44
If heater current consumption is 10.0 A or more:
Normal heater current – Heater burnout current
2.5 A
Heater burnout may not be detected if the difference is less than 2.5 A.
Example 1:
Using One 200-VAC, 1-kW Heater
Heater
1 kW
Control output
200 VAC
E5ZE-12
Normal heater current =
Heater burnout current = 0 A
Set value =
Normal current – burnout current = 5 – 0 = 5 A (
1 A)
= 2.5 A
= 5 A (
10 A)
1000
200
5 + 0
2
Example 2:
Using Three 200-VAC, 1-kW Heaters
Heater
1 kW x 3
Control output
200 VAC
E5ZE-12
Normal heater current =
Heater burnout current for 1 heater =
Set value =
Normal current – Burnout current = 15 – 10 = 5 A (
2.5 A)
= 12.5 A
3 = 15 A (
10 A)
1000
200
15 +10
2
1000
200
2 = 10 A
3-11 SSR Failure Detection
The Current Transformer (CT) can be used to measure SSR leakage current
and detect output short circuits. If an error is detected at any of the control points,
the HS alarm output will turn ON and the HS indicator will light. The CT can also
detect contact weld in relay.
Operating Conditions
•
Set the control point for which the HS alarm is to be used. The factory setting is
for the HS alarm to be disabled for all control points. The HS alarm is set by
executing the HB Alarm/HS Alarm Effective Control Point Setting (WU) com-
mand. If DeviceNet communications are being used, set the HS alarm with
FINS messages.
•
Set the SSR leakage current value. The setting range is between 0.0 and
50.0 A. The default is 0.5 A.
•
To check the CT current value, read the heater current and SSR leakage cur-
rent.
•
The SSR failure detection function operates when the control output is continu-
ously OFF for more than 100 ms.
•
The SSR leakage current varies depending on the load voltage. Set the SSR
failure detection current according to the heater power voltage that will actually
be used.
•
Turn ON the heater power either at the same time as or before turning ON the
power to the E5ZE. The HS alarm output will turn ON if the power to the E5ZE is
turned ON before turning ON the heater power.
Application Examples
SSR Failure Detection
Section 3-11
