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Operational Overview
Shunt Operation
The EN-208 and EN-214 drive models have internal shunt control. The Epsilon and EN-204
have an output function to control an external shunt transistor, but no internal shunt transistor
or resistor.
The E
N-208 has a 50 ohm, 50 watt internal resistor and the EN-214 has a 33 ohm, 50 watt
internal shunt resistor to dissipate regenerative energy generated when braking a motor. The
Epsilon and EN-204 drives rely on the bus capacitors to absorb normal levels of regeneration
energy.
Shunt RMS Fault
This fault activates when the RMS power dissipated in the internal shunt resistor is greater
than allowed based on the heatsink utilization and ambient temperature.
Shunt Power RMS
EN Only
EN
This parameter models the thermal heating and cooling of the drive internal shunt. This
parameter indicates the percent of shunt capacity utilization. When this value reaches 100
percent the drive will generate an RMS Shunt Power Fault. In drives with firmware Rev.
A4 or later. The maximum safe level of shunt power is based on Drive Ambient
Temperature parameter and the power being delivered by the drive as shown in Heatsink
Power RMS. It is also possible to get a Shunt Fault at a value exceeding 100 percent.
Epsilon Only
This parameter displays the shunt output duty cycle in percent. No value of duty cycle will
trigger a shunt fault in an Epsilon drive. When using the Shunt Active output function to
trigger an external shunt switch this can be used to verify actual Regenerative Power
dissipation.
Shunt Active Output
This is a real time indicator of the internal shunt control in the EN drive. On the Epsilon, this
output can be used to connect to an external shunt transistor to dissipate bus energy. This
output is active on all drives and indicates when the bus voltage reaches 415 VDC (393 for
Epsilon). It will shut off when the bus voltage is reduced below 385 VDC.
Shunt Monitoring Algorithm
EN Only
EN
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
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