Within the field of electrical technology, the “contactor” has been for many years, the main actor of the motor starting systems , being the most widely used at the time for making effective load switching. However, under a scenario with cheaper and lower quality solutions, the correct use of this device is not completely clear. As a broad scope exists, it has not been limited or specialized to deliver the best switching solution in applications with higher requirements, such as seen in the Andean countries in mining operations at high altitude.
This post discusses the use of contactors in hoisting machinery according to IEC 60204-32, the international standard which defines the minimum safety requirements for load lifting machinery. This standard defines the layout of electrical systems, regulatory requirements for devices, installation recommendations and control systems of lifting.
According to IEC 60204-32 hoisting machines include cranes of all types, winches of all types, and storage and retrieval machinery, considering the following groups of machines:
- overhead travelling cranes;
- mobile cranes;
- tower cranes;
- slewing luffing cranes;
- gantry cranes;
- offshore cranes;
- floating cranes;
- winches of all types;
- hoists and accessories;
- loader cranes;
- cable cranes;
- load holding devices;
- storage and retrieval machines;
- monorail hoists;
- straddle carriers;
- rubber tyred gantry cranes (RTGs).
The standard defines the use of contactors for any lifting system, independent of its features and its installation site therefore specifies each of the requirements according to the different factors that influence the correct operation of the device by minimizing the risk of failure due to poor specification.
In part 2 of this post I will take a closer look at the requirements for selection of power contactors and environmental conditions that affects normal operation of these devices.