Asynchronous motor with feedback rotates uncontrolled with low speed during commissioning

Question:

What causes uncontrolled rotation of the asynchronous machine when operated with feedback (C0025 <> 1)?

Answer:

If the motor phases are interchanged the rotary field of motor and feedback system are different. This results, depending on the operating mode, in the following drive performance:

a) U/f characteristic control (C0006 = 5)

• In this case the drive rotates faster by the value set under C0074 (influence speed controller, default setting 10 % of nmax) than the speed setpoint. After the first controller enable the drive cannot even be stopped with speed setpoint = 0 or QSP (quick stop).
• The current which now flows through motor depends on the Umin setting (C0016) and can rise up to Imax (C0022) (OC5 trip possible).

b) Vector control (C0006 = 1), see article on servo inverter Doc-ID 20010152

• In this case the drive rotates slowly with maximum slip speed (depending on motor data and maximum current) and does not react on a speed setpoint. The direction of rotation depends on the sign of the speed setpoint.
• At the same time the maximum current C0022 flows so that the OC5 trip (Ixt monitoring) is released after a delay.