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Operation
ATP ANALOGUE SIGNAL (‘Burst’ mode)
When an analogue signal (4 - 20 mA) is applied to the ATP input (or Digital
communication is used) the 7100S series unit operates in ‘Burst mode’.
‘Burst mode’ firing is a proportional cycle which delivers a series of complete half-cycles
to the load.
Thyristor firing and cut-off is synchronised with the supply and occurs at zero crossing.
Load
voltage
t
TNF
TF
TM
Figure 3-2 Thyristor firing in ‘Burst mode’
Thyristor firing in ‘Burst mode’ can be described by the firing time (TF) , non-firing time
(TNF) and modulation time (TM) where TM = TF + TNF
Firing in ‘Burst mode’ is defined by the Base Cycle Time (TB).
The base cycle time is equal to the firing time at 50% power.
The base time for 7100S units with an ATP input is:
TB = 0.3 s ± 20%
giving a modulation time of TM = 0.6 s ± 20%.
Modulation TM
period
5.0 s
4.0 s
3.0 s
2.0 s
(TF = TNF)
1.0 s
TB = 0.3 s
0.6 s
0
25%
50%
75%
100%
Output power
(analogue setpoint)
Figure 3-3 ‘Burst mode’ modulation period depending on analogue signal (ATP input)
7100S User Manual
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