Siemens 6RA70 specifications F042 Tachometer fault

Fault

No.

Description
Cause as a function of fault value	Further information (r047.002 to r047.016)
(r047.001, r949.001 or r949.009 with acknowledged error)

F042

Tachometer fault

(active in operating states of – –, I, II)

A check is performed every 20ms to ensure that Actual speed (K0179) is > +5%

Actual EMF (K0287)

If the check result is incorrect for 4 times in succession, the fault message is activated.

The following rule applies:
100% actual speed	= maximum speed
100% actual EMF	= ideal average DC voltage at α ≥ 0, i.e. when the thyristor bridge is fully gated

The ideal DC voltage average value at α = 0 is P078.001∗ 3 ∗ 2

π

The monitoring function is effective only if the EMF > a % of P078.001∗ 3 ∗ 2

π

"a" is a percentage that can be set in parameter P357 (default setting 10%).

The monitoring function is effective only if the armature current is > 2% of the converter rated DC current set in r072.002.

Possible fault causes

♦Open circuit in tachometer or pulse encoder cable.

♦Tachometer of pulse encoder cable incorrectly connected.

♦Pulse encoder supply has failed.

♦Polarity for actual speed value (P743) is incorrectly set.

♦Armature circuit data (P110 und P111) are incorrectly set (execute current controller optimization run).

♦Tachometer or pulse encoder defective

♦Pulse encoder supply voltage is incorrectly set (P140)

♦The field polarity is not reversed by the external hardware when the field is reversed.

Fault value:		r047 Index 002 to 016:
1	Open circuit in tachometer or pulse encoder cable	i002	Actual speed value (K0179) in case of fault
2	Polarity of tachometer or pulse encoder is incorrect	i003	Actual EMF value (K0287) in case of fault

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