06.2005 Engineering Information
Siemens AG 6SE7087-6QX70 (Version AE)
SIMOVERT MASTERDRIVES Compendium Motion Control 11-21
11.7 Selection of the braking units and braking resistors
On Compact PLUS units, the choppers for the braking resistors are
provided in the converters and in the rectifier unit (in the case of multi-
axis drives with several inverters).
For further information regarding the selection of the braking resistor,
please refer to the MASTERDRIVES Motion Control Catalog DA65.11,
Chapter 3.
The following criteria apply to the braking resistors:
♦ The maximum braking power which occurs must be smaller than
15
20
. ⋅P . This power must not occur for more than 3 s (see technical
data).
♦ The mean braking power must be smaller than
P
20
45/. with a
maximum cycle time of 90 s
The braking units for Compact and chassis type units are autonomous
components. The braking units, up to a power of P
20
= 20 kW, have an
internal braking resistor. Instead of the internal braking resistor, an
external braking resistor can be used to increase the continuous power
output. The following criteria apply to the selection process:
♦ The maximum braking power which occurs must be smaller than
15
20
. ⋅P . This power must not occur for longer than 0.4 s when there
is an internal braking resistor or 3 s when there is an external
braking resistor (see technical data).
♦ The mean braking power must be smaller than
P
20
36/ when an
internal braking resistor is used or smaller than
P
20
45/. when an
external braking resistor is used. The maximum cycle time is 90 s.
For further information regarding the selection of the braking resistor,
please refer to the MASTERDRIVES Motion Control Catalog DA65.11,
Chapter 3.
The braking power is calculated as follows:
PP
br Mot v Mot Inv
=⋅⋅ηη
P
Mn
Mot v
Mot v Mot
=
⋅
9550
Motor output during braking in kW
M
Mot v
Motor torque during braking in Nm
n
Mot
Motor speed in rpm
The maximum motor braking power
P
Mot v max
generally occurs at the
beginning of deceleration when the motor is running at maximum
speed. If several inverters are operated from one rectifier unit, a check
must be made to see whether several drives can brake simultaneously.
In the event of an emergency stop, all drives may have to be shut down
at the same time.
Compact PLUS
Compact and
chassis type units
Braking power
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