Electric Chain Hoist – Consider VFD!
Hoist are commonly used with jib, gantry and workstation cranes. In the hoist world, hoists are either 3-Phase (230/460-3-60) or 1-Phase (115/230-1-60) and either single speed or dual speed. Some manufacturers accomplish dual speed with contactors or Variable Frequency Drives (VFD’s) with the ladder becoming more popular and contactors being phased out altogether. Which should a user consider?
In the mid-2000’s hoist manufacturers and VFD manufacturers found a way to work together on size and cost. This partnership resulted in R&D that produced VFD’s able to fit inside the control cover of a hoist and a price point that rivaled traditional contactor control. The advantage is a hoist that can be easily adjusted to an operators’ need or comfort level and less maintenance and repair on the hoists.
The VFD is a simple mechanism that varies the frequency to the motor, thus allowing for different speeds. These new VFD’s can be pre-set to factory low and high speeds or infinitely variable allowing the user to accelerate and decelerate the hoist (like a throttle). The ability to change the speed allows for critical positioning of the parts being lifted or a fast, empty hook speed to work quickly and efficiently.
Every application is different. Some users want to match the speeds of the hoist already in their facility. Some users prefer a very slow positioning speed (low speed) and a very fast production speed (high speed). Some prefer the difference between the speeds to be minimal and some prefer all speeds to be either slow or fast. The VFD allows the user to program all these scenarios.
The real value is in the maintenance. No longer does an end user need to replace contactors every ~100,000 starts or worry about a contactor failing during a critical lift. Motors are produced as single speed motors so the need for multiple windings is eliminated, thus reducing motor costs. Also, most VFD’s can now measure resistance (load) as well as identify when the hook is empty allowing for an even faster empty hook speed for faster production.
Finally, the best result is price. For less than the cost of traditional dual speed contactors (which have set speeds that are not adjustable), hoist VFD’s offer adjustable speed control for less money. Maintenance is less because the motor and electrical design is simpler and thus troubleshooting is easier.
There will be a day when hoist manufactures only manufacture hoists with VFD’s. The days of single speed and dual speed contactor hoists are coming to an end. After all, why would you want to buy a hoist (motor) that you can’t adjust the speed?