Lenze MC3000 Series - Manual (Page 51)

13435743_EDBM301_v14 .0 47
10 MIN FRQ (MINIMUM FREQUENCY)
This parameter defines the lower limit of the drive’s speed range . MIN FRQ is used in
conjunction with MAX FRQ (Parameter 11 below) to define the operating range of the drive .
If MIN FRQ is set to a value above 0 .0 Hz, the drive will ramp up from 0 .0 Hz when given
a start command . Once running, however, the drive will not operate below the MIN FRQ
setting unless the rotation is changed, or a stop command is issued and the drive is
programmed to ramp to a stop .
If the MINIMUM FREQUENCY is set to 0 .0 Hz, the drive may be operated in ZERO SPEED
mode (drive is in RUN state, but there is no output to the motor) . ZERO SPEED operation
can be used in applications requiring the ability to start and stop the drive using only the
selected speed reference . The drive will start when the speed reference is raised above
0 VDC or 4 mA, and it will stop when the reference is lowered to 0 VDC or 4 mA . Note
that the drive must be initially started using one of the normal start commands (keypad
or terminal strip) .
11 MAX FRQ (MAXIMUM FREQUENCY)
This parameter defines the upper limit of the drive’s speed range . MAX FRQ is used in
conjunction with MIN FRQ (Parameter 10 above) to define the operating range of the drive .
WARNING!
Consult motor manufacturer before operating motor above rated
frequency . Overspeeding the motor and/or driven equipment can
cause damage to equipment and injury to personnel!
12 DC BRAkE (DC BRAkE VOLTAGE)
DC braking creates a braking torque by injecting DC voltage into the motor . This parameter
sets the magnitude of that DC voltage . The point at which the drive applies DC braking
to the motor depends on which STOP mode is programmed (either COAST or RAMP,
see Parameter 26 - STOP) .
If the drive is set to COAST, DC braking is activated when the stop command is given .
In this case, DC braking helps decelerate the motor . This is useful in applications where
a quick deceleration is desired on a load that would normally take a long time to coast
to a stop .
If the drive is set to RAMP, DC braking is activated when the output frequency reaches
0 Hz . In this case, the drive decelerates the load to a near stop and then DC braking is
used to stop and hold the motor . This is useful in applications where the load needs to
be stopped in a certain position . Similar applications with high-inertia loads utilize both
dynamic braking and DC braking . The dynamic braking allows the high-inertia load to be
decelerated quickly, while the DC braking stops the load in the desired position .
Due to heat generated in the motor, DC braking should only be used in applications
where the load is stopped infrequently . In high duty-cycle applications, dynamic braking is
recommended because the heat is dissipated through external resistor banks, rather than
in the motor . When used, DC BRAkE should be set to the lowest voltage that provides
satisfactory operation in order to minimize motor heating . The maximum voltage available
depends on the voltage rating of the drive .