4-89
Chapter 4. Functions
For models with VT (voltage transformer) input, voltage can be measured by the VT input. Also, the resistance of
the actuator (heater) connected to the output of the AO-C block can be calculated from the voltage measured using
VT input and the current measured using CT input.
z
Primary voltage and secondary voltage
The setting is valid if the AO-C block is in the A2, B2, A1, or B1 slot. Settings can be adjusted to match the VT input
transformer.
Item (bank)
Display
Description
Initial value
Primary voltage
(VT bank)
MENU > VT
Primary voltage
1.0000 to 500.00
200.00
Secondary voltage
(VT bank)
MENU > VT
Secondary voltage
1.0000 to 11.000
10.000
Handling Precautions
•
Make sure that the voltage does not exceed the allowable input voltage (AC
0 to 18 VRMS and 26 V peak max.) of the VT input. Exceeding the upper limit
could cause malfunction.
•
If the voltage exceeds the rated input high limit of the VT input, a VT input
error alarm will be generated. However, if the voltage is too large and the
malfunction occurs, the VT input error alarm will not be generated.
•
The VT input and resistance can be displayed on the monitor screen of the
loop number that was set to "Input value display loop definition (CT/VT input
display loop definition)" in the basic action bank.
•
The actuator resistance can be calculated using the following formula.
Resistance (Ω) = VT input value (V) ÷ CT input value (A)
•
The actuator resistance cannot be calculated if the voltage of the VT input is
less than 0.1 V or if the current of the CT input is less than 0.1 A. In this case,
the resistance is 0.00 Ω.
•
The actuator resistance can be calculated only when using a thyristor and
phase angle control.
The resistance cannot be calculated when using thy cycle control or
SSR.
4 - 15 VT (Voltage Transformer) Input
