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K8DT-AS

9

Checking Operation

Overcurrents
Gradually increase the input from 80% of the set value.
The input will equal the operating value when the input 
exceeds the set value 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.

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.

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 K8DT-AS

@

 has a built-in filter as a 

countermeasure against high frequencies and cannot be 
used to remove pulse current.

Can a motor with a rated current of 5 A be monitored 
using the K8DT?
Are there any application precautions?

The K8DT-AS1 and K8DT-AS2 cannot be used with motor 
loads. Use the K8DT-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.

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 K8DT-AS1 and 
K8DT-AS2 and result in failure of the Relay. 
To monitor the motor load, use the K8DT-AS3. (Overload 
capacity: 120% of rating for continuous load, 200% of rating 
for 30 s, and 600% of rating for 1 s).
The K8DT-AS3 has a large input range. Pass the conductors
multiple times through the special CT.

Concept behind Passing Conductor through the 
CT When Using the K8DT-AS3

Example: Monitoring Overload of a Motor with a Rated Current of 5 A

K8DT set value: 
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 K8DT-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 
K8DT 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 K8DT-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.

Questions and Answers

Q

Current input

Set value

Alarm indicator

Flashing

5s

Lit

Contact output or 

transistor output

A1

Output

Input terminals

Power

supply

A2

±

C

100 VAC

100 VAC

100 V

A

Cycle counter

0 to 10 A

30 

Ω

400 W (two in parallel)

Variable autotransformer

Example: Operating Mode = Overcurrent, Output Drive Mode = 
Normally Open, and Operating Time = 5 s

Connection Diagram

Q

Q

Q

Several seconds to 
several tens of seconds

Time from beginning of startup

100%

500%

Motor current (percentage of r

ated v

alue)

K8AC-CT200L

Primary-side conductor

To the K8DT-AS3

Содержание K8DT-AS Seriesl

Страница 1: ...K8DT AS2 Options Order Separately Front Cover Refer to Safety Precautions on page 10 Refer to page 9 for commonly asked questions For the most recent information on models that have been certified for...

Страница 2: ...DC Approx 5 Direct input Continuous input at 120 of maximum input 1 s at 150 100 mA AC DC I2 COM 10 to 100 mA AC DC Approx 1 Direct input 500 mA AC DC I3 COM 50 to 500 mA AC DC Approx 0 2 Direct input...

Страница 3: ...rules Applicable wire size 0 25 to 1 5 mm2 AWG24 to AWG16 Wire insertion force 8 N max for AWG20 wire Screwdriver insertion force 15 N max Wire stripping length 8 mm Ferrule length 8 mm Current capaci...

Страница 4: ...copper wires with a rating of 75 C or an equivalent rating Inside Inside 1 Current Input AS1 2 Output C Relay Output T Transistor Output 3 Power Supply Voltage A 100 to 240 VAC D 24 VAC DC No polarit...

Страница 5: ...ge Contacts 11 12 Set value Alarm indicator Lit Contacts 11 14 or transistor output Input Delay time 250 ms reference value Terminal block See note Terminal block See note Current knob SV Hysteresis k...

Страница 6: ...front of the Unit For the K8DT AS SW1 is not used Note Open the DIP switch cover to set the DIP switch Keep the DIP switch cover closed while the power supply to the Relay is ON Model Setting range I...

Страница 7: ...et Value SV of 50 and Overcurrent Operation Operation will be at 100 A and resetting at 90 A when the hysteresis HYS is set to 10 Operating Time The operating time is set using the operating time knob...

Страница 8: ...3 1 7 1 7 9 3 76 Two M5 screw holes or two 5 5 dia holes OMRON CT K8AC CT200L Mounting Hole Dimensions Note The OMRON Current Transformer CT is designed to be used with the K8DT AS3 Use terminals k an...

Страница 9: ...ely 30 A The startup current will exceed the overload capacity rating 150 for 1 s of the K8DT AS1 and K8DT AS2 and result in failure of the Relay To monitor the motor load use the K8DT AS3 Overload ca...

Страница 10: ...ails monitoring and alarm outputs may fail to operate This may result in physical damage to the facilities equipment or other devices that are connected to it To reduce this risk inspect the Relay reg...

Страница 11: ...pply power to the product 22 Do not install the product immediately next to heat sources 23 Perform periodic maintenance 24 Do not wire anything to the release holes 25 When you insert a flat blade sc...

Страница 12: ...rom the release hole Checking Connections After the insertion pull gently on the wire to make sure that it will not come off and the wire is securely fastened to the terminal block To prevent short ci...

Страница 13: ...re is basic insulation between the power supply terminals and input terminals There is basic insulation between the power supply terminals and output terminals There is basic insulation between the in...

Страница 14: ...MEMO 14...

Страница 15: ...CONNECTED WITH THE PRODUCTS WHETHER SUCH CLAIM IS BASED IN CONTRACT WARRANTY NEGLIGENCE OR STRICT LIABILITY Further in no event shall liability of Omron Companies exceed the individual price of the Pr...

Страница 16: ...IL 60169 U S A Tel 1 847 843 7900 Fax 1 847 843 7787 Regional Headquarters OMRON EUROPE B V Wegalaan 67 69 2132 JD Hoofddorp The Netherlands Tel 31 2356 81 300 Fax 31 2356 81 388 Contact www ia omron...

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