Publication
9387900990
Revision
A
First Printing:
02/05
Revised:
08/05
Copyright
2005
FOR
INRUSH CURRENT
REDUCTION MODULE
ICRM-7, ICRM-15
INTRODUCTION
The Inrush Current Reduction Module (ICRM) prevents damage to a protected voltage regulator during power-up
by limiting inrush current to a safe level. Without inrush protection, the inrush current is limited only by the level of
the power source impedance. The lower the impedance, the greater the risk of damaging the regulator from
excessive inrush current. Devices with a pulse-width modulated (PWM) power stage are especially vulnerable to
high inrush current due to a large amount of capacitance inherent to the design. However, voltage regulators that
use SCR-type power stages do not require the protection of an ICRM since these regulators do not have a large
amount of capacitance in the power stage.
When a voltage regulator with a PWM power stage is energized, the ICRM limits the inrush current by adding a
high level of resistance in series with the voltage regulator power input. Once the inrush current subsides, the
series resistance diminishes quickly to allow nominal, steady-state current flow.
APPLICATION
Applications where a voltage regulator is powered by a permanent magnet generator (PMG), auxiliary winding, or
generator output (shunt fed) usually do not require the protection of an ICRM. These sources usually have a
higher source impedance which inherently minimizes inrush current. Also, these sources are typically connected
directly to the voltage regulator with no interposing relays, contactors, or switches. If this is the case, then no
inrush occurs since the source voltage ramps up to its rated value.
However, if rated or near rated voltage is applied to the voltage regulator, then some amount of inrush current is
expected and an ICRM should be considered. Typically, voltage regulators in these applications receive power
from a station service bus that is switched by a relay or contactor. Applications where a PWM type voltage
regulator is powered by a low-impedance source need an ICRM to minimize the amount of inrush current.
To summarize, if the voltage that powers the voltage regulator ramps up to nominal as the generator comes up to
rated speed, then an ICRM is not needed. If this is not the case, an ICRM should be used. If you are unsure
whether your application requires an ICRM, contact Basler Electric Technical Sales Support for assistance.
ICRM Versions
Two versions of the ICRM are available. Each version is uniquely suited to protect a specific family of Basler
Electric products. Table 1 lists each ICRM model, its part number, and the compatible products.
Table 1. ICRM Cross-Reference
Model Number
Part Number
Compatible Products
ICRM-7 9387900103
DECS-100
ICRM-15
9387900104
AVC63-12, AVC125-10, DECS-200
SPECIFICATIONS
The following electrical and physical specifications, type tests, and certifications apply to the ICRM.
CAUTION
If operating power is removed from an energized ICRM, a minimum interval of
five minutes should elapse before operating power is restored. This cool-down
interval allows the ICRM to regain its ability to limit inrush current.
