As technology continues its shift from analog to digital, we still find strong demand for analog designs. Analog drives provide some attractive benefits:

• Simplicity - It's easy to train your people to set the correct switch and potentiometer settings.
• Proven Track Record - We have been building analog drives since our inception. We have continuously improved our designs to mirror the advances in component technology.
• Performance - When tuned to maximum performance, analog current loops can often times achieve higher bandwidth and faster response than digital current loops.

How can analog outperform digital? It all comes down to the components. In a digital system, A/D conversions and processing time can add delays ranging from 20 to 100 microseconds. This may not seem like a lot, but in the highest bandwidth systems delays of this magnitude create a sizeable phase lag.

The other driving factor is cost. Large volumes and mature designs make prices attractive for everyone (except our competitors).

Setup

Switches and Potentiometers

Motors

All models compatible with - Brushed, Voice Coil, Inductive Load.

Command Source(s)

±10V Analog: Units accept single ended and differential signals.

Direct PWM & Direction - Products with 'DD' and 'BD' in the model number - The user's PWM & Direction signals translate directly to the output. This means the user has direct control of the output duty-cycle and switching frequency. This type of control has the fastest response of all of our products since there are no gain stages or integrators. Since the drive doesn't close the current loop and current limiting is rudimentary (bang-bang current limiting rather than a smooth fold-back) it is up to the user to monitor the current and close the current loop.

Torque Mode PWM & Direction - Products with 'DDC' and 'BDC' in the model number - The PWM signal is converted to an analog voltage in the drive. This voltage is used as the command signal into the current loop just like our other current mode products. This means the user does not have direct control of the output duty-cycle or switching frequency. Instead, the user's input duty-cycle controls the drive's output current.

Power*

DC Voltage Range: 20 - 400 VDC

AC Voltage Range: 45 - 140 VAC

Isolated Ground - Optical isolation between the power ground and signal ground. If the system power is derived from a floating source (such as AC power from the wall) then either the power supply needs an isolation transformer or the servo drive needs built in isolation. Isolation with proper grounding reduces shock hazards and drive failures by keeping the signal ground from floating to dangerous potentials.

Feedback*

Tachometer - Scaled to 60V max.

Mode*

Torque - The input command controls the output current (torque). The servo drive will adjust to disturbances and maintain the commanded current. This is the suggested mode if an external controller is used which can close the velocity or position loops.

Voltage - The input command controls the output voltage. This mode precisely controls the output voltage to the motor. Since motor speed correlates to voltage this mode can be used in simple velocity control applications where velocity feedback is not available.

IR Compensation - The input command controls motor velocity. IR compensation mode can be used to control motor speed without a velocity feedback device. The amplifier compensates for changes in output current. During torque disturbances this mode is not as accurate as a closed loop velocity mode.

Velocity - The input command controls the motor velocity. Drives use high resolution feedback on the motor or load to close the velocity loop.

Additional Options

Additional Options are available for some models - see individual datasheet in the Part Numbering Information section. If the requested option is not in our current product offering it can be made available with sufficient volume. Contact Us for availability.

Indicate the option at the end of the part number. Ex 12A8-INV.

-ANP (Analog Position Loop Mode) - Allows the drive to close the position loop using a potentiometer for feedback.

-INV (Inverted Inhibits) - Pull low to enable / open to disable. This is the inherently safe method to inhibit since a break in the control line will cause the drive to inhibit. For many medium and large drives this option is not required as a separate part number since the function is switch selectable.

-QD (Quick Disconnect) - Plug style connectors on the motor and power lines as opposed to screw-in connectors.

-QDI (Quick Disconnect with Inverted Inhibits) - INV and QD options together.