Emerson Epsilon Eb Series Reference Manual page 60

Shunt Monitoring Algorithm
E
E Series Only
N
The algorithm used for monitoring shunt utilization accurately determines the shunt
resistor capacity available under various operating conditions. The drive monitors the
amount of power being dissipated by the shunt and if the power dissipation exceeds the
allowable limit a Shunt Fault is generated. The allowable shunt capacity varies based on
the actual drive loading and ambient temperature.
The heat sink is designed with a certain amount of dissipation capability and the sum of
the heat generated by the drive bridge rectifier, power module and shunt resistor must be
less than this total capacity. For example, if the drive is operating near its continuous
current limit with a 40 ° C ambient, most of the heatsink capacity will be used to dissipate
the heat generated by the output power module and bridge rectifier. In this case the
allowable shunt power will be very low because the capacity is limited by the design.
Conversely, if the drive loading is very low and/or the ambient temperature is reduced,
the capacity to dissipate shunt power is increased. The relationship between the Shunt
dissipation capacity, Heatsink RMS loading and Ambient Temperature is shown in the
following charts.
Heatsink RMS
E
N E Series Only
This parameter is available using the PowerTools Watch Window as a diagnostic tool. It
displays the effective Heatsink utilization based on the power dissipated by the input
bridge rectifier and the output power stage. The value of 100 percent is the maximum
continuous power dissipation available at 40 ° C ambient temperature with zero shunt
activity. The relationship between the Shunt dissipation capacity, Heatsink RMS loading
and Ambient Temperature is shown in the following charts.
Drive Ambient Temperature
E
N E Series Only
The Drive Ambient Temperature parameter is located on the PowerTools "Advanced" tab
in the Detailed Setup View. This tab is not normally visible and it is only rarely necessary.
The Drive Ambient Temperature is a parameter which will let the drive know the air
temperature around the drive heat sink while the system is under normal operating
conditions. If the actual ambient temperature is higher than 40 ° C, setting the Drive
Ambient Temperature parameter to the actual temperature will help to protect the drive
by activating the Shunt Fault at an appropriate time.
The Drive Ambient Temperature parameter determines the total amount of heat the heat
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Operational Overview
43