User's Manual

• Current-mode control and current controller

As shown in the block diagram, the current-mode control must be passed through first,

to form the actual current set value for the current controller of the U-conductor current

and of the V-conductor current. The nominal current of the speed controller output

(conductor current) is converted, depending on signals of the resolver, in two current

set values with an offset of 120º and fed to the current controllers for the phases U and

V. The nominal current of the third phase W is imitated by subtraction at the outputs of

the current controller. This guarantees, that the sum of the currents is always zero.

The pulse-width modulator generates from the three d.c. voltage signals for the

conductor currents six PWM signals, which serve for activating the driver stage after

the creation of the lag time.

2.5.3 Driver stage and power amplifier

The driver stage amplifies the signals, coming from the pulse-width modulator and by this

activates the power transistors. MOSFET transistors are used in the power amplifier, which

allows short switching intervals and low residual voltage drop and ensures a good

efficiency.

2.5.4 Monitoring and Fault Logic, Enable

The intermediate circuit voltage and the current in the intermediate circuit are permanently

monitored by the error detection. The device switches off the motor through the error logic

when these values exceed certain quantities. The error logic also reacts when the device

temperature exceeds the allowed values because of insufficient air circulation or a too high

ambient temperature. Restart is possible only after switch-off and switch-on of the supply

voltage.

Now the power amplifier can be enabled at the enable input with an external voltage, the

motor turns.