JUMO 709040 TYA-110 thyristor power unit Operating Manual - Manual (Page 14)

2 Operating modes
14 Power units 02.06
2.2 Burst-firing operation, for resistive loads
In this mode of operation, the power is regulated by changing the number of
full-wave cycles of the supply line voltage which are switched on during each
control period. This method is used for purely resistive loads which have a
cold resistance that is roughly the same as the hot resistance.
Since switching only takes place at the zero-crossing points, this mode of
operation produces very little RF-interference.
The internal switch S20 can be used to adjust the duty cycle to suit the system
being controlled.
v Section 6.2 “Adjustment switches S1 — 21 and pin headers X503 / X504”
Cycle time S 20
Variable cycle time
The control unit uses the shortest available cycle time
(for fast control loops) 1
Fixed cycle time (
≈ 500ms)
Used for transformer loads, slow control loops
2