Expert article

AC vs. DC overhead crane controls

Overhead crane with operator cab

For facilities seeking ways to reduce power consumption and long-term operating costs, a potential source of savings can be found by upgrading crane controls from DC power to AC power. 

 

By Scott McCauley,  Product Support Engineer   

 

Many older cranes operate on DC power because when those controls were built, DC was easier to supply and provided the power load necessary to drive large, robust pieces of equipment. But as technology advanced AC power also advanced. Today, a  conversion of overhead crane controls  to AC from DC pays off with a dramatic decrease in power consumption and attendant costs, sometimes by almost half. Here’s why: newer, more compact, lower HP motors draw a fraction of the amperage of their older, higher-HP counterparts. 

 

Make the switch to AC benefits you in the long run

Making the switch isn’t always as easy as it sounds. For many facilities, the major obstacle that stands in the way is a lack of AC power supply. Modernizing a facility to run on AC is a substantial investment on the front end, especially for steel mills, the biggest user of DC power today. But if a facility can make the switch, it’s worth it on the back end – not only for the potential long-term power savings, but also for the production downtime that can be avoided. 

If your organization depends on a DC powered crane, you should know that a malfunction could turn into a long-term problem. That’s because some DC technology is no longer available and replacement parts are becoming more difficult to obtain. Even worse, the fabrication of DC parts is expensive and requires long lead times—six to eight weeks, or even up to half a year. 

 

AC power allows for the addition of safety features and automation

On the other hand, AC power simplifies crane updates with the ability to add new safety and automation technology. And AC offers a wider range of parts and technology for crane modernizations, including automation, while offering better pricing. For example, with an AC-powered system, remote monitoring and programmable logic controls (PLC) can be added, as well as safety features such as collision avoidance. 

Another benefit of switching to AC power is longer crane life. The variable frequency drives of AC systems extend the life of cranes substantially, because there is less wear and tear on the motors. This is in contrast to DC contactors that allow an inrush of current, which results in similar stress on equipment as quickly as accelerating a car from zero to 60. 

A  crane modernization can convert overhead crane controls from DC power to AC power. For facilities that have an AC power feed, a modernization can take place gradually as production schedules and budgets allow.