Questions And Answers - Omron K8DT-PZ Series Manual

Questions and Answers

Checking Operation
Q
Overvoltage
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 because the Relay will operate
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 an
overvoltage.
Example: Monitoring Mode for Rated Voltage of 200 V and an Operating
Time Setting of 5 s
Operating set value
Input voltage
Alarm indicator
Contact output
or
Transistor output
Asymmetry
With the rated input voltage applied, gradually change one of
the phase-to-phase voltages. The Relay will operate when
the difference between the highest and lowest voltage
phases reaches or exceeds the asymmetry operating value.
Asymmetry operating value =
Rated input voltage × Asymmetry set value (%)
Example: Monitoring Mode for Rated Voltage of 200 V and an Operating
Time Setting of 5 s
L1
Input L2
L3
Alarm indicator
Contact output
or
Transistor output
T1: Power ON lock (1 or 5 s)
Connection Diagram 1
3-phase,
200 VAC
L1
L2
L3
3-phase variable autotransformer
Flashing Lit
5 s
Asymmetry operating voltage (set value)
Flashing
Lit
T: Operating time (0.1 to 30 s)
T
L1
V1
L2
V2 V3
L3
0 to 150 V
How to Measure the Operating Time
Q
Overvoltage
Change the input value quickly from 70% to 120% of the set
value and measure the time required for the Relay to operate.
Undervoltage
Change the input value quickly from 120% to 70% of the set
value and measure the time required for the Relay to operate.
Operating Time
Adjust the slide resistor so that the voltage applied to the
K8DT terminals is 120% of the set value for overvoltage
detection, 80% of the set value for undervoltage detection, or
equal to or greater than the asymmetry operating value when
the auxiliary relay in connection diagram 2 operates.
Close the switch and use a cycle counter to measure the
operating time.
Connection Diagram 2
3-phase, 200 VAC
L1
X/a
X
L2
L3
± C 200 V
Cycle counter
Checking the Phase Sequence and Phase Loss
Q
Operation
Phase Sequence
Switch the wiring, as shown by the dotted lines in connection
diagram 1, to reverse the phase sequence and check that the
K8DT operates.
Phase loss
Create a phase loss for any input phase and check that the
K8DT operates.
K8DT-PZ
L1
V1
L2
V2 V3
R1
X/b
L3
R2
R1: Sliding resistor, 200 Ω, 200 W
R2: 100 Ω, 400 W
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