Lenze MCH Series - Manual (Page 52)

48 13435744_EDBMH01_v13
5,6 SKIP FREQ #1 & #2
7 BANDWIDTH
These parameters are used to prevent the drive from operating continuously at critical
frequencies that cause excessive mechanical vibration of the driven equipment. The
SKIP FREQUENCIES (Parameters 5 and 6) and the SKIP BANDWIDTH (Parameter
7) are used to define up to two speed avoidance ranges. The SKIP FREQUENCY
settings define the starting point of the speed range that is to be avoided, and the
SKIP BANDWIDTH setting defines how far the speed range extends beyond SKIP
FREQUENCY. Setting the SKIP FREQUENCIES to .00 Hz disables this function.
Example: The critical frequency is 21 Hz, and a bandwidth of 2 Hz is desired. Therefore,
set SKIP FREQ #1 to 20 Hz and set SKIP BANDWIDTH to 2 Hz. This results in a speed
range from 20 Hz to 22 Hz that the drive will not operate within continuously. If the drive
were operating at 25 Hz and then commanded to operate at a speed within the range
of avoidance, the drive would decelerate to 22 Hz and remain at that frequency until
commanded to 20 Hz or below. The drive would then decelerate through the range of
avoidance to the new frequency. Likewise, if the drive were operating at 18 Hz, and
then commanded to operate at a speed within the range of avoidance, the drive would
accelerate to 20 Hz and remain at that frequency until commanded to a speed of 22 Hz
or above. The drive would then accelerate through the range of avoidance to the new
frequency.
8
ACCEL RATE
ACCEL RATE sets the acceleration time for all speed reference sources (keypad,
speed pot, 4-20 mA, 0-10 VDC, and preset speeds). The ACCEL RATE setting is the
time to accelerate from 0 Hz to the BASE FREQUENCY (Parameter 18). The range of
adjustment depends on horsepower. Refer to the table below.
ACCELERATION LIMITS
HORSEPOWER RANGE OF ADJUSTMENT
0.25 - 20 0.1 - 3600 SEC
25 - 60 0.3 - 3600 SEC
75 - 250 0.6 - 3600 SEC
Example: If ACCEL RATE is set to 30 seconds, and the BASE FREQUENCY is set to
60 Hz, the drive will ramp from 0 Hz to 60 Hz in 30 seconds. This is a linear function,
therefore the drive would ramp up to 30 Hz in 15 seconds, etc.
NOTE:
The ability to accelerate a given load at a particular rate is limited by the
output power capability of the drive/motor combination. The acceleration of
high-inertia and high-friction loads may be affected by the current limiting
characteristics of the drive. Refer to Parameters 16 - CURRENT LIMIT and
19 - FIXED BOOST for more information.
9 DECEL RATE
DECEL RATE sets the deceleration time for all speed reference sources. The DECEL
setting is the time to decelerate from BASE FREQUENCY to 0 Hz. As with Parameter 8
- ACCEL RATE, this is a linear function. If the drive is set to coast to a stop, DECEL will
have no effect when a STOP command is given. The range of adjustment for DECEL
depends on horsepower, voltage, and whether Dynamic Braking (DB) is being used.
Refer to the Deceleration Limits table.