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Blocking drives
If the load torque is higher than the torque limiting of the sensorless vector control, the drive
is braked to zero speed (standstill). To avoid open-loop controlled mode being selected after
the time p1758, p1750.6 can be set to 1. Under certain circumstances p2177 (Motor blocked
delay time) must be increased.
Note
Exception for reversing drives
It is not permissible to use this setting if the load can force the drive to reverse.
Active loads
Active loads, which can reverse the drive, e.g. hoisting gear, must be started in the open-
loop speed control mode. In this case, bit p1750.6 must be set to 0 (open-loop controlled
operation when the motor is blocked). The static (steady state) torque setpoint (p1610) must
be greater than the maximum occurring load torque.
Note
Loads that can drive the motor
For applications with high regenerative load torques at low speeds, p1750.7 can also be set
to 1 As a result, the speed changeover limits of the motor model are increased and a faster
changeover can be made into open-loop controlled operation.
Permanent-magnet synchronous motors
Standard procedure: Open-loop controlled operation at low speeds
Normally, permanent-magnet synchronous motors are started and reversed in open-loop
controlled operation. The changeover speeds are set to 10% as well as 5% of the rated
motor speed. Changeover is not subject to any time condition (p1758 is not evaluated).
Prevailing load torques (motor or regenerative) are adapted in open-loop operation,
facilitating constant-torque crossover to closed-loop operation even under high static loads.
Whenever the pulses are enabled, the rotor position is identified.
Enclosed Drives
Operating Instructions, 12/2018, A5E36652151A
Setpoint channel and closed-loop control
7.4 Vector speed/torque control with/without an encoder
461
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