Eaton DS7 Series, Manual

Page: 32 / 240

1 Device series DS7
1.14 Function
28
DS7 Soft starter 09/16 MN03901001Z-EN www.eaton.com
The mechanical apparatus of a drive unit controlled with a DS7 soft starter
are therefore accelerated very smoothly. This has a positive effect on the
lifespan, operating behavior and operating processes, and prevents any
adverse effects such as
• Impacting of cog edges in the gearbox
• Pressure surge in pipe systems,
• Slipping of V belts or
• Jitter with conveyor systems.
The generalized phase control of the supply voltage is implemented on the
DS7 soft starter by means of anti-parallel thyristors which are bridged for
continuous operation by so-called bypass contacts (TOR signal) after a time
controlled voltage change (t-Start) has elapsed.
The transition resistance of these bypass contacts is considerably lower than
the transition resistance of the power semiconductors. This reduces the heat
dissipation in the soft starter and extends the lifespan of the power
semiconductors.
Figure 13: Generalized phase control of the supply voltage
U
LN
= mains supply voltage
U-Start = start voltage
t-Start = Ramp time of the voltage change at start
TOR (Top of Ramp) = Signals the end of the set “t-Start” ramp time
(output voltage U
2
= mains supply voltage U
LN
).
Afterwards the internal bypass contacts are closed.
TOR
U
LN
t
U-Start
t-Start