Why We Do Things the DC Way
A long, long time ago there was a very heated, very public battle of wits between DC disciple Thomas Edison and his AC adversary, Nikola Tesla. Their feud was what started the age-old power struggle (literally) between direct current and alternating current, and while there has since been numerous accusations that the Father of DC’s character was less than savoury, there can be no doubt that this method of power distribution has made the world a better place (as has AC!).
In fact, DC has made such an incredible impact on the world that it has become a fundamental part of CENTSYS’s design philosophy. But why exactly has direct current become the preferred method of power distribution? Why is it that so many appliances nowadays has a built-in transformer and rectifier circuit to change the input AC voltage to low-voltage DC? And why do we at CENTSYS bank on it with our own products?
Well, we’ll tell you…
It’s More Cost-Effective to Implement
This is true for a number of reasons. Firstly, DC devices have only two conductors (namely positive and negative) versus the three (live, neutral and earth) needed for AC equipment. Since DC allows us to operate at much lower voltages, less insulation is typically needed which in turn leads to reduced costs.
Also worth noting is that DC circuits are generally less complex and require less components and yet they provide superior motor control to AC (another benefit – especially from an access automation point of view where one can accurately adjust running speeds for enhanced safety and security requirements).
Reliability and Autonomy
This point is probably a bit hackneyed, but we all know that it’s true. When the Dark Knight does rise (we’re talking about power failures, in case that metaphor was a bit obscure), it’s important that your appliances carry on working despite the sudden loss of mains power.
Direct current makes this a possibility. You’ve all heard the term “battery backup” being used – now, the battery being a staple of DC power distribution – is what allows your gate motor to dutifully carry on serving you even during lengthy power failures. AC machines can still be outfitted with backup, but it requires costly additions such as DC converters. Backup is native to DC machines.
This point ties in very closely with the one above. Since DC operators gives you a mechanism to fairly easily decouple yourself from the main utility grid using solar power and other energy generators, you are effectively putting another level of protection between you and possible lightning damage.
Higher Starting Torque
While it’s true that AC motors produce higher running torque, think in terms of gate automation. What is more important: setting your gate in motion or keeping it that way? If you guessed “setting your gate in motion”, congratulations! You know your stuff.
DC motors produce superior starting thrust, which is what you need especially if your gate is slightly on the heavy side. Once it’s on the move keeping it that way is, well, automatic.
Improved Collision Detection
DC machines have been found to be more sensitive than their AC counterparts from a collision detection perspective. This is an important feature to have in your automated system, especially if you have kiddies or pets around.
In a nutshell, the load speed profile of DC motors is such that they tend to slow down when obstructed whereas AC motors are synchronous and only slow down when they literally stall against the load. It is quite simply easier to electronically detect a DC motor hitting an obstruction which in turn allows us to apply more sensitive anti-crushing protection.
It Allows Us to Operate in the Safe Zone
Edison once notoriously performed a public demonstration involving an elephant to show the dangers of alternating current, but that’s kind of a cheap shot (not to mention utterly inhumane) and we won’t resort to that here. Besides, at high voltages DC can be much more dangerous than AC.
The fact is, the DC we employ in our gate motors is of the low-voltage variety (typically around 12-24V) which means that it is much, much safer than the AC alternative.
Please note that our aim is not to slate AC in any way. On the contrary, one of our most robust operators – the A10 – is an AC mean machine and offers myriad benefits such as a higher duty cycle and improved running torque that a DC unit might not be able to provide. Our goal is simply to provide you with some insight as to why DC is such an important part of our design philosophy.