IMR01M01-E5
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7.8 Automatic Power Frequency Detection and Power Frequency Monitoring Function
Automatic power frequency detection
The instrument automatically detects a power supply frequency (50 Hz or 60 Hz) when the power is turned on.
Detection range: 50 Hz = 45.0 to 54.9 Hz
60 Hz = 55.0 to 64.9 Hz
Power frequency monitoring function
This function monitors the power supply frequency and when it goes out of the detection range, the error message display
appears.
7.9 Heater Break Alarm Function
The heater break alarm monitors the current flowing through the load by a dedicated current transformer (CT).
The THV compares the measured value with the set values, and detects a fault in the heating or cooling circuit. In addition,
there are several types of heater break alarms depending on control methods and applications of these heater break alarms.
Read this chapter carefully to choose an suitable method and set an appropriate set value.
7.9.1 Common function for all types
Number of alarm delay times
To prevent producing a false alarm, the alarm function waits to produce an alarm status until the measured current by the CT
is in an alarm range for the preset number of consecutive sampling cycles. The parameter of the number of alarm delay times
is to change the number of consecutive sampling cycles by 5-cycle increment.
Heater break alarm 1: (5 cycles)
×
(Number of alarm delay times)
Heater break alarm 2: (5 cycles)
×
(Number of alarm delay times)
×
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7.9.2 Phase control
There are two alarm types (type 1 or type 2) available for phase control.
(1) Type 1
Type 1 can be used as follows by using two heater break alarm set values.
Heater break alarm 1 set value: The alarm can be output when a heater break occurs by setting the heater break alarm set
value.
Heater break alarm 2 set value: This alarm set value can be used as an auxiliary alarm.
For example, it can be used as a heater deterioration alarm if set to any value slightly
smaller than the heater break alarm set value to output the alarm before a heater break
occurs when the load current decreases due to heater deterioration, etc.
How alarm is activated
•
When heater current does not flow (Heater break, malfunction of the control device, etc.)
When the phase angle is equal to or more than 15% and the current transformer input value is equal to or less than the
heater break alarm set value for the preset number of consecutive sampling cycles, an alarm status is produced.
•
When heater current can not be turned off (Thyristor break-down or permanent damage)
When the current transformer input value is equal to or greater than the heater break alarm set value for the preset number
of consecutive sampling cycles, an alarm status is produced.
Type 1 cannot be used for the load of which resistance changes with time and/or temperature.
In addition, type 1 cannot be used for any power supply waveforms other than a sine waveform.
In order to prevent malfunctioning, it is so designed that no heater break alarm occurs at an phase angle of
less than 15 % (less than 15 % of maximum load current).
The alarm will be turned off when the current transformer input value goes in and stays at non-alarm range for five
consecutive cycles.
Related parameters
•
Maximum load current set value for alarm (P. 11)
•
Alarm output state selection (P. 13)
•
Number of alarm delay times (P. 12)
•
Heater break alarm 1 set value setting (P. 12)
•
Heater break alarm type (P. 12)
•
Heater break alarm 2 set value setting (P. 12)
•
Alarm output selection (P. 12)
•
Heater break alarm 2 used/unused (P. 12)
