Page 10 - Industrial Technology EXTRA 15th March 2021

This is now a locked rotor situation and the motor KEB Shredder VFDs can develop more torque compared to
will draw an extremely high current until the system line start motors, which allows the motor to ride through
is shut down or faults. It is likely that the shredder extreme loading conditions rather than stalling.
jam needs to be manually cleared, which requires
human intervention in the process and downtime. while sealing it from outside contamination. In this
In extreme loading (300% of rated torque), arrangement, the sensitive power electronics can be
KEB’s ASCL motor control drops the output sealed inside the enclosure while the air or water
frequency while keeping the full voltage to the flow is external. In cases where a customer does not
motor. This results in an over-magnetised motor that want to use the push-through design, KEB can offer
is capable of reaching much more torque than that alternative options.
of a line fed motor. This operation will increase
motor heating and is intended to temporarily ride Energy cost savings
through an impending jam condition. This results in Over a lifetime of operation, the energy costs required
the motor providing extra torque and clears the to operate these recycling machines are often more
material without needing to shut down. than the investment cost of the machine itself. This
energy cost calculation is easily made if you know the
Contamination issues size of the motor, duty cycles, and estimated lifetime
Another challenge that companies face in these service. It is possible to utilise energy-efficient
types of applications is the amount of components and VFDs that save energy.
contamination that can enter the electrical KEB’s technology enables energy savings in a
enclosure of the machine. Depending on the couple of different ways. First, KEB VFDs can run
process, it is possible that conductive metal high-torque PM motors, which are inherently more
shavings and oil are released into the air as the efficient than induction motors. In addition, these
material is being processed. Ensuring these high torque motors do not have mechanical gearing,
contaminants are not able to get into the electrical which also has mechanical losses. Second, KEB
components of the machine is critical. drives have the ability to measure ‘utilisation’ or the
KEB’s drives feature a number of heat sink current output as a percentage of its rated capacity.
options that will help protect the drives from these When under-utilised, the drive can signal to a PLC
particles. Several VFD heatsink options include the to increase the federate of material.
ability to push the heatsink outside of the panel www.keb.co.uk

March 2021 • INDUSTRIAL TECHNOLOGY EXTRA • p10