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 - Brushless, Brushed, Rotary, Voice Coil, Inductive Load.

Command Source(s)

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

PWM & Direction (Direct) - 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.

PWM & Direction (Torque Mode) - 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 - 265 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.

Hall Sensors - Required for commutation of 3Φ brushless motors. ADVANCED Motion Controls servo drives are compatible with 120° and 60° Hall spacing. For selected drives the Hall sensors can also be used for velocity feedback in Hall Velocity mode.

TTL Encoder - 5V incremental encoder feedback. On our analog servo drives, encoders are used for velocity feedback.

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.

Duty Cycle (open loop) - The input command controls the output PWM duty cycle. This mode is used in simple applications where velocity feedback is not available and precise velocity control is not necessary. Similar to voltage mode but not as precise.

Hall Velocity† - The input command controls the motor velocity. This mode uses the motor's Hall sensors for velocity feedback. Due to the low resolution of the Hall sensors, this mode is not recommended for low speed applications. In high speed applications this mode can provide excellent performance.

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