Red-lion MDC User Manual download pdf (Page 25)

Phase

The positive (+) phase of an output indicates that when the alarm becomes

active, the output turns on. When the output is reset it is turned off.

The negative (-) phase of an output indicates that when the alarm becomes

active, the output turns off. The reset condition of the output is the on state.

Boundary or Latched

An alarm programmed for Boundary Output becomes active as determined

by the alarm type (High, Low, Deviation, or Zero Speed). The output stays

active as long as this alarm trigger condition exists, after which the output

returns to its inactive state. A maintained reset on a User Input programmed

for Reset Alarm causes the alarm to stay in its inactive state at all times (see

Program User Menu).

An alarm programmed for Latched Output becomes active as determined

by the alarm type (High, Low, Deviation, or Zero Speed). The output stays

active until it is manually reset by a User Input selected for that function. A

momentary reset causes the output to return to its inactive state provided that

the condition causing the alarm no longer exists. A maintained reset on a User

Input programmed for Reset Alarm causes the alarm to stay in its inactive

state at all times (see Program User Menu).

Normal or Fast Update

The Normal update for the alarm outputs is once each second. This is the

same as the Speed or Ratio display update. The calculation to check for the

alarm condition is made from an average value of feedback measurements

taken over a 1 second period.

The Fast alarm update occurs at an interval less than or equal to 40 msec.

The calculation to check for the alarm condition is made from a single

feedback and/or lead frequency measurement. Since no average is made,

peaks caused by pulse encoder non-linearity (such as differences in the

spacing of teeth on a gear or an unbalanced shaft) can cause the alarm to

trigger early. THE FAST UPDATE SHOULD ONLY BE USED WHEN

FAST RESPONSE IS NECESSARY.

Stop Enabled or Disabled

This is an option that pertains only to the Low alarm and Deviation alarm. It

refers to the alarm function when the MDC is in STOP mode or ramping to or

from STOP mode. When the alarm is Stop Enabled, the alarm functions

normally in stop mode. A low alarm would always be on since zero speed is

always less than or equal to the speed setpoint.

When the alarm is programmed to be Stop Disabled, the alarm is always

inactive in stop mode and when ramping to or from stop mode. The alarm can

only become active after the speed setpoint value has been attained in Master

Mode, or when the ramp up to the setpoint ratio is complete in Follower Mode.

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Red-lion MDC User Manual Page 25