Firing modes
7100A User Manual
3-4
3.3. SINGLE-CYCLE (code FC1)
‘
Burst mode
’ firing with a single firing or non-firing cycle is known as ‘
Single-cycle
’.
For example, with a setpoint of 50% (corresponding to a duty ratio
ηη
= 50%
) the modulation comprises
1 firing cycle and 1 non-firing cycle.
For duty ratios
ηη
< 50%
the
firing
time remains
unchanged
(1 cycle) and the non-firing time increases.
For duty ratios
ηη
> 50%
the
non-firing
time remains
unchanged
(1 cycle) and the firing time
increases.
3.4. ADVANCED SINGLE-CYCLE (code ASC)
In order to
reduce power fluctuations
during firing time, ‘
Advanced single-cycle
’ thyristor firing
mode uses:
• a whole number of
cycles
for firing, and
• a whole number of
half-cycles
for non-firing, and.
Important:
‘Advanced single-cycle’ firing mode is
only
available for
4S
or
6D
three-phase load
configuration.
For duty ratios
ηη
< 50%
:
- the thyristor firing time is
set to one cycle
- non-firing occurs for half-cycles.
For duty ratios
ηη
> 50%
:
- the non-firing time is
set to half a cycle
,
- firing occurs for whole cycles.
By using
half-cycles
for non-firing time, the modulation time is reduced compared with standard
‘Single-cycle’ mode, which is equivalent to burst mode with one cycle.
‘Advanced Single Cycle’ mode (Code ASC)
reduces flicker
on short wave infrared elements and is
thus less annoying on the eyes.
t
66.6% power
(F= 2 T
NF
)
T
M
T
F
T
NF
t
T
M
T
F
T
NF
•
Standard single-cycle
(T
F
or T
NF
= 1 cycle)
•
Advanced single-cycle
(T
NF
= 0.5 cycles: T
M
reduced)
66.6% power
(T
F
= 2 T
NF
)
Figure 3-4 Exemple of Single-cycle and Advanced sigle-cycle firing mode
71A3_Conduction_ENG_Iss2_1.qxp 1/09/06 16:15 Page 3-4
