PDL D3-2.5, Instruction Manual, Page: 63 / 113

Microdrive Series Instruction Manual
4201-109 Rev I
63
44, 45 DYNAMIC BRAKE CONTROLS
Screen 44 DB TIME = 10s
Description TIME CONSTANT OF DYNAMIC BRAKE
RESISTOR
Min/Max 0/250
Units SEC
Screen 45 DB DUTY = OFF
Description % DUTY RATING OF DYNAMIC BRAKE
RESISTOR
Min/Max 5/100/OFF
Units %
FUNCTION The Microdrive includes thermal model
protection for a dynamic brake. To protect the
brake resistor the Microdrive will stop
(indicating BRAKE THERM TRIP) when the
calculated use of the resistor exceeds its
rating.
The time constant of the brake resistor is the
time it would take to reach 64% of its final
temperature if continuously energised.
The % duty rating represents the average
percentage of time the resistor may be operated
for.
SETTING UP Leave these screens set at 10s and OFF
respectively unless a Microdrive dynamic brake
option is fitted (the model is active whether a
dynamic brake is fitted or not).
If a dynamic brake option is fitted, these screens
MUST BE CORRECTLY SET according to the
manufacturers resistor specifications. The
dynamic brake thermal model can only protect
the resistor if it is correctly set - never consider
using larger than specified figures.
If a Microdrive dynamic brake option is fitted,
refer to its manual for specifications and
application guidance.
46 SLIP FREQUENCY
Screen 46 SLIP FR=0.0%
Description FULL LOAD SLIP COMPENSATION
Min/Max 0.0/10
Units %
FUNCTION Provides improved speed regulation under
conditions of varying load torque. Load current
is sensed and used to provide a small
proportional increase in frequency to
compensate for the slip of the induction motor
as load changes.
SETTING UP Leave slip compensation set to 0.0% unless
you have a special requirement for improved
speed regulation.
Calculate the full load slip frequency of the
motor and enter this frequency
e.g., for a 1420 rpm, 50Hz, 4 pole motor:
- synchronous speed = 1500rpm
- full load speed = 1420rpm
- slip speed = 1500-1420 = 80rpm
- slip % = (slip speed x 100)
synchronous speed
= (80 x 100)/1500
= 5.3%
Better speed regulation may possibly be
achieved by actually measuring shaft speed
under varying load and experimentally setting
the slip compensation
44
45
46