Slip Estimate Messages

"Ind2 Motor Cannot Meet Power Required (Slip Estimate)."

"Ind2 Motor Slip Run Diverged (IMag - Slip Estimate)."

"Ind2 Motor Slip Run Diverged (Slip - Slip Estimate)."

Description – At initialization, in addition to a slew run (see section just above), induction motor models also need to develop an estimate of slip to enter the slew run. Since the torque-slip curve is non-linear, determining this initial estimate again necessitates an iterative technique. These messages appear when the slip estimate cannot be found. Several message types are seen, and these are:

• Cannot Meet Power Required – This message is generated when the full torque-slip curve has been traversed, and no value of torque can supply the power required of the motor.
• Diverged (IMag) – This notes that the iterative estimate method diverged, and that terminal current magnitude triggered the divergence sensor.
• Diverged (Slip) – This notes that the iterative estimate method diverged, and that slip triggered the divergence sensor.

Fix – Review the machine’s terminal conditions (P and Q) and determine if the equipment is indeed being asked to supply power far beyond the unit’s capability. Modify the machine in the power flow case to bring it within an acceptable loading. Alternatively, the model data may be corrupt, and not be representing a reasonable machine characteristic. If you are using your own data, try replacing it with EasyPower-provided model data from the model library. Compare constants to see where your data may be in error.

Odd Root Cause – In the process of running simulations with induction motors, we have found an instance where this message is generated, but the causes above are not at the root of the issue. In one instance we discovered that the base frequency had been set to a high value of 400 Hz, due to a system being created after running a 400 Hz simulation of an airport runway power grid. The high base frequency caused a motor with data specified for 50 or 60 Hz to diverge during the slip estimate.

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Dynamic Stability
Messaging