5
SECTION ONE
Refer to the overall schematic in the Appendix.
It is not the intention of this manual to enter into a detailed description
of the unit's operation. Moreover, it is intended to provide the reader
with a general view of the unit's main assemblies. With this information,
the repair technician should have a better understanding of the unit's
operation and therefore aid in the troubleshooting process.
The VLT is divided primarily into three sections commonly referred to
as: logic, power, and interface.
The control card itself primarily makes up the logic section. The heart
of the control card is a microprocessor which controls and supervises
all functions of the unit's operation. In addition, a separate PROM
contains the parameter sets which characterize the unit and provide
the user with the definable data enabling the unit to be adjusted to
meet the customer's specific application. This definable data is then
stored in an EEPROM which provides security during power-down and
also allows flexibility for future changes as needed. A custom integrated
circuit generates the PWM waveform which is then sent on to the
interface board for distribution to the individual gate drive circuits.
DESCRIPTION OF
OPERATION
LOGIC SECTION
Also, part of the logic section is the keyboard/display
mounted on the control card. The keyboard provides
the interface between the digital logic and the human
programmer. The LCD (Liquid Crystal Display)
provides the operator/programmer with menu
selection, unit status and fault diagnostic information.
Programming is accomplished through the use of four
of the eight keys available on the keyboard. The
additional four keys provide Local Start, Stop, Forward/
Reverse and Jog.
A series of customer terminals are provided for the
input of remote commands such as: Run, Stop and
Speed Reference. Terminals are also provided to
supply outputs to peripheral devices for the purpose
of monitoring and control. Two programmable relay
outputs are also available to interface the unit with other
devices.
In addition, the control card is capable of
communicating via a serial link with outside devices
such as a personal computer or a programmable logic
controller.
The control card provides two voltages for use from
the customer terminal strip. The 24VDC is used
primarily to control functions such as: Start, Stop and
Forward/Reverse. The 24VDC is provided from a
separate section of the unit's power supply and is
delivered to the control card from the interface board
via the two conductor ribbon cable.
MICROPROCESSOR
ADRESS
DATA
RAM
EPROM
EEPROM
VVC
CONTROL
POWER
POWER
FEEDBACK
ANALOG
INPUTS
ANALOG
OUTPUTS
DIGITAL
INPUTS
DIGITAL
CHANNEL
2
1
1
1
D
A
D
A
KEYBOARD
DISPLAY
RELAY