Technosoft 2019
27
iPOS80x0 BX-CAN/-CAT Technical Reference
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
ϖ
ϖ
−
−
+
+
+
=
where:
J
M
– total rotor inertia [kgm
2
]
J
L
– total load inertia as seen at motor shaft after transmission [kgm
2
]
ϖ
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 [
Ω
]
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
ϖ
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 chopping resistor R
CR
between phase CR / B- and ground, 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 chopping resistor option can be found in the Drive Setup dialogue within EasyMotion / EasySetup:
The chopping will occur when DC bus voltage increases over U
CHOP
. This parameter (U
CHOP
) should be adjusted
depending on the nominal motor supply. Optimally (from a braking point of view), U
CHOP
should be a few volts above
the maximum nominal supply voltage. This setting will activate the chopping resistor earlier, before reaching dangerous
voltages – when the over-voltage protection will stop the drive. Of course, U
CHOP
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 chopping resistor size.
Chopping resistor selection
The chopping resistor value must be chosen to respect the following conditions:
1. to limit the maximum current below the drive peak current I
PEAK
= 20A (for 8010) and 40A (for 8020)
PEAK
MAX
CR
I
U
R
>
2. to sustain the required
braking power
:
d
CHOP
MAX
M
CR
t
U
U
C
E
P
)
(
2
1
2
2
−
−
=
where C is the capacitance on the motor supply (external), i.e:
CR
CHOP
CR
P
U
R
×
<
2
2
3. to limit the average current below the drive nominal current I
NOM
=20A (for 8010) and 20A (for 8020)
Kinetic energy
Copper losses Friction losses
Potential energy
