Lenze DSD - Manual (Page 400)

15 Results: comparing, optimising, logging
15.6 Reserves with regard to the drive dimensioning
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Lenze · Drive Solution Designer · Manual · DMS 4.2 EN · 12/2013 · TD23
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15.6.8 Reserves for drive systems with an active load
The value to be set with regard to the dynamic reserves for drive systems with an active load (e. g.
hoists or vertical conveyors) must not be too small, because for example hoists in the range of cur-
rent limitation move downwards.
In DSD, motor brakes are only dimensioned as holding brakes, not as service brakes. Additional
checks must be carried out manually. Notes with regard to this subject are included in the DSD pro-
tocol. The use of PM brakes must also be checked in the case of winding applications.
In the case of hoist drives (e.g. cable-guided hoists, vertical lifters via toothed belts, racks and pin-
ions), please observe that permanent magnet holding brakes (type PMB)
• have a significant speed-dependent torque drop which may vary from 100 % of the characteris-
tic braking torque at zero speed to 20 % of the characteristic braking torque.
• cannot safety brake the drive in the lowering phase if the electrical braking via the inverters
fails. Hence, these brakes are not suitable for emergency braking. Use an additional (redundant)
brake outside of the motor or a spring-applied brake (type BFK).
15.6.9 Reserves for drive systems with a passive load
These applications are not so critical with regard to dynamic reserves like those for hoists or vertical
conveyors.
• In order to continuously operate motion applications with a low positioning error, the dynamic
reserves here also are to be at least 15 ... 25 %.
• Motor brakes do not have to have greater reserves for these applications, actually they may
even be smaller than the rated motor torque.

Note!
With regard to a hoist, at least 100 % of reserve should be provided for the dimensioning
of the motor brake!