Closed-loop thyristor current control
5-20
System- and communication configuring D7-SYS - SIMADYN D
Edition 06.2002
Additional tasks are executed for four-quadrant drives (4Q).
•
A torque direction is selected, and
•
The changeover sequence controlled
(shift to inverter operation, pulse inhibit, set controller...).
The torque direction is derived from the sign of the complete current
setpoint (SOL.WC1 + .WC2) from a higher-level control. The following
inter-relationship exists:
•
Positive setpoint
Torque direction M1
•
Negative setpoint
Torque direction M2
If a torque direction is not requested, i.e. the setpoint SOL.WC1+
SOL.WC2 < SOL.WCL, the "virtual torque direction M0” is reached and
output SOL.QM0 is set.
The outputs QMx are only controlled from the setpoint.
For 1Q drives, torque direction M2 must be inhibited using a permanent
off command SOL.OF2=1.
The switch-over logic stage calculates, from the calculated
EMF
from
FB–EMF, a pre-control angle with which the current controller is pre-
assigned for torque direction reversal. The value is used with the
selection: Permanent intervention for each calculation.
The switch-over logic stage executes the following commands for switch-
off or changeover:
•
Shift to inverter operation (current is reduced) (SOL.QPI).
•
The system waits until the zero current signal is received from the
SITOR set (SOL.NZM), as soon as the absolute value of the current
actual value (SOL.XC) falls below 3%
•
The pulses are deleted and the hold-off time SOL.THO started
•
The new torque direction is switched-in after the hold-off time
SOL.THO has expired and the pulse cancellation time SOL.TCP.
The no-current interval when the torque reverses is determined by the
I=0 signal and the delay times for the thyristors are between approx. 6.6
and 10 ms (this depends on the motor inductance).
The closed-loop thyristor current control is only enabled with
−
the on command from the switch-over logic stage at input
SOL.ION,
−
the current setpoint SOL.WC1+WC2 > the torque threshold
SOL.WCL, and
−
there is no off command or fault condition.
4Q drive
1Q drive
