Lenze MC3000 Series - Manual (Page 52)

48 13435743_EDBM301_v14 .0
Refer to the table below:
MAXIMUM DC BRAkE VOLTAGE
MODEL M3100
240 / 120 Vac
MODEL M3200
240 / 200 Vac
MODEL M3400
480 / 400 Vac
MODEL M3500
590 / 480 Vac
24 VOLTS 24 VOLTS 48 VOLTS 59 VOLTS
13 DC TIME (DC BRAkE TIME)
This parameter determines the length of time that the DC braking voltage is applied to the
motor . DC TIME should be set to the lowest value that provides satisfactory operation
in order to minimize motor heating .
NOTE:
If this parameter is set to 999 .9 seconds (the maximum value), the DC braking
will be continuous . If it is set to .0 seconds, it is disabled .
14 DYN BRAkE (DYNAMIC BRAkE)
This parameter enables the dynamic braking circuit . Set this parameter to ON only if the
optional dynamic braking circuit board and resistors are installed .
Dynamic braking is used in applications where high-inertia loads need to be decelerated
quickly . When this is attempted, the motor regenerates voltage back into the drive, causing
the DC bus voltage to rise, eventually resulting in a HI VOLTS fault . With the dynamic
braking option, the DC bus voltage is monitored, and when it reaches a certain level, a
transistor is switched on that connects an external resistor bank across the DC bus . This
allows the regenerated energy from the motor to be dissipated through the resistors as
heat, which keeps the DC bus voltage below the trip level .
16
CURRENT (CURRENT LIMIT)
This parameter sets the maximum allowable output current of the drive, which also
determines the torque capability of the motor . For most applications, CURRENT is left
at the maximum setting, which is 150% or 180% (of the drive’s output current rating),
depending on whether the input voltage is low or high (refer to Parameter 0 - LINE VOLTS) .
Regardless of the CURRENT setting, the drive is capable of delivering a maximum of
150% current for one minute, and 180% current for approximately 30 seconds, before
tripping into an OVERLOAD fault . Refer to Parameter 17 – MOTOR OL .
The drive will enter current limit when the load demands more current than the drive can
deliver, which results in a loss of synchronization between the drive and the motor . To
correct this condition, the drive will enter FREQUENCY FOLDBACk, which commands
the drive to decelerate in order to reduce the output current and regain synchronization
with the motor . When the overcurrent condition passes, the drive will return to normal
operation and accelerate back to the speed setpoint . However, if FREQUENCY
FOLDBACk cannot correct the condition and the drive remains in current limit for too
long, it will trip on an OVERLOAD fault . If the drive enters current limit while accelerating,
the time required to reach the speed setpoint will be longer than the time programmed
into ACCEL (Parameter 8) .