The control card contains most of the logic section (see Illustration below). The primary logic element of the control card is a microprocessor, which supervises

and controls all functions of frequency converter operation. In addition, separate PROMs contain the parameters to provide the user with programmable options.

These parameters are programmed to enable the frequency converter to meet specific application requirements. This data is then stored in an EEPROM which

provides security during power-down and also allows the flexibility to change the operational characteristics of the frequency converter.

A custom integrated circuit generates a pulse width modulation (PWM) waveform which is then sent to the interface circuitry located on the power card.

Illustration 3.2: Logic Section

The PWM waveform is created using a control scheme called Advanced Vector Control. Advanced Vector Control provides a variable frequency and voltage to

the motor which matches the requirements of the motor. Also available is the continuous pulsing SFAVM PWM. Selection can be made in parameter F-26, F-27

and F-37, F-38. The dynamic response of the system changes to meet the variable requirements of the load.

Another part of the logic section is the Keypad. This is a removable keypad/display mounted on the front of the frequency converter. The Keypad provides the

interface between the frequency converter's internal digital logic and the operator.

All the frequency converter's programmable parameter settings can be uploaded into the EEPROM of the Keypad. This function is useful for maintaining a backup

frequency converter profile and parameter set. It can also be used, through its download function, in programming other frequency converters or to restore a

program to a repaired unit. The Keypad is removable during operation to prevent undesired program changes. With the addition of a remote mounting kit, the

Keypad can be mounted in a remote location of up to ten feet away.

Control terminals, with programmable functions, are provided for input commands such as run, stop, forward, reverse and speed reference. Additional output

terminals are provided to supply signals to run peripheral devices or for monitoring and reporting status.

The control card logic is capable of communicating via serial link with outside devices such as personal computers or programmable logic controllers (PLC).

The control card also provides two voltage supplies for use from the control terminals. The 24 VDC is used for switching functions such as start, stop and forward/

reverse. The 24 VDC supply is also capable of supplying 200 mA of power, part of which may be used to power external encoders or other devices. A 10 VDC supply

on terminal 50 is rated at 17 mA is also available for use with speed reference circuitry.

The analog and digital output signals are powered through an internal frequency converter supply.

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