Yaskawa F7 Drive Overvoltage Suppression - Manual (Page 8)

Date: 09/17/2010, Rev: 09-2010 Page 8 of 9 TM.F7SW.062
5.4 Belt Break Detection
If the drive’s output frequency is at maximum frequency for more than 30 continuous seconds, the drive will
assume that the belt or coupling between the motor and the machinery has become disconnected. The
drive will fault on a belt-break fault (B-BRK), energize the fault contacts (MA, MB, and MC), and coast to
stop.
5.5 Heatsink Over-temperature Speed Reduction
If the heatsink temperature exceeds L8-02 (Overheat Pre-alarm Level), the drive’s frequency reference will
automatically be reduced by the percentage set in parameter P2-02. This is done to prevent an Overheat
Fault (OH) by reducing the machine speed and thus it’s loading on the drive. The drive will remain at this
frequency for the time set in parameter P2-01.
While the heatsink temperature is above L8-02, an “OH - Heatsnk Overtemp” alarm will flash. If the
temperature drops below the L8-02 level and before the P2-01 timer expires, “OTDLY - Overtemp Delay”
will flash on the keypad. When the P2-01 timer expires, the drive will accelerate back to its normal
frequency reference.
If the temperature increases back above the L8-02 setting before P2-01 has expired, the timer will be reset.
5.6 Motoring Torque Limits at Start
When a run command is first issued, the drive will internally use parameter P3-01 as both the forward and
the reverse motoring torque limit, for the time specified in parameter P3-02. When the P3-02 time expires,
the torque limit ramps back to the L7-01 & L7-02 values, at a rate determined by parameter P3-03. The
time set into parameter P3-03 represents a torque limit change of 100%. P3-02 can be more than, less
than, or the same as L7-01 or L7-02.
Example: If P3-01 = 200%, L7-01 = 50%, and P3-03 = 2.0 seconds, the torque limit ramp time would be
calculated as follows:
∆Torque Limit = P3-01 – L7-01 = 200% - 50% = 150%
Ramp Time =
∆Torque Limit * P3-03 / 100% = (150% * 2.0) / 100% = 3.0 seconds
Ramp Time = 3.0 seconds.
Figure 3: Motoring Torque Limit at Start