K8AB-AS Просмотр технического описания (PDF) - OMRON Corporation
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K8AB-AS Datasheet PDF : 10 Pages
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Questions and Answers
Q Checking Operation
Overcurrents
Gradually increase the input from 80% of the setting.
The input will equal the operating value when the input
exceeds the setting and the alarm indicator starts flashing.
Operation can be checked by the relay outputs that will
start after the operating time has passed.
Undercurrent
Gradually decrease the input from 120% of the setting and
check the operation using the same method as for
overcurrent.
Example: Overcurrent Operating Mode, Normally Open Relay Drive,
and an Operating Time of 5 s
Set value
Current input
Alarm indicator
Relay output
Flashing
Lit
5s
Connection Diagram
A
30 Ω 0 to 10 A Input terminals
100 VAC
400 W (two in parallel)
Power
A1
Variable autotransformer
supply
A2
Output
100 VAC
± C 100 V
Cycle counter
K8AB-AS
Q Operating Adjustment Knobs
Use a screwdriver to turn the knobs. There is a stopper to
prevent the knob from turning any further once it has been
turned completely to the left or right. Do not force the knob
past these limits.
Q Can a motor with a rated current of 5 A be monitored
using the K8AB?
Are there any application precautions?
The K8AB-AS1 and K8AB-AS2 cannot be used with motor
loads. Use the K8AB-AS3 in combination with the K8AC-
CT200L Current Transformer (CT). With motor loads, the
startup current and stall current will cause a current of many
times the rated current to flow. Refer to the following figure
for information on the motor startup current.
500%
100%
Several seconds to
several tens of seconds
Time from beginning of startup
For a motor with a rating of 5 A, the startup current will be
approximately 30 A. The startup current will exceed the
overload capacity (rating: 150% for 1 s) of the K8AB-AS1
and K8AB-AS2 and result in failure of the Relay.
To monitor the motor load, use the K8AB-AS3. (Overload
capacity: 120% of rating for continuous load, 200% of rating
for 30 s, and 600% of rating for 1 s).
The K8AB-AS3 has a large input range. Pass the conductors
multiple times through the special CT.
Q How to Measure the Operating Time
Overcurrent
Change the input suddenly from 0% to 120% of the set
value and measure the time until the Unit operates.
Undercurrent
Change the input suddenly from 120% to 0% of the set
value and measure the time until the Unit operates.
Q Monitoring Switch-mode Power Supplies
Switch-mode Power Supplies cannot be monitored. In
circuits with a capacitor input, including switch-mode power
supplies, the input capacitor recharge current flows in pulse
form as the load current. The K8AB-AS@ has a built-in filter
as a countermeasure against high frequencies and cannot
be used to remove pulse current.
To the K8AB-AS3
Primary-side conductor
K8AC-CT200L
Concept behind Passing Conductor through the CT When
Using the K8AB-AS3
Example: Monitoring Overload of a Motor with a Rated Current
of 5 A
K8AB settings:
Overcurrent detection, operating value setting: 25%, operating
time: 0.1 s
Startup lock timer: 0.1 to 30 s (Set the timer according to the
duration of the startup current.)
The setting range for the K8AB-AS3 is 10% to 100% of the rated
current (i.e., 10 to 100 A). Pass the conductors through the CT five
times so that at least 10 A of current flows. The input current to the
K8AB will be 25 A (i.e., 5 A x 5 loops).
If a startup current of six times the rated current is generated, it will
be 150 A (i.e., 25 A x 6). The overload capacity for the K8AB-AS3 is
200% of the rating for 30 s. The Relay will not fail even if the startup
current continues for 30 s, and it is possible to perform overload
detection.
ALL DIMENSIONS SHOWN ARE IN MILLIMETERS.
To convert millimeters into inches, multiply by 0.03937. To convert grams into ounces, multiply by 0.03527.
In the interest of product improvement, specifications are subject to change without notice.
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