User manual

Controlinc Digital Futronic VIII User Manual

Model DF320A Version 1.0

(

2003-01-31

)

1.2.2. Variable Frequency Controller Unit (VFC)

Speed of a 3-phase motor is controlled by frequency of the applied power. Operating at 60 Hz will

cause motor to run at normal full speed. Operating at a frequency less than 60 Hz will cause motor to

run a percentage of normal full speed. The VFC can control frequency of the power output from 0.1 Hz

to 400 Hz in 0.1 Hz increments. Variable Frequency Controller (VFC) receives 50 - 60 Hz, single or 3-

phase AC electrical power input and supplies power to the motor of the actuator on command from the

M2CP containing the DCM320A. The AC input power is converted to DC and stored on a bank of

capacitors. The DC power is converted back into 3-phase AC power by switching the transistor outputs

at a high frequency, typically 10KHz. Power is switched in an alternating pattern from positive polarity to

negative polarity to positive polarity, etc. at the frequency rate programmed by the microprocessor to

determine motor speed. Switching polarity is done in a sequence on each of the three phases at a

delay time equal to 120 degrees separation between phases based on the frequency. Frequency is

normally ramped up at a programmed acceleration rate from one frequency to the next higher

frequency. Frequency is also ramped down at a programmed deceleration rate from a higher frequency

to the next lower frequency. Programming the VFC is typically via a front panel keyboard/display

terminal. Some drives may also support programming via special software on a PC. The VFC may be

internal, close coupled or enclosed in a separate enclosure remote to actuator. The VFC must be

located within 500 feet of the actuator. Refer to the VFC operations manual supplied with the VFC

drive for setup and programming instructions.

1.2.3. Modular Construction

Extensive use of surface mount technology (SMT) has allowed EIM to maintain single board

construction of the DCM320A which plugs into the M2CP. The digital control module may be replaced

by plugging in a replacement module without disabling local control functions. EIM has maintained

mechanical gearing of limit and torque switches which keep in step with movement of the actuator

when power is removed without battery back-up. Local control pushbuttons and selector switches are

not dependent on the DCM320A. The actuator is able to operate in the manual mode even while the

DCM320A is removed.