Technosoft iPOS4808 MX Series, Technical Reference

Page: 65 / 114


Technosoft 2014 63 iPOS4808 MX Technical Reference
2 2
2
NOM MAX
M
U U
E
C



where:
U
MAX
= 39V is the over-voltage protection limit
U
NOM
is the nominal motor supply voltage
E
M
= the overall energy flowing back to the supply in Joules. In case of a rotary motor and
load, E
M
can be computed with the formula:
F
M d
d Ph
2
M final initial L M
2
M L M M
T
2
t
t R 3I ) h - )g(h m (m ) J (J
2
1
E


     
where:
J
M
–
total rotor inertia [kgm
2
]
J
L
–
total load inertia as seen at motor shaft after transmission [kgm 2 ]

M
–
motor angular speed before deceleration [rad/s]
m
M
–
motor mass [kg]
–
when motor is moving in a non-horizontal plane
m
L
–
load mass [kg]
–
when load is moving in a non-horizontal plane
g
–
gravitational acceleration i.e. 9.8 [m/s 2 ]
h
initial
–
initial system altitude [m]
h
final
–
final system altitude [m]
I
M
–
motor current during deceleration [A
RMS
/phase]
R
Ph
–
motor phase resistance [

]
t
d
–
time to decelerate [s]
T
F
–
total friction torque as seen at motor shaft [Nm]
–
includes load and transmission
In case of a linear motor and load, the motor inertia J
M
and the load inertia J
L
will be replaced by
the motor mass and the load mass measured in [kg], the angular speed

M
will become linear
speed measured in [m/s] and the friction torque T
F
will become friction force measured in [N].
Option 2. Connect a brake resistor R
BR
between phase BR/B- (pins A35-A41) and ground (pins
A23+A24+B23+B24), and activate the software option of dynamic braking (see below).
This option is not available when the drive is used with a step motor.
The dynamic braking option can be found in the Drive Setup dialogue within EasyMotion /
EasySetup. The braking will occur when DC bus voltage increases over U
BRAKE
. This parameter
(U
BRAKE
) should be adjusted depending on the nominal motor supply. Optimally (from a braking
point of view), U
BRAKE
should be a few volts above the maximum nominal supply voltage. This
setting will activate the brake resistor earlier, before reaching dangerous voltages
–
when the over-
voltage protection will stop the drive. Of course, U
BRAKE
must always be less than U
MAX
–
the over-
voltage protection threshold.
Remark: This option can be combined with an external capacitor whose value is not enough to
absorb the entire regenerative energy E
M
but can help reducing the brake resistor size.
Brake resistor selection
Kinetic energy Copper losses Friction losses Potential energy