The difference between ac & dc garage door opener units:
When it comes to ac motors and dc motors they both do the same job they turn electricity into mechanical power. But they are both very different they are constructed differently from each other and they also use different ways to control the electricity to the motor also. A.C. Stands for alternating current and d.C. Stands for direct current. D.C. Motors are usually found in appliances that are operated by a battery like a power drill or even a radio controlled car toy. A.C. Motors are built very tough and rugged and made to have long life expectancy with very little if any maintenance as a.C . Motors do need some maintenance to last long periods of time. The only way to control the speed on an AC motor is to control the amount of electricity that is flowing to it the more electricity the faster it will spin.
As for a dc motor you can have the max amount of voltage to the motor and then you would have to have some kind of trigger or dial to control the amount of electricity to the motor the easiest way to give an example of this is a variable speed drill the harder you pull on the trigger the faster the drill will spin or you can just press halfway and get a half speed. The reason for dc motors in garage door openers is because they are easier to control with all the new technology that is coming out with these garage door openers the way they are engineered now it is easier for the computer control board in the garage door opener to use all of the new features that they offer now like backup battery systems and automatic pressure and speed control. If a garage door opener needs to operate during a power outage and needs to use the backup battery to operate the motor then it is a lot easier with a dc motor as opposed to an a.C. Motor.
Another advantage to having a d.C. Motor engineered into a garage door opener is they are considerably smaller in size than an a.C. Motor. This allows the garage door manufacturers to either design a smaller motorhead or fit more components into the original motorhead box and get more features out of the garage door opener. If your garage door opener has a battery backup system for power outages then it most definitely will have a d.C .Motor one reason is because you cant fit a backup battery into a conventional motor head with a a.C. Motor because of its bulky size. And also in my 15 years on the job I have replaced far more dc motors and I have ac motors. Most dc motors used with brushes and these brushes are used to transfer electricity to the motor and the brushes are a big part of the maintenance to a dc motor because they have to be replaced every 5 to 10 years depending on how often you use the dc motor. Also I in the past few years they have engineered a dc motor that does not use brushes so it lasts as long as an ac motor and very low maintenance so the technology is getting better and better every day. It won’t be long before ac motors become obsolete in garage door openers in the future. When it comes to dc powered garage door openers I think the positives outweigh the negatives when it comes to engineering garage door openers.