1014 HEIDENHAIN Technical Manual iTNC 530 HSCI
High harmonic losses in the rotor lead to excessively high bearing
temperatures. One possible remedy, besides increasing the PWM frequency,
is the use of a series reactor.
Here there is no universally valid formula.
The amount of inductance results from the measurement of the bearing
temperature. Furthermore it must be noted that, especially with synchronous
spindles, the motor manufacturer requires a minimum PWM frequency and
minimum inductance of the series reactor depending on this PWM value.
In this context it is important that the heating of (and possible damage to) the
bearing and/or rotor cannot be detected by monitoring the motor winding
temperature
Compliance with the maximum permissible short-circuit current
The short-circuit current IK is calculated from:
• U0: Mesh no-load voltage (see U0 in motor.mot) [VeffL-L]
• XStr1: Stator leakage reactance (see XStr1 in motor.mot) [Ω]
• XH: Magnetizing reactance (see XH in motor.mot) [Ω]
• fN: Rated frequency of the motor (see F-N in motor.mot) [Hz]
This must not exceed the maximum current: IK ≤ IMax
If required, use the speed-dependent PWM frequency switchover in order
to minimize harmonic loss, see page 1082
I
K
U
0
3X
Str1
X
H
2 π f
N
L
Drossel
⋅⋅ ⋅++()⋅
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