Asynchronous motors in control mode VFC^PLUS

The VFC^PLUS control mode without encoder allows dynamic use of the entire speed range of the drive. Reversing and moving through the speed 0 are also possible.

However, continuous operation of asynchronous motors without encoder at low speeds is not possible. The minimum speeds that must not be permanently undercut during operation without encoder are:

• Motoring operation: 1% of the asynchronous motor nominal speed
• Regenerative operation: 10% of the asynchronous motor nominal speed

INFORMATION

Lifting application with encoder

The control must be designed in such a way that the direction of rotation can only be changed when it is at a standstill (with the brake closed).

If the direction of rotation should be changed without standstill, a motor encoder must be used.

The described restrictions do not apply in the VFC^PLUS control mode with encoder. In comparison to operation without encoder, higher dynamic properties can be achieved with an encoder.

When determining the maximum speed, note that the breakdown torque M_K is reduced in a quadratic relationship in the field weakening range.