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After a cold-start of a rectifier module, it will begin with nominal voltage (110, 220, 440V) until
the communication with the monitoring unit is established.
In the monitoring unit there is a parameter holding the level for the overvoltage protection
(HVSD). No matter the level of the requested setpoint, the output voltage of the module will be
limited to maximum 1% below existing HVSD level.
4.2.4
Current control
At normal operation the rectifier module will regulate according to the setpoint (current limit)
provided from the monitoring unit.
The current limit is also used as a tool for the functions temperature control, power control and
load sharing.
4.2.5
Temperature control
To protect the rectifier module from overheating, the current limit is lowered gradually as the
internal temperature gets close to a critical level. Should the temperature after all rise above the
critical level, the module will turn off and be kept turned off until the temperature has fallen to
a reasonable level. Meantime the cooling fans will run at full speed.
4.2.6
Output power control
At high output voltages, the output power will be limited to rated power by lowering the
current limit.
4.2.7
Fan speed control
In order to reduce the noise level to a minimum and to extend the lifetime of the fans, the fan
speed is regulated by the internal temperature of the module. The fan speed is continuously
monitored in order to provide an early warning if any of the three fans shows sign of being
worn out. Note that the fans by design are meant to last for the whole lifetime of the module.
Directly after start the cooling fans are working at full speed for about half a minute before
speed controlled by temperature begins.
At stop the cooling fans continues to run for about half a minute in order to cool off the
remaining heat.
4.2.8
Loadsharing
In the PRX3 up to 6 rectifiers can be working in parallel while sharing the load using so called
active loadsharing. The loadsharing is active in the range of about 10 – 90 % of the rated current.
During loadsharing, the first rectifier module acts as a master. The loadsharing will therefore
change from active to passive mode if that particular module is turned off or is out of order.
4.2.9
Overvoltage DC (HVSD)
In order to protect the site from hazardous overvoltage, an overvoltage protection called HVSD
(High Voltage Shut Down) is built into every rectifier module. The level is settled as a
parameter setting in the monitoring unit.
