Case Study

A 125 tonne crane using a 100kW motor is used to help service stone crushing equipment operating in a massive South African open cast mine that covers over 375km2. The crane is required when the stone crusher becomes blocked or requires maintenance. And with this crusher being a primary crusher, reliable performance in this is of paramount importance, especially under such demanding operating conditions

The 132kW Optidrive P2 specified for this application has exceeded all of the demanding performance requirements. With this variable frequency drive in place the crane was able to operate with supremely smooth speed control for guiding bearings back into place in the stone crushers. With clearances down to as little as 20mm when replacing these bearings and any damage being extremely costly to repair, precise control is an absolute necessity.

Optidrive P2 was able to achieve this high performance thanks to a revolutionary patented motor control strategy that delivers 200 per cent torque down to 0.0Hz. This allows unique open loop control without the need for any feedback device as used in many traditional closed loop applications. Only the motor name plate data is required to achieve optimum performance. The drive continuously and automatically determines and tracks the key motor characteristics required for vector control.

An Invertek Drives technical manager said: "The Optidrive P2 has now been established for several years as a market leading variable frequency drive for applications with power outputs up to 160KW. At the top of the list of competitive advantages offered by the Optidrive P2 is its outstanding torque performance. Optidrive P2 has proven time and time again to provide more torque at low speed than other competitors products."

He added: "Up to 200 per cent starting torque means the drive can carry out the most arduous applications without an expensive and fragile encoder. In addition, because the torque can be controlled or limited, the need for mechanical torque limiting devices is eliminated in many applications and substantial savings on often expensive maintenance costs can easily be achieved due to shock loading being completely eliminated."

The issue that is often overlooked is that the low cost, maintenance free electronics replace expensive, maintenance prone mechanical devices, providing significant cost and maintenance benefits.

Optidrive P2 can be commissioned using a range of communication tools, including Optitools Smart Stick, designed for use with smartphones and PCs.