Restart-on-the-fly Description:

The restart-on-the-fly function allows the converter to be connected to a motor which is still rotating. If the converter was to be switched-on without the restart-on-the-fly function, an overcurrent condition would occur, as the flux in the motor has to first be built-up, and the open-loop/closed-loop control must be appropriately set.

NOTE

It is not possible to implement a restart-on-the-fly function for multi-motor drives, as the motors have different run-down characteristics!

The following is executed, depending on whether a tachometer is enabled:

Restart-on-the-fly without tachometer (with search) (P208 = 0):

NOTE

„Restart-on-the-fly without tachometer“ (searching) is only practical for induction motors!

For „restart-on-the-fly without tachometer“, the „Standstill test“ generates a braking torque which can cause drives with low moments of inertia to be braked to a standstill.

♦ A standstill test (a DC current is briefly impressed) is executed after the de-energization time (P371) has expired after the supply returns, with WEA (+ Section 9.1) active, or since the last shutdown time with „OFF 2“ command (inverter inhibit).

♦ If it is identified that the motor is at standstill, energization and acceleration are started as for a standard start

♦ If motor standstill has not been identified, searching is started with the maximum frequency, clockwise phase sequence (P452); if only a COUNTER-CLOCKWISE phase sequence is selected (+ Section 5.1 „Control word“), searching starts with the maximum frequency, clockwise rotating phase sequence (P453).

♦ The search frequency is linearly reduced down to 0 Hz, and more specifically by the search speed which can be parameterized P370 (in Hz, referred to 1 second). In this case the search current P369, which can be parameterized, is impressed.

For P163=3 (closed-loop frequency control), the search current is limited to 200 % of the rated magnetizing current (r196).

• P163 = 1 or 2 (V/f characteristic):

The reference output voltage of the drive converter required for the search current, is compared with the voltage value of the V/f characteristic corresponding to the search frequency.

When the motor frequency is found using this function, the search frequency is kept constant and the output voltage is changed to the voltage value of the V/f characteristic with the energization time constant (dependent on the energization time (P189)).

• P163 = 3 (closed-loop frequency control):

The reference output voltage of the drive converter, required for the seach current, is compared with the search frequency corresponding to the EMF setpoint.

The ramp-function generator is then set to the search frequency.

If it is not possible to set the ramp-function generator, as the supplementary setpoint is too high, then the unit is shutdown with Fault F018 „ramp-function generator could not be set at restart on the fly“.

Otherwise the RESTART-ON-THE-FLY status (013) is exited and the motor (via the ramp-function generator) is ramped up to the actual setpoint frequency.

♦ If the motor was not found, at 0 Hz search frequency, a standstill test is again executed and a search run made in the appropriate direction of rotation when the phase sequence in the other direction of rotation is enabled. The motor is switched-in at 0 Hz even if the search was not successful.

Example: Restart-on-the-fly without tachometer (search)

De-energization time P371 (conditional) Standstill test Search P369,P370 Excitation Acceleration Ref. freq. t f fMAX(RDF) P452 Fig. 9.8 Restart-on-the-fly

Restart-on-the-fly with tachometer (P208 ≠≠ 0):

♦ After the de-energization time has expired (P371), after the supply returns with activated WEA (Section 9.1) or an „OFF2“ command was applied since the last switch-off instant (inverter inhibit), then:

• For V/Hz mode (open-loop control, the drive converter output voltage is linearly increased, within the energization time (P189) from 0 to the V/Hz characteristic value (determined from the measured, smoothed speed actual value.

• For vector controls, the required magnetizing current is established within the energization time.

♦ After the energization time (P189 has expired, the ramp-function generator is set to the smoothed speed actual value.

If it is not possible to set the ramp-function generator, because the supplementary setpoint is too high, then the unit is shutdown with Fault F018 „ramp-function generator was not able to be set for restart-on- the-fly“.

♦ Otherwise, RESTART-ON-THE-FLY status (013) is exited, and the motor is ramp-up to the actual setpoint frequency (via the ramp-function generator.

♦ For closed-loop torque control (P163 = 5) or a slave drive (refer to P587), the drive continues with the actual torque setpoint

Parameter to select the restart-on-the-fly function: P583

Control word bit 23

Restart-on-the-fly enable i001: BASIC

i002: RES

0 to 1

0: Restart-on-the-fly is not enabled.

1: Restart-on-the-fly is enabled at each on command. Source selection parameter for control word bit: P583 + Section 5.1 „Control word“.

Exception: P366 = 3

The automatic restart (+ Section 9.1) and restart-on-the-fly (without taking into account the control word command „restart-on-the-fly enable“ (bit 23)) functions are always activated.

Only for restart-on-the-fly without tachometer (with search) (P208 = 0): P369 Restart-on-the-fly search

current

i001: MDS1

to i004: MDS4

10 % to 400 %

(for closed-loop frequency control, max. 2×r196 realized) Setpoint of the impressed current when searching for the motor (as a %, referred to the rated motor current (P102))

Presetting during „automatic parameterization“ to „no-load motor current“ (r196)

P370 Restart-on-the-fly search speed

i001: MDS1

to i004: MDS4

0.1 Hz to 100.0 Hz

Ramp gradient with which the search frequency can be changed (in Hz, referred to 1 second).

As long as the restart-on-the-fly function is active, the „restart-on-the-fly active“ message is set via the

status word bit 16 (+ Section 5.2).

WARNING

With the „restart-on-the-fly without tachometer“ activated (P366 = 3 with WEA or control word bit 23), the drive may suddenly accelerate as a result of the search current in spite of the fact that the drive is at a standstill and a 0 Hz setpoint ! Death, severe bodily injury or material damage can occur if the drive area is entered!

9.8 Technology controller