User Manual V 1-4.XX User guide

Applications 9-7
When the motor is stopped, the hold function provides an indefinite
duration of DC current. The level of DC current is set by the DC
Brake Current (parameter 79) level but is limited by 70% of drive
rated current, IT protection, or current limit, whichever is less. This
function is not available when you enable a coast to stop.
To enable DC hold, set bit 7 in Bus/Brake Opts (parameter 13).
Because the actual motor losses are not known when DC hold is
active, you must determine thermally safe operating times and levels.
Check with the motor vendor for DC braking or DC hold application
guidelines. You may also want to consider using external motor
thermal protection.
A limited hold time can be provided by using the DC braking function
with an extended DC brake time.
Using Up to 400% Motor
Current
By default, the 1336 IMPACT drive uses a maximum of 200% motor
current. However, for some applications that use a drive that is
significantly larger than the motor, you may use a maximum of 400%
motor current.
In all cases where the drive current limit (typically 150% of drive
rated current for 1 minute) is less than 400% motor current, the drive
current limit is used to determine the maximum available motor
current. The available current range is shown as the maximum current
limit value in Pos Mtr Cur Lim (parameter 72) and Neg Mtr Cur Lim
(parameter 73).
!
ATTENTION: A hazard of electric shock or motor
movement does exist. When you stop the drive using DC
hold, power is not removed from the motor. You may
want to provide an alternate way to disconnect power
completely from the motor.
!
ATTENTION: DC hold runs for an indefinite period
of time. DC hold becomes active only after you have
commanded a stop. When the stop function completes,
the DC hold function starts. The DC hold continues until
you command a start, disable the drive (enable removed),
or command a coast stop. To issue a coast stop, set bit 8
in Logic Input (parameter 14) or set any type of stop after
configuring the coast stop select in Logic Options
(parameter 17) — coast stop option 1 or 12 per drive set
up.
!
ATTENTION: A hazard of electric shock does exist.
You can only change Bus/Brake Opts when the drive is
disabled. If the drive is enabled, you cannot turn off the
DC hold function by clearing bit 7.
file:
Control
group:
Control Limits