Section 5: Configuration of the frequency converter
5.13. Operating at frequencies exceeding 50 Hz
The use of a frequency converter enables an output frequency higher than 50
Hz. For typical electric motors with f
n
= 50 Hz, this means operating at a
higher speed than the nominal speed.
Note:
1.
Make sure that the motor manufacturer allows its operation
with a frequency above 50 Hz.
2.
Operating at speeds above the nominal speed may result in, among
other things, shortening of motor life due to faster bearing wear.
3.
Above nominal speed the electric motor operates with constant power.
This means that as the speed increases above nn, the motor shaft
moment will decrease.
Two parameters are responsible for working with a frequency above 50 Hz:
2.12 and 1.40.
Par. no.
Name
Description
par. 2.12
Ref. max.
The maximum value of the reference frequency
(corresponding to 100% of the referencing-unit
value)
par. 1.40
F max.
Maximum output frequency
F max > Ref. max
usually Fmax = Ref. max + 5 Hz
Example settings of par. 2.12 and 1.40 for operation at 70 Hz
par. 2.12 = 70 Hz
par. 1.40 = 75 Hz
TWERD Power Electronics
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