the right motor for your product can be a difficult task. Partnering with a motor control design company is the best way to ensure your product is effective and successful.
Pivot International has extensive experience in motor control design and build. Our cross-functional team has developed AC and DC motors for various applications. The addition of Castle Creations and DCI to the Pivot family of companies has expanded our motor expertise. To learn more about how we can help with your motor selection and design, contact our team to get started.
