Updated: Aug 1, 2020
This is an educational blog series for hand dryer buyers about the important factors to keep in mind while buying hand dryers.
In this first part of the blog series, we will concentrate on the motors. The motor is the heart of the hand dryer. Motor plays a vital role in its performance and usually is the costliest part of the hand dryer. Having a heavy duty motor is vital for long operational life of the hand dryer as a bad quality motor can result in high repairing costs and down time and frustration for users.
There are many hand dryers available at different price points from Rs 2000 to Rs 1,00,000. What makes some hand dryers so cheap and others so expensive? What is the difference between these hand dryers? Usually, among other reasons, the major difference is the motor.
Lets have a look at the different types of motors used in hand dryers:
1) Brushless DC motors (expensive, good air speed)
2) Capacitor or induction AC motors (inexpensive, slow air speed)
3) Brushed Universal Motors (moderately expensive, good air speed)
4) Brushed DC motors - Rarely used in hand dryers these days
* Operational life of these motors will depend on their quality.
Universal Brushed Motors
These motors are called universal motors as they can work on AC as well as DC voltage. As you might have guessed, the brushed universal motors are most widely used motors in hand dryers as they provide best of both the worlds - good air speeds and cost efficiency. Below are some pictures of good quality brushed motors. These motors use special type of steel for stampings and construction, has UL certification which guarantees quality and safety as they are tested by an independent laboratory, thermal cut-off device to prevent overheating and big carbon brushes (minimum 1 inch in length).
The through flow vacuum brushed motor are usually used in vacuum cleaners but they have found application in high speed hand dryers. The traditional carbon brushed motor are also widely used. The through flow vacuum motors have RPM in excess of 20,000 RPM and the brushed motors have RPM in the range of 8000-15000 RPM.
Brushless DC (BLDC) motors
As the name suggests, these motors do not have carbon brushes for commutation. They use hall effect sensors and electronics for commutation. This motor is accompanied by a control PCB as shown in the picture below. The speed in these motors is not limited by friction of the carbon brushes and can be switched even thousands of times per second to provide high RPM which is not possible with other motors. This motor is also known by other names like digital motor or switched reluctance motor but they have the same working principle.
The reason for the high costs of a good quality BLDC motor is mainly due to use of powerful rare earth permanent magnets and lots of electronics for switching the motor. If the quality and design of the motor control circuit is not good, there can be exceptionally high failure rates and replacing them is very expensive. Also the voltages on some of the big capacitors on the control circuits can be in excess of 350V. Hence if they are not properly handled, it can lead to electric shock which could be fatal. So unless you are buying these hand dryers from a company which can ensure good quality of BLDC motors, it is better to avoid hand dryers with BLDC motors and go for brushed hand dryer motors instead. This will reduce initial cost of hand dryers by at least 30-40% and vastly reduce future maintenance overheads without much sacrifice in performance or user experience. Having a drying cycle time of 12 seconds or 15 seconds is a non-issue.
If you see a motor as shown in the picture below in a hand dryer, it is recommended not to buy such a hand dryer. Many cheap imported hand dryers in price range Rs 2000-Rs 6000 use these motors. These motors are usually used in toys and are not suitable for heavy duty operation. Not that these motors are bad, but they are not suitable for use in hand dryers. Many importers are not aware of the technical details and they want to import and sell the cheapest product available which are a safety hazard. Customers cant be expected to know such minute technical details of the products they buy. Lack of mandatory product quality certifications like UL and ISI for hand dryers in India allow such products to be sold causing problems for consumers and unnecessary competition for good quality hand dryer manufacturers.
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