In today’s tech demonstration, Rick Hillmer
walks us through an application that actually arose from a customer need.
The customer has a belt and pulley system driving a crusher. They
need to know as easily as possible if the belt starts slipping in order to stop
the infeed motor to the crusher. Let’s take a look.
Our suggestion to solve this issue, was to add a
flag on the driven pulley shaft and a proximity sensor to detect one pulse per
revolution, a very coarse encoder. At 1200 rpm, this will give me 20
pulses per second, or 20hz input. Using
the Digital inputs on the ACS880 as a frequency input, I am able to detect and
scale that speed back up to actual RPM. In this demo, we actually
used the 6 spokes of the pulley to give me 120hz.
I cheated and scaled this 120hz input to equal
1900 rpms to give me some margin of error over the drive motor actual speed.
Then using Adaptive programming, with one
compare block, I
compare the feedback speed to the actual motor speed. If feedback speed
is less than motor speed, with my margin of error, I turn on relay output 2.
I am using a VFD to run this pulley, to simulate
belt slipping. As you can see, if my driven pulley slows down,
Relay output 2 comes on. This will be
used at the customer site to prevent any more product from being fed into an
already overloaded system, preventing hours of downtime.
I can actually perform this same function with
an ACS380 micro drive, although I can’t get quite enough current to run a 500hp
Learn more about the ABB ACS880 Variable Frequency Drives.