11
11. Various Characteristics
11-1. Current Capacity and Calorific Value
When current flows in the thyristors, voltage (0.9-1.3 V) is generated across the terminals. The product (W) of this voltage across the terminals
and the current is Joule heat, which raises the temperature of the thyristor elements.
Full consideration needs to be given to radiation of heat and ventilation.
PAC 27 Internal Calorific Value
Current Capacity
20A
30A
45A
60A
80A
100A
Calorific value without fuse
23W
35W
54W
59W
79W
103W
Calorific value with fuse
25W
37W
58W
63W
85W
110W
11-2. Ambient Temperature and Load Current
The current rated for the PAC27 is at 50 ºC of ambient temperature. In case ambient temperature exceeds 50 ºC, the instrument should be used
with load current as illustrated below.
11-3. Control System and Output Waveform
11-4. Special Heater and Feedback Control
Type of heater
Feedback control system Additional function
Supercantal
Constant voltage c current limiting,
Constant power c current control, Constant current control
Pure metals
(platinum, molybdenum, tungsten, etc.)
Constant voltage c current limiting,
Constant power c current control, Constant current control
Carbon
Constant voltage control (+ current limiting), Constant power control
SiC (silicon carbide)
Constant voltage control (+ current limiting), Constant power control,
Constant current control
If rated current is exceeded when maximum output is produced during minimum heater resistance, the current limiting
function is required.
Phase control system
