D.C. tachometer generator TDP 1,2
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TDP1,2-MANUALen_R5(2018-12-19)ID74713 .doc
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Maximum speed
The maximum speeds listed in the tables are restricted on the one hand by the max. permissible
segment voltage and on the other hand by the permissible peripheral speed. In special cases
appropriate design measures make it possible to exceed the maximum speeds listed in the tables. It
is possible that the maximum speed will have to be reduced when utilizing machines with built-in shaft
seals.
Reversing error
To obtain the same voltage values in both directions the carbon brushes are positioned in the
electrical "neutral zone". When reversing the tacho-generator voltage changes because the contact
surfaces of the brushes are practically never in the neutral zone. There are two causes for the change
in voltage, which results on the one hand from the distortion of the exciter field due to the reaction of
the armature when under load, and depends on the tilt of the brushes in the holder on the other. The
reversing error in the most unfavourable of circumstances is ± 0.5%.
Brushes, brushholder
The quality AG 35 (with 65% silver content) of the silver-graphite brushes guarantees long and
maintenance-free operation.
The combination of silver-graphite brushes with the commutator, which is also silver-plated, causes
a patina to form which ensures that the voltage drop due to contact resistance is very low and
remains nearly constant over a long period of operation. Useful brush life is highly dependent on
the ambient air conditions and the peripheral speed. Under normal operating conditions it is
approx. 20000 operating-hours.
In aggressive ambient air conditions the bakelitebound brush, Quality BG 62, has proved itself. It
does, however, have a higher contact resistance. If the commutator surface is smooth, the patina
should not be removed during regular machine maintenance.
The brush holders used are standard solid double type with a specific brush pressure of 3 N/cm2.
If the machine is likely to be exposed to heavy vibration and shock loads, it is recommended that the
brush holder has a relatively high specific brush pressure of approx. 6 N/cm2. Machines of protection
types IP 56/IP 55 spec. generally have a higher brush pressure.
Summary of Contents for TDP 1,2 Series
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