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K8AC-H
Heater Connection Methods and Current
Depending on the heater connection method, the current when an error occurs will be as shown in the following table. Refer to this table when
determining burnout alarm set values.
Single-phase
Delta
connection
Three-
Star
phase
connection
V
connection
Note: This is the current for when a 200-V, 1-kW heater is used for single-phase or three-phase operation.
Rate of Change for Currents with Parallel Heaters
The following table shows the current change ratios when multiple heaters of the same capacity are connected in parallel and one of the heater
elements burns out. Use this table for reference when making corrections.
If five single-phase heaters are connected in parallel, the current change when burnout occurs is 20% per heater.
For example, if the current for a single heater is low and the change ratio is very slight, it may not be detected. Therefore take into account the
detection accuracy for the total current when selecting the number of heaters to be connected in parallel.
Connection
I
Single-
n heaters
phase
I
Number of
heaters per
phase = n
Star
connection
I
Delta
connection
Number of heaters
per phase = n
Note: 1. The figures in the above table show the current change ratios when burnout occurs for one heater connected in parallel.
2. The numbers represent the current ratio after one heater burns out, with the current prior to the burnout (i.e., the normal current) taken
as 1.
3. In actual operation there may be effects from factors such as load (heater) imbalances, so conduct an actual test for confirmation before
making adjustments if the current change ratio between normal and abnormal operation is slight.
4. Consult with your OMRON representative if multiple heaters are used with different heater capacities.
10
Normal condition
5 A
200 V
1 kW
5 A
8.7 A
1 kW
200 V
8.7 A
200 V
1 kW
200 V
1 kW
8.7 A
(5 A × 3 )
2.9 A
1kW
200 V
2.9 A
200 V
1 kW
200 V
1 kW
2.9 A
1
(5 A ×
)
3
5 A
1 kW
200 V
8.7 A
200 V
200 V
1 kW
5 A
(5 A × 3 = 8.7 A)
With one heater
burned out,
With one heater
Current in burned-
burned out,
out phase
Current in other
phases
Current in lines
near burned-out
phase (Same as 2-
phase.)
Current in other
phases
200 V
7.5 A
7.5 A
3
(5 A × 3 ×
)
2
2.5 A
2.5 A
1
3
)
(5 A ×
×
3
2
2.5 A
2.5 A
1
(5 A ×
)
2
n=1
n=2
0.5
I is 0.
0.6
I is 0.
0.87
0.92
0.58
0.77
1
1
Abnormal condition
0 A
0 A
5 A
8.7 A
5 A
1
(5 A × 3 ×
)
3
2.5 A
2.5 A
1
3
(5 A ×
×
)
3
2
5 A
5 A
(5 A × 1)
n=3
n=4
0.67
0.75
0.75
0.82
0.95
0.96
0.84
0.88
1
1
n=5
0.8
0.86
0.97
0.91
1
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