Emerson Control Techniques Epsilon Eb Series Reference Manual page 41

Epsilon Eb and EN Drives Reference Manual
Figure 12: RMS Foldback Trip Point (this graph is accurate to ±5 percent)
Stall Foldback
EN
EN Only
Stall Foldback prevents overheating of the Power Stage. It activates in any mode when the
motor velocity is 100 RPM or less and the Torque Command causes the current to exceed
the stall current threshold for 100 ms or more.
Note
The stall current threshold is not the same as the drives continuous current rating. For
example, the E
N
7 Amps.
Stall Foldback will also be triggered when the drive sees repeated high currents in one of the
three motor phases. This can occur when a motor is indexed back and forth between two of
its electrical poles.
• For 4 pole motors such as MG-205 or MG-208 this distance is 90° mechanical.
• For 6 pole motors such as MG-316 through the MG-4120 this distance is 60° mechanical.
• For 8 pole motors this distance is 45° mechanical.
Once Stall Foldback is activated, the drive current is reduced to 80 percent of the stall current
threshold until the Torque Command Actual is reduced to less than 70 percent of the stall
current threshold for about 200 ms or until the motor velocity exceeds 100 RPM.
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-204 has a continuous rating of 4.5 Amps but a stall current threshold of