Alpha Technologies AMP24 HP - Manual (Page 68)

Doc. #: 0260011-J0 Rev B 66
6.4.4 Over Temperature Protection
Each rectifier module is protected against an excessive increase in temperature caused by a component
failure or a cooling airflow blockage. During over-temperature conditions, the rectifier limits the output
power and the output current. If the temperature continues to increase, a shutdown of the rectifier is
initiated. The rectifier restarts automatically when the temperature returns to a safe level.
6.4.5 Wide AC Range
A minor alarm is generated when the AC input voltage drops below its allowable limit. The rectifier output
power is reduced linearly between 187 Vac and 90 Vac. At 90 Vac, the unit delivers derated output power
that is more than 33% of the rated output power.
Below 90 Vac, the module shuts down and restarts only when the AC voltage is greater than 95 Vac.
The actualrestart voltage depends on the load current. A reduced load current may allow a restart input
voltage as low as 100 Vac.
For voltages above 277 Vac, the power factor and total harmonic distortion may be derated. Up to 312
Vac (320 Vac for the 1.8 rectifier), the rectifier is operational and will not suffer any damage.
6.4.6 AC Inrush/Transient Suppression
To prevent a surge on the AC input line, the inrush current of a rectifier module is limited to the full
load steady state line current. Modules are also protected from input lightning and transient surges in
accordance with IEEE/ANSI C62.41 Category B3 standards.
6.4.7 Soft Start
A soft start feature is used to eliminate an instantaneous demand on the AC power source. A soft start,
sometimes referred to as a “current walk-in”, works by gradually (up to five seconds) ramping up the
current limit from zero to the actual or defined customer setting. The rectifier output voltage is ramped
from the minimum voltage to the float voltage.
6.4.8 Start Delay
The rectifier modules are equipped with a delay timer to stagger-start a series of modules to prevent
excessive loading of generators upon start up. The built-in timer delays the switching on of the module by
an interval (up to 120 seconds), which is set in the CXC. A minimum one-second delay is preset to allow
the input capacitors to charge.
6.4.9 Current Limit/Short Circuit Protection
The current limit function determines the maximum output current limit of the rectifier module, regardless
of the output voltage or power. The maximum output current is limited to a constant value down to a short
circuit condition. Current limiting can be used to mate the rectifier output current ampacity to the needs of
the load and parallel battery to minimize excessive battery recharge currents.
The rectifier will sustain a short circuit at the output terminals indefinitely. The maximum short circuit
current will not exceed 105% of the rated full load current.