The main drive in this web transport system is a
solid state variable speed DC drive allowing for
independent control of speed and torque of the
DC motor. Indpendently controlling speed and
torque is how web tension control is achieved in
these types of systems. The solid state variable
speed DC drive shown is referred to as a chassis
mount drive, operated electrically by 230V AC
single phase power. Control relays operate using
AC control voltage in response to machine
operator pushbutton and switch controls. Note
the snubbers also known as quench arcs on the
coil circuit of each control relay. They consist
of a resistor and capacitor network which is
designed to absorb voltage spikes when the coil
is de-engergized causing the magnetic flux field
around the coil to collapse. This prevents radio
frequency interference (RFI) in control
circuits, as well as protects the drive from
damage due to voltage spikes on the control
inputs. Note the unused F1, F2 dc motor field
terminals on the drive. This drive operates a
permanent magnet field (PM) type motor. The
drive system is built on a removable backpanel
that will be installed in an electrical
enclosure. All drive and control relay functions
are wired to the separately mounted terminal
strip for ease of user connections. Applications
of this type of system are found in textile,
wire and rope, plastic and rubber hose, film and
similar manufacturing operations. Simple to set
up and use, this system operated a high capacity
production process reliably for many continuous
hours during production runs.