What does an inverter motor in a washing machine mean?

Increasingly, there are increasing concerns in the household appliance industry that have started implementing inverter motors in washing machines and launching extensive advertising campaigns. It is intriguing to ascertain whether the final consumer truly benefits from an upgraded product or if companies are merely streamlining their models by utilizing more innovative manufacturing technologies and capitalizing on the opportunity to earn additional income.

Figure 1: The advantages of purchasing an inverter washing machine

Design features of inverter machines

Washing machines equipped with an induction or collector motor use a belt for transmitting motion from the shaft to the drum. This "belt" drive is a key characteristic of these devices, indicating a complex design that includes pulleys for the drum and motor shaft, a belt, and fastening elements.

• The design features of inverter machines
• The device of the inverter motor
• The causes of malfunctions and diagnostics
• The pros and cons of new generation washing machines
• Should you buy an inverter model?
• In conclusion

Figure 2: A traditional motor with a pulley

However, a direct drive inverter motor operates differently. It does not require the aforementioned components as it is directly mounted onto the washing machine tank. The drum shaft serves as the motor shaft, resulting in a reduced number of bearings in the system. LG was the first company to introduce this type of design to its customers, along with a ten-year product warranty.

Figure 3: Attaching the inverter motor to the tank

Controlling the power section of the inverter motor is similar to controlling induction motors. This is because the inverter motor itself is a three-phase motor that is powered by direct current. The control system is based on a voltage inverter. This inverter can generate pulses with amplitudes ranging from zero to 120 V and with a frequency regulation of up to 300 hertz.

In order to make use of inverter motors, LG and other companies have started implementing technologies that utilize these motors. However, not all of them are directly driven. Many modern washing machine models are equipped with stepper (inverter) motors, which are traditionally located under the tank.

Device of the inverter motor

To gain an understanding of the reliability of the motor and its shaft design, it is beneficial to disassemble the "iron" parts. This will allow for accurate conclusions to be drawn regarding the quality of washing machines equipped with inverter motors. The motor mechanism comprises of:

1. A Stator, which is assembled with coils wound around cores made of electrical steel. The cores themselves are soldered into a polymer base that is directly attached to the tank (fixed part). There are a total of 36 coils, with their windings connected in a star pattern.
2. A Rotor that has a bowl-like shape, with its base made of steel. It features 12 permanent magnets that are affixed along the perimeter of the cylinder. The rotor is fastened to the drum shaft using a plastic bushing with splines, ensuring that the shaft does not become magnetized.
3. The Hall sensor is utilized for regulating the positioning of the rotor in relation to the coils.

Figure 4: The structure of the inverter motor

All functions of the washing machine motor are managed through a combination of opening, closing, and partially unlocking power switches composed of transistors. These switches alter the direction of current flow across the coil phases and adjust the magnetic flux within them. The inverter controls the operation of the switches using pulse width modulation.

Figure 5. Diagram of motor control

As evident from the blueprint, the motor is uncomplicated and lacks bearings; they are shared between the motor and the drum shaft.

Causes of malfunctions and diagnostics

Although washing machines with inverter motors have a simple design and seemingly reliable components, they are still susceptible to failure. The most frequent cause of these failures is a malfunction in the Hall sensor’s operation. In LG machines, this issue is indicated by the error code "SE" on the digital display.

Figure 6. Hall sensor

The issue can also be identified through the metallic rattling noise produced by the device. These symptoms are accompanied by the rotor coming to a stop and behaving incorrectly. The only way to confirm your suspicions is by replacing the potentially faulty component with one that is known to be in good working condition. The challenge lies in the fact that the motor diagnosis cannot be conducted outside the washing machine, unless the windings of the phases are tested using a digital multimeter.

Figure 7: Testing the coils using a multimeter

Faults in the inverter can also lead to operational failure, but it is impossible to detect such a problem without specialized equipment and expertise in electronics.

Pros and cons of new generation washing machines

What advantages can consumers gain from purchasing an inverter motor washing machine? These advantages include:

• A generous warranty period. LG offers a warranty of up to 10 years for machine performance.
• Noise and vibration reduction. Manufacturers guarantee that these machines operate almost silently, thanks to the absence of rubbing components like brushes and belts.
• Electricity conservation. The motor-to-drum energy transfer is highly efficient, resulting in minimal energy loss.
• Simple design. These machines have few components that can break, and replacement modules are readily available.
• No brushes. Unlike collector motors, which have limited lifespans, inverter motors do not rely on brushes, making them more reliable.

Whether to buy an inverter model?

Providing an unequivocal answer to this question is impossible as it largely depends on the individual’s needs when purchasing a washing machine. However, we can analyze the provided information and consider the following:

Why is silence important to you? For small apartments without the option of having a separate room for the appliance, a quiet washing machine would be an ideal choice. It allows you to focus on more important tasks without being distracted by the washing process.

Figure 8: A peaceful washing machine that won’t disrupt your sleep

1. What is the potential electricity savings? According to experts, it is no more than 5% as the majority of costs are attributed to heating water using heating elements, rather than the motor.
2. How long does the brush on the collector motor typically last for this particular model? Depending on usage intensity, the lifespan of high-quality brushes can be up to 10 years – a significant period of time.
3. Is a generous warranty on an inverter motor important? Absolutely, unless there are other factors at play that can damage the machine, such as hard water or sudden voltage fluctuations. These factors can undermine the efforts made by engineers to prolong the machine’s lifespan.
4. What does the simplified arrangement of the motor on the drum shaft provide? Firstly, it eliminates additional loads and extends mechanical lifespan. The only drawback is the close proximity of the electrical component to water. If the oil seal fails, there is a risk of winding burnout. These situations have already been encountered in practice.

Figure 9. Water-induced disturbance in the winding.

Conclusion

When selecting a washing machine for your home, it is crucial to consider all the parameters of the specific model. It would be disappointing to invest a significant amount of money in a modern appliance and not achieve the desired results when using it. Hence, before heading out to the stores, take the time to create a plan outlining the tasks you expect your future assistant to perform and familiarize yourself with the various models offered by manufacturers. Ultimately, the primary objective of a washing machine is to efficiently clean your laundry!

It is of utmost importance to have good washing quality, as depicted in Figure 10.