Yaskawa VCD 723 - Manual (Page 114)

Glossary
108 Glossary
9/15/93
PAC task – The smallest unit which can be programmed in the PAC language.
Numerous types of PAC tasks are provided, each performing a specific, well
defined function. Each type of PAC task may be used numerous times in a PAC
design. Each PAC task is represented by a block on the PAC Diagram.
PAC task number – A unique number assigned by the PAC programmer to each
PAC task on the PAC Diagram. These numbers may be assigned in any order
and serve only as a means of identifying unique sources of information in the
PAC program. The system will support up to 32,767 PAC tasks with the
allowable task numbers being 1 to 32767.
Passive Hub – A central component in LAN star networks that splits the
network signal. Data integrity is ensured over a distance of 100 feet for a 4-port
Passive Hub.
PCB – Printed Circuit Board.
PCDU – Portable Control/Display Unit. A device which can plug into a drive or
an RDC, via a cable with a modular connector (similar to a telephone cord), that
has two lines of 16 character alphanumeric display and a 30 key keyboard. It
allows the viewing and setting of variables.
PCU – Power Conversion Unit. The power conversion unit refers to the
hardware and software associated with the power conversion from the AC lines
to the motor. Specifically, it refers to the hardware and software associated with
the PCU microprocessor as well as the power related components. The PCU is
responsible only for the power conversion process, not determination of how
much power should be converted (which is a function of the DCU).
Per-unit value – A per-unit value is a method of representing a quantity where
the value 1.0 represents the “Rated” value for that quantity. Whereas the
“Rated” value is generally a dimensioned value, the Per-Unit value is a
dimensionless quantity.
Power cube – The MicroTrac DSD chassis and all components mounted on or
inside it. A power cube alone cannot operate a motor; auxiliary items such as
isolation transformer, input circuit breaker, control power transformer and motor
loop contactor are needed to make up a complete MicroTrac DSD drive.
Queue – A list consisting of values where each new value is entered at the end
of the list and values read from the list are taken from the beginning of the list.
In other words, a first-in first-out [FIFO] buffer.
“RAM” – Random Access Memory. Memory that can be written to as well as
read from. The data in this memory is lost when the power is lost.