Sequence and reference explained – Yaskawa J7 Drive User Manual

Page 10

Sequence and Reference Explained

Sequence – refers to how the

rive is started, stopped, and told which direction to run.

When the sequence comes from the digital operator (local), the drive is started and stopped
using the “RUN” and “STOP” keys on the digital operator, and direction is given via the
“FWD/REV” key. Sequence can also come from the

rive’s control terminals (remote)

using either two-wire or three–wire control. The sequence inputs to the

rive do NOT

require any outside voltages to activate them. Instead, contact closures (either from
switches, relay contacts or open collector circuits) activate the sequence inputs. Other
sequence sources are available, consult the Technical Manual

or details.

Two-wire sequence – utilizes a “maintained” switch or relay contact. It is used on
applications where it is desirable to have the

rive restart on restoration of power. It

should not be used where safety of attending personnel might be threatened by a
restart. This method is generally restricted to unattended fans & pumps, or where
another controller is entrusted with the decision to restart. Direction is controlled by
maintaining either a forward run or a reverse run command.

Three-wire sequence – utilizes “momentary” buttons or switches. This control
scheme emulates the traditional 3-wire motor starter control. A momentary closure of
a normally open run switch latches the drive in the RUN
mode (STOP switch must be closed or the drive will not
accept the momentary RUN command). A momentary
opening of the normally closed STOP switch unlatches
RUN mode bringing the drive to a stop. The three-wire
sequence is used where it would be dangerous for the

rive to restart after a power outage. This method

requires an intentional restart, as the RUN command is
unlatched immediately on loss of power. Direction is
determined by another maintained contact closure (closed = reverse).

Reference - The frequency reference tells the

rive how fast to run the motor. There are

several source options for the frequency reference. First, the frequency reference can come
from the digital operator (local). Simply put, the motor speed can be entered into the
keypad. Second, the frequency reference can come from an analog signal (remote), such
as 0 to 10 Volts DC. When 0 Volts is applied to the

rive, the

rive will run at zero speed.

When 10V is applied to the

rive, it will run at full speed. Apply anything in between and the

rive will run at that corresponding frequency (2.5VDC = 25% speed = 15 Hz). Other

reference sources are available, consult the Technical Manual for details.

Local Control – is when the sequence and/or reference comes from the digital operator

Remote Control – is when the sequence and/or reference comes from the control
terminals.

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