Omron K8AK-VS User manual
1
Single-phase Voltage Relay
K8AK-VS
Ideal for voltage monitoring for
industrial facilities and equipment.
• Monitor for overvoltages or undervoltages.
• Manual resetting and automatically resetting supported by one
Relay.
• One SPDT output relay, 5 A at 250 VAC (resistive load).
• Output relay can be switched between normally open and
normally closed.
• Process control signal (0 to 10 V) and current splitter input
supported.
• Output status can be monitored using LED indicator.
• Input frequency of 40 to 500 Hz supported.
• Inputs are isolated from the power supply.
Ordering Information
List of Models
Ratings and Specifications
Input Range
* The range is selected using connected terminals.
Refer to Safety Precautions for the K8AK Series on page 86.
Refer to page 30 for commonly asked questions.
For the most recent information on models that have been certified for
safety standards, refer to your OMRON website.
Setting range Control power supply
voltage Model
1 to 10 V AC/DC
3 to 30 V AC/DC
15 to 150 V AC/DC
24 VAC/DC K8AK-VS2 24 VAC/DC
100 to 240 VAC K8AK-VS2 100-240 VAC
20 to 200 V AC/DC
30 to 300 V AC/DC
60 to 600 V AC/DC
24 VAC/DC K8AK-VS3 24 VAC/DC
100 to 240 VAC K8AK-VS3 100-240 VAC
Model Range* Connection terminal Setting range Input impedance Overload capacity
K8AK-VS2
0 to 10 V AC/DC V1-COM 1 to 10 V AC/DC,
3 to 30 V AC/DC,
15 to 150 V AC/DC
Approx. 120 kΩ
Continuous input at
115% of maximum input
10 s at 125%
(up to 600 VAC)
0 to 30 V AC/DC V2-COM Approx. 320 kΩ
0 to 150 V AC/DC V3-COM Approx. 1.6 MΩ
K8AK-VS3
0 to 200 V AC/DC V1-COM 20 to 200 V AC/DC,
30 to 300 V AC/DC,
60 to 600 V AC/DC
Approx. 1.2 MΩ
0 to 300 V AC/DC V2-COM Approx. 1.7 MΩ
0 to 600 V AC/DC V3-COM Approx. 3.1 MΩ
K8AK-VS
2
Ratings
Power supply
voltage Isolated power supply 24 VAC/DC
100 to 240 VAC
Power consumption 24 VAC/DC: 2.0 VA/1.1 W max.
100 to 240 VAC: 4.6 VA max.
Operating value setting range (SV)
10% to 100% of maximum setting range
K8AK-VS2: 1 to 10 V AC/DC
3 to 30 V AC/DC
15 to 150 V AC/DC
K8AK-VS3: 20 to 200 V AC/DC
30 to 300 V AC/DC
60 to 600 V AC/DC
Operating value 100% operation at set value
Reset value setting range (HYS.) 5% to 50% of operating value
Reset method Manual reset/automatic reset (switchable)
Note: Manual reset: Turn OFF power supply for 1 s or longer.
Operating time setting range (T) 0.1 to 30 s
Power ON lock time (LOCK) 1 s or 5 s (Switched using DIP switch.)
Indicators Power (PWR): Green, Relay output (RY): Yellow, Alarm outputs (ALM): Red
Input impedance Refer to Input Range on previous page.
Output relays One SPDT relay (NO/NC switched using DIP switch.)
Output relay ratings
Rated load
Resistive load
5 A at 250 VAC
5 A at 30 VDC
Maximum contact voltage: 250 VAC or 30 VDC
Max. switching current: 5 A
Maximum switching capacity: 1,250 VA, 150 W
Mechanical life: 10 million operations min.
Electrical life: 5 A at 250 VAC or 30 VDC: 50,000 operations
3 A at 250 VAC or 30 VDC: 100,000 operations
Ambient operating temperature −20 to 60°C (with no condensation or icing)
Storage temperature −25 to 65°C (with no condensation or icing)
Ambient operating humidity 25% to 85% (with no condensation)
Storage humidity 25% to 85% (with no condensation)
Altitude 2,000 m max.
Terminal screw tightening torque 0.49 N·m
Terminal wiring method
Recommended wire
Solid wire: 2.5 mm2
Twisted wires: AWG16, AWG18
Note: 1. Ferrules with insulating sleeves must be used with twisted wires.
2. Two wires can be twisted together.
Recommended ferrules
Al 1,5-8BK (for AWG16) manufactured by Phoenix Contact
Al 1-8RD (for AWG18) manufactured by Phoenix Contact
Al 0,75-8GY (for AWG18) manufactured by Phoenix Contact
Case color N1.5
Case material PC and ABS
Weight Approx. 150 g
Mounting Mounts to DIN Track.
Dimensions 22.5 × 90 × 100 mm (W×H×D)
K8AK-VS
3
Specifications
Allowable operating voltage range 85% to 110% of rated power supply voltage
Allowable operating frequency range 50/60 Hz ±5 Hz
Input frequency 40 to 500 Hz
Overload capacity Continuous input at 115% of maximum input, 10 s at 125% (up to 600 VAC).
Repeat accuracy Operating value ±0.5% full scale (at 25°C and 65% humidity, rated power supply voltage, DC or 50/60 Hz sine
wave input)
Operating time ±50 ms (at 25°C and 65% humidity, rated power supply voltage)
Applicable stan-
dards
Conforming standards EN60947-5-1
Installation environment (pollution level 2, installation category III)
EMC EN60947-5-1
Safety standards UL 508 (Recognition), Korean Radio Waves Act (Act 10564),
CSA: CAN/CSA C22.2 No.14, CCC: GB14048.5
Insulation resistance
20 MΩ min.
Between external terminals and case
Between power supply terminals and input terminals
Between power supply terminals and output terminals
Between input terminals and output terminals
Dielectric strength
2,000 VAC for one minute
Between external terminals and case
Between power supply terminals and input terminals
Between power supply terminals and output terminals
Between input terminals and output terminals
Noise immunity 1,500 V power supply terminal common/normal mode
Square-wave noise of ±1 μs/100 ns pulse width with 1-ns rise time
Vibration resistance Frequency: 10 to 55 Hz, acceleration 50 m/s2
10 sweeps of 5 min each in X,Y, and Z directions
Shock resistance 150 m/s2 3 times each in 6 directions along 3 axes. Or 100 m/s2 for relay contacts.
Degree of protection Terminals: IP20
K8AK-VS
4
Connections
Wiring Diagram
●Overvoltage Operation Diagram
(Output Relay Drive Method: Normally Closed)
DIP switch setting: SW3 ON.
Note: The power ON lock prevents unnecessary alarms from being
generated during the instable period when the power is first
turned on. There is no relay output during timer operation.
●Undervoltage Operation Diagram
(Output Relay Drive Method: Normally Open)
DIP switch setting: SW3 OFF.
Note: The power ON lock prevents unnecessary alarms from being
generated during the instable period when the power is first
turned on. There is no relay output during timer operation.
Note: There is no polarity when a DC current input is used.
T1
T
Set value
Input
Power supply
voltage
Relay 11-14
Relay 11-12
Alarm indicator
T: Operating time (0.1 to 30 s)
T1: Startup lock time (1 or 5 s)
Lit
Flashing
Hysteresis
(−5% to 50% of operating value)
Lit
Flashing
T1 T1: Power ON lock (1 or 5 s)
TT: Operating time (0.1 to 30 s)
Hysteresis
(5% to 50% of operating value)
Power supply
voltage
Relay 11-14
Relay 11-12
Set value
Alarm indicator
Input
Load
Power supply
voltage
Voltage input
Signal output
14
12
A1
A2
V1
V2
V3
11
Relay
signal
output
C (COM)
Single-phase power
K8AK-VS
5
Nomenclature
Front ●Indicators
●Setting Knobs
Note: 1. Use either a solid wire of 2.5 mm2 maximum or a ferrule with
insulating sleeve for the terminal connection.
The length of the exposed current-carrying part inserted into
the terminal must be 8 mm or less to maintain dielectric
strength after connection.
Recommended ferrules
Phoenix Contact
•Al 1,5-8BK (for AWG16)
•Al 1-8RD (for AWG18)
•Al 0,75-8GY (for AWG18)
2. Tightening torque: 0.49 N·m
Power indicator
Relay status indicator
Voltage knob (SV)
Hysteresis knob (HYS.)
Operating time knob (T)
Alarm indicator
Terminal block
(See notes 1 and 2.)
Terminal block
(See notes 1 and 2.)
Item Meaning
Power indicator
(PWR: Green) Lit when power is being supplied.
Relay status indicator
(RY: Yellow) Lit when relay is operating
Alarm indicator
(ALM: Red)
Lit when there is an overvoltage or under-
voltage.
The indicator flashes to indicate the error
status after the input has exceeded the set
value while the operating time is being
clocked.
Item Usage
Voltage knob (SV) Used to set the voltage to 10% to 100% of
maximum setting range.
Hysteresis knob
(HYS.)
Used to set the rest value to 5% to 50% of
the operating value.
Operating time knob
(T) Used to set the operating time to 0.1 to 30 s.
For 2.5 mm2 or
smaller solid wires For ferrules with
an insulation sleeve.
8 mm max. 8 mm max.
K8AK-VS
6
Operation and Setting Methods
●Setting Ranges and Wiring Connections
●Connections
1. Input
Connect the input between terminals V1-COM, V2-COM, or V3-COM, depending on the input
voltage.
Malfunctions may occur if the input is connected to unused terminals and the Unit will not operate
correctly.
2. Power Supply
Connect the power supply to terminals A1 and A2.
3. Outputs
SPDT relays are output to terminals 11, 12, and 14.
Note: Use the recommended ferrules if using twisted wires.
●DIP Switch Settings
The power ON lock time, resetting method, relay drive method, and operating mode are set using the DIP switch located on the bottom of the Unit.
Model Setting range Wiring connection
K8AK-VS2
1 to 10 V AC/DC V1-COM
3 to 30 V AC/DC V2-COM
15 to 150 V AC/DC V3-COM
K8AK-VS3
20 to 200 V AC/DC V1-COM
30 to 300 V AC/DC V2-COM
60 to 600 V AC/DC V3-COM
Load
Power supply
voltage
Voltage input
Signal output
14
12
A1
A2
V1
V2
V3
11
Relay
signal
output
C (COM)
Single-phase power
DIP switch pins
SW3
ON
OFF
SW2
SW1
SW4
DIP Switch Functions
Note: All pins are set to OFF at the factory.
Pin
OFF ● ↑
ON ❍ ↓
Power ON
lock time
1 s ●--- --- ---
5 s ❍--- --- ---
Resetting
method
Manual reset --- ●--- ---
Automatic reset --- ❍--- ---
Relay drive
method
Normally open --- --- ●---
Normally closed --- --- ❍---
Operating
mode
Overvoltage --- --- --- ●
Undervoltage --- --- --- ❍
1
OFF
ON
2
3
4
K8AK-VS
7
●Setting Method
1. Setting Voltage
The voltage knob (SV) is used to set the voltage.
The voltage can be set to 10% to 100% of the maximum
setting range
.
Turn the knob while there is an input to the input terminals until the alarm indicator flashes (when the set value and the input have reached the
same level.)
Use this as a guide to set the voltage.
The maximum
setting range
will differ depending on the model and the input terminal.
Example: K8AK-VS3 Using Input Terminal V3-COM
The maximum
setting range
will be 600 VAC/VDC and the setting range will be 60 to 600 V.
2. Hysteresis
Hysteresis is set using the hysteresis knob (HYS.)
The setting range is 5 to 50% of the operating value.
Turn the knob while there is an input to the input terminals until the alarm indicator flashes (when the set value and the input have reached the same
level.)
Use this as a guide to set the hysteresis.
Example: Maximum Setting of 600 VAC/VDC, Voltage Set Value (SV) of 50%, and Overvoltage Operation
Operation will be at 300 V and resetting at 270 V when the hysteresis (HYS.) is set to 10%.
3. Operating Time
The operating time is set using the operating time knob (T).
The operating time can be set to between 0.1 and 30 s.
Turn the knob while there is an input to the input terminals until the alarm indicator flashes (when the set value and the input have reached the
same level.)
Use this as a guide to set the operating time.
If the input voltage exceeds (or drops lower than) the voltage set value, the alarm indicator will start flashing for the set period and then stay lit.
Dimensions (Unit: mm)
Single-phase Voltage Relays
Optional Parts for DIN Track Mounting
22.5
90
100
72 5
K8AK-VS2
K8AK-VS3
*Dimensions in parentheses are for the PFP-50N.
4.5
15 25 25
10 10
1,000 (500)*
25 25
15 (5)*
35
±0.3
7.3
±0.15
27
±0.15
1
●DIN Tracks
PFP-100N
PFP-50N
K8AK-VS
8
Checking Operation
Overvoltages
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.
Undervoltage
Gradually decrease the input from 120% of the set value and
check the operation using the same method as for
overvoltage.
Example: Overvoltage Operating Mode and an Operating Time of 5 s
Note: K8AK-VS@ output relays are normally operative.
Connection Diagram
How to Measure the Operating Time
Overvoltage
Change the input suddenly from 0% to 120% of the set value
and measure the time until the Unit operates.
Undervoltage
Change the input suddenly from 120% to 0% of the set value
and measure the time until the Unit operates.
Questions and Answers
Q
Q
Set value
Input voltage
Alarm indicator
Relay output
Flashing Lit
5 s
200 VAC
0 to 300 V
V
A1
A2
±C 200 V
Variable
autotransformer
Input terminals
Power supply
Cycle counter
Q
Q
9
Safety Precautions
Be sure to read the precautions for all models in the website at the following URL: http://www.ia.omron.com/.
Warning Indications
Meaning of Product Safety Symbols
Electrical shock may cause minor injury.
Do not touch terminals while electricity is being supplied.
There is a risk of minor electrical shock, fire, or device failure.
Do not allow any pieces of metal, conductors, or cutting chips
that occur during the installation process to enter the product.
Explosions may cause minor injuries. Do not use the product
in locations with inflammable or explosive gases.
There is a risk of minor electrical shock, fire, or device failure.
Do not disassemble, modify, repair, or touch the inside of the
product.
Loose screws may cause fires. Tighten terminal screws to the
specified torque of 0.49 to 0.59 N·m.
Use of excessive torque may damage the terminal screws.
Tighten terminal screws to the specified torque of 0.49 to 0.59
N·m.
If the setting does not match the element to be monitored, the
product may behave unexpectedly and damage the machine
or cause accidents. Set the K8AK-TH as described below.
•Adjust each set value on the K8AK-TH correctly for the
element that is to be monitored.
•Turn OFF the power to the K8AK-TH before you change
the switch settings on the side panel. The switch
settings made on the side panel take effect when the
power is turned ON.
If the K8AK-TH fails, the monitoring alarms 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 product regularly. To make the
product fail-safe, take alternative safety measures, such as the
installation of monitoring devices on a separate circuit.
Use of the product beyond its life may result in contact welding
or burning. Make sure to consider the actual operating
conditions and use the product within its rated load and
electrical life count. The life of the output relay varies
significantly with the switching capacity and switching
conditions.
1. Do not use or store the product in the following locations.
•Locations subject to water or oil
•Locations subject to direct radiant heat from heating equipment
•Outdoor locations or under direct sunlight
•Locations subject to dust or corrosive gases (particularly
sulfurizing gases, ammonia, etc.)
•Locations subject to rapid temperature changes
•Locations prone to icing and dew condensation
•Locations subject to excessive vibration or shock
•Locations subject to wind and rain
•Locations subject to static electricity and noise
•Habitats of insects or small animals
2. Use and store the product in a location where the ambient
temperature and humidity are within the specified ranges. If
applicable, provide forced cooling.
3. Mount the product in the correct direction.
4. Check terminal polarity when wiring and wire all connections
correctly. The power supply terminals do not have polarity.
5. Do not wire the input and output terminals incorrectly.
6. Make sure the power supply voltage and loads are within the
specifications and ratings for the product.
7. Make sure the type of the thermocouple matches the input type
that the K8AK-TH is designed for.
8. If you need to extend the length of the lead wires on the
thermocouple to use with the K8AK-TH, make sure to match the
type of thermocouple and always use compensating conductors.
9. To extend the lead wires on the platinum resistance thermometer
that is used with the K8AK-TH, use lead wires with a low
resistance (5 Ω or less per wire), and make the resistance equal
on all three lead wires.
10.Make sure the crimp terminals for wiring are of the specified size.
11.Do not connect anything to terminals that are not being used.
12.Use a power supply that will reach the rated voltage within 1
second after the power is turned ON.
13.After you turn ON the power, it takes 2 seconds for the outputs of
the K8AK-TH to stabilize. Take this time into account when you
design the control panel.
14.Allow at least 30 minutes for the K8AK-TH to warm up. During this
time, the temperature measurements will be incorrect.
15.Keep wiring separate from high voltages and power lines that
draw large currents.
Do not place product wiring in parallel with or in the same path as
high-voltage or high-current lines.
16.Do not install the product near equipment that generates high
frequencies or surges.
17.The product may cause incoming radio wave interference. Do not
use the product near radio wave receivers.
18.Install an external switch or circuit breaker and label it clearly so
that the operator can quickly turn OFF the power supply.
CAUTION
Indicates a potentially hazardous situation
which, if not avoided, may result in minor or
moderate injury or in property damage.
Precautions for Safe
Use
Supplementary comments on what to do or
avoid doing, to use the product safely.
Precautions for
Correct Use
Supplementary comments on what to do or
avoid doing, to prevent failure to operate,
malfunction, or undesirable effects on
product performance.
Used to warn of the risk of electric shock under
specific conditions.
Used for general prohibitions for which there is no
specific symbol.
Used to indicate prohibition when there is a risk of
minor injury from electrical shock or other source if
the product is disassembled.
Used for general mandatory action precautions for
which there is no specified symbol.
CAUTION
Precautions for Safe Use
10
19.When cleaning the product, do not use thinners or solvents. Use
commercial alcohol.
20.Make sure the power and output indicators operate correctly.
Depending on the application environment, the indicators and
other plastic parts may wear prematurely and become difficult to
see. Check and replace these parts regularly.
21.The terminal blocks may heat up to 65°C. Use care when
handling them.
22.Do not use the product if it is accidentally dropped. The internal
components may be damaged.
23.Be sure you understand the contents of this catalog and handle
the product according to the instructions provided.
24.Do not install the product in any way that would place a load on it.
25.When discarding the product, properly dispose of it as industrial
waste.
26.When using the product, remember that the power supply
terminals carry a high voltage.
27.The product must be handled only by trained electrician.
28.Prior to operation, check the wiring before you supply power to
the product.
29.Do not install the product immediately next to heat sources.
Observe the following operating
methods to prevent failure and
malfunction.
1. Use operating power, input power, and other power supplies and
converters with suitable capacities and rated outputs.
2. Allow only qualified personnel to manage or handle the product.
3. Use a precision screwdriver or similar tool to adjust the setting
knobs.
4. The distortion in the input waveform for the K8AK-AS, K8AK-AW,
K8AK-PH, K8AK-PA, K8AK-PM, or K8DS-PH must be 30% max.
If the input waveform is distorted beyond this level, it may cause
unnecessary operation.
Do not use the K8AK-VS or K8AK-VW in circuits with waveform
distortion. Error will be large due to waveform distortion.
5. Error will be large if the K8AK-AS, K8AK-AW, K8AK-VS, or K8AK-
VW is used for thyristor or inverter control.
The K8AK-PH, K8AK-PA, K8AK-PM, K8AK-PW, or K8DS-PH
cannot be used on the secondary side of an inverter. To use the
product on the load side of an inverter, install a noise filter on the
primary side of the inverter.
6. To reduce the error in the setting knob, always turn the setting
knob from the minimum setting toward the maximum setting.
7. Phase loss is detected for the K8AK-PA or K8AK-PM only when
the phase loss occurs between the input contacts and the power
supply. Phase loss is not detected on the load side.
8. Phase loss can be detected only from the input contacts to the
power supply side by the K8AK-PH, K8AK-PA, K8AK-PM, or
K8DS-PH. Phase loss cannot be detected from the input contacts
to the load side.
Mounting and Removing the K8AK
•Mounting to DIN Track
1. Catch the upper hook on the DIN Track.
2. Push the product onto the Track until the hooks lock into place.
•To remove the product, pull down on the bottom hook with a flat-
blade screwdriver and lift up on the product.
Mounting and Removing the K8DS
•The product may be mounted in any direction, but it must be
mounted securely and as level as possible.
•To mount the product to the DIN Track, hook it on the DIN Track at
(A) and then press in on the Unit in direction (B).
•To remove the product, insert a flat-blade screwdriver at (C) and
pull down the hook to release the Unit.
•Leave at least 30 mm of space between the product and other
devices to allow easy installation and removal.
Adjusting the Setting Knobs
•Use a screwdriver to adjust the setting knobs. The knobs have a
stopper that prevents them from turning beyond the full right or left
position. Do not force a knob beyond these points.
* (Not applicable to the K8AK-PH and K8DS-PH.)
Precautions for Correct Use
AB
PFP-100N (100 cm)
PFP-50N (50 cm)
Applicable DIN Tracks:
(A)
(B)
30 mm min.
(C)
Hook
Setting knob
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2
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