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Revision 8.6
SECTION 2 : SYSTEM DESIGN
16
2.5.3.
Relay Card
This card contains the five relays for switching the external contactors and the power supply for these
relays.
2.5.4.
Phase Shifter Card
This card determines the trigger delay angle for the firing of the thyristors as well as circuitry for
disabling the unit in the event of incorrect phase rotation, severe phase imbalance or low supply
voltage. The 10 Volt control voltage is derived from the main supply voltage within this card.
The thyristor firing circuitry uses a phase locked loop control circuit and is therefore not sensitive to
incoming mains disturbances.
The thyristor trigger module incorporates a unique dynamic time/amplitude transient clipping circuit.
2.5.5.
Snubber Card
This card protects the thyristors from supply voltage transients.
Together with the metal oxide varistors (MOV’s) mounted on the thyristors, the Snubber network card
provides a high degree of protection.
NOTE
The Snubber card is not used on Thyromat
units bigger than 1000A, the Snubber network
is then installed across the Thyristors on the
stack.
2.5.6.
Control Panel
The control panel is the man machine interface (MMI) of the Thyromat unit.
It serves as a window for monitoring various motor variables such as stator currents, motor speed,
drive status, etc…
It is used to enter the user parameters which make the Thyromat specific to the application.
