Honeywell SmartVFD COMPACT User Manual page 73

Variable frequency drives for constant and variable torque applications

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9.9

OTOR COOLING FACTOR AT ZERO SPEED

The cooling power can be set between 0-150.0% x cooling power at nominal

frequency. See Figure 10.13

par.9.9=40%

Figure 10.13: Motor cooling power

9.10

OTOR THERMAL TIME CONSTANT

This time can be set between 1 and 200 minutes.

This is the thermal time constant of the motor. The bigger the motor, the bigger

the time constant. The time constant is the time within which the calculated

thermal model has reached 63% of its final value.

The motor thermal time is specific to the motor design and it varies between

different motor manufacturers.

If the motor's t6-time (t6 is the time in seconds the motor can safely operate at

six times the rated current) is known (given by the motor manufacturer) the

time constant parameter can be set basing on it. As a rule of thumb, the motor

thermal time constant in minutes equals to 2xt6. If the drive is in stop state the

time constant is internally increased to three times the set parameter value.

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