A Technical Guide to Custom Versus Standard Servo Drives

January 12, 2025

For most motion control applications, a standard servo drive isn’t just adequate — it’s the best solution. These off-the-shelf units offer a practical balance of proven performance, immediate availability and straightforward integration, making them the go-to choice for many industrial, commercial and consumer equipment.

However, certain applications may extend beyond what standard servo drives can deliver. For example, space constraints may call for varying form factors. Harsh environments may demand protection levels that exceed standard ratings. Precision motion requirements may necessitate algorithms tuned specifically to the motor-load combination. In these and other scenarios, a standard unit simply won’t cut it, making custom drives the optimal solution.

In this white paper, we’ll identify some scenarios and use cases where customization delivers meaningful value — helping you determine when standard drives suffice and when custom solutions justify the investment.

Navigating Physical and Environmental Challenges

The drive’s physical operating environment is one factor that can help you determine whether a standard unit will work or if you’ll need to go custom. Customization often becomes necessary when the operating space is severely limited or when conditions are particularly demanding.

Standard servo drives typically come in panel-mounted or PCB-mounted formats, which work well for conventional installations. However, bear in mind that specialized equipment often has limited real estate for electronics, making standard shapes or sizes impractical. For high-volume OEM customers who don’t need all the connectors and full functionality of a standard enclosed product, ElectroCraft can supply board-only versions extracted from standard products. These boards can be paired with custom heat sinks to achieve the same performance as standard off-the-shelf solutions but in a smaller package — a common customization option for cost-sensitive, space-constrained applications.

Applications requiring an integrated or embedded approach — where the drive must be integrated directly with the motor (called a motor-mounted drive) — represent another scenario of when you may need a custom unit.

Additional examples include systems that can’t accommodate a typical rectangular enclosure. In these cases, you may need non-standard shapes like round drives that mount directly onto motor backs. And in terms of packaging, drives can be customized into ultra-compact PCB assemblies or with adapted standalone chassis mounts to fit specific enclosure or mounting schemes.

Environmental conditions add another layer of complexity in the choice to go custom. Standard commercial and industrial drives aren’t designed for harsh or extreme operating conditions, such as:

• Applications with extreme heat or cold — e.g., ambient temperatures exceeding 100°C or operating outside standard industrial temperature ranges.
• Military and defense systems, which often require drives that meet MIL-SPEC requirements for shock, vibration and temperature extremes.
• Deep-sea and marine applications, which require structural modifications to withstand high pressures at depths reaching several thousands of meters.

Protection against contaminants is another reason for customization. Drive options range from simple protective covers and conformal coating for circuit boards, to full encasement in potting compound for complete contamination prevention. These design modifications matter in industries like food and beverage processing, industrial machinery and agricultural automation.

In one example, ElectroCraft developed an IP69K-rated drive and motor package for an agricultural application where up to fifty drives and motors mounted on a tractor implement automatically control dispensing for each row in the field. This custom solution involved taking the standard drive board and motor, creating a new sealed enclosure and adding waterproof cables and connectors. The IP69K rating ensures the drives can withstand high pressure washdown, in addition to custom hardware that can withstand the extreme vibration and temperature ranges often encountered on farms.

Another example involves a custom drive integrated into a joystick with force feedback (haptic) capabilities for a steering system. The drive had to meet MIL-SPEC requirements for shock, vibration, temperature and ingress protection, which required a conformally-coated drive board in a sealed package.

Matching Power Delivery to Motor and Duty Cycle Requirements

The motor’s duty cycle and size may require power delivery specifications that fall outside the range of a standard servo drive. Because standard servo drives offer fixed ranges of operating voltages and output currents, precisely matching the power source to a specific motor often requires a custom unit. If an application needs current or voltage levels beyond standard specifications — for example, an output between the continuous currents of standard models or a specific voltage for efficient operation — custom drive solutions may be necessary.

One recent customization request came from a large OEM in laboratory diagnostics. The company needed a drive to control a NEMA 34-frame BLDC motor in a low-current application — only 3 to 4A. In addition, the specification also called for a universal AC line input capability; the drive needed to accept 85 to 265V AC anywhere in the world and convert it to DC to run the motor without any jumper settings or physical adjustments.

The customized solution included an integrated power factor controller that reduced harmonics on the AC line while allowing operation at universal voltages — similar to a laptop power supply. This system eliminated the need to size electronics according to the highest voltage (220V) when using 120V, which traditionally meant paying for the higher voltage capability. The power factor controller draws current in phase with the line voltage, producing constant DC power to run the motor at the appropriate stepped-down voltage.

Other important factors are duty cycle and torque requirements. High-acceleration applications — sometimes called pulse-duty operations — demand substantial peak current to generate the peak torque needed for rapid starts and stops. ElectroCraft’s drives typically allow peak current values that are double the continuous rating for a couple of seconds, which is useful for quickly accelerating heavy loads. The drives automatically limit current and reduce performance until operation returns to the continuous range, preventing thermal damage. If the required peak current and continuous current exceed what a standard drive can handle, a custom solution becomes essential to prevent overheating and failure.

Managing Regenerative Braking

Applications requiring regenerative braking represent another scenario where standard drives might not suffice. When motors decelerate under load — common in robotics and electronics manufacturing — they generate energy that flows back into the drive. Many standard drives handle this with an onboard shunt regulator that dissipates the excess energy as heat to keep DC bus voltage safe.

Standard drives have fixed limits for how much regenerative power their internal shunt can handle. Applications with high-inertia loads or vertical axes, like elevators or gantries where gravity assists downward motion, can generate more power than a standard shunt can dissipate. When the regenerative continuous or peak power exceeds these built-in limits, a custom drive with enhanced capabilities or a standard drive with an external shunt resistor module becomes necessary to safely handle the additional energy and prevent drive damage.

Tailoring Control Algorithms for Specialized Motion Profiles

Standard drives come with pre-configured algorithms that work well for typical applications. For example, standard ElectroCraft drives include Advanced Field Oriented Control (FOC) for brushless and closed-loop stepper motors, delivering good dynamic response and acceptable torque ripple for most use cases. The Universal Drive can run brushed DC, BLDC and stepper motors with the unique ability to control steppers as if they were brushless motors using FOC. This feature provides both cost and mechanical advantages; BLDC motors tend to have longer, skinnier form factors while steppers are shorter and wider, giving designers greater mechanical flexibility when space constraints vary.

Additionally, built-in motor databases and preconfigured settings allow you to complete most configurations in seconds, with auto-tuning handling basic optimization. For applications requiring standard velocity control, torque control or basic positioning, these algorithms are more than sufficient.

Customization often becomes necessary when the motor-load combination has characteristics that standard tuning can’t accommodate, necessitating custom control algorithms and feedback processing. For example, applications requiring smooth motion at low speeds, minimal torque ripple or precise tracking may need highly specialized parameter tuning. In these use cases, ElectroCraft can develop custom-tuned FOC algorithms specifically matched to the motor’s electrical characteristics and the application’s performance requirements.

The choice of commutation method also factors into customization decisions. ElectroCraft can implement simple trapezoidal commutation for cost-sensitive or basic applications, or deploy more advanced sinusoidal commutation with custom FOC algorithms when applications demand both high efficiency and superior control resolution.

Integrating Non-Standard Feedback Devices

Another factor for customization involves the use of feedback devices. Standard drives work with common encoders and sensors using industry-standard interfaces. These units typically support Hall sensors for commutation and optical encoders for speed and position, along with Sin-Cos encoders, magnetic encoders, various serial encoder protocols and other feedback types through selectable drive parameter settings.

When applications use proprietary position sensing technology or non-standard feedback devices, however, it’s important to customize the drive to correctly accept, process and communicate those specific signals.

Similarly, while standard drives provide basic fault diagnostics, custom versions can be configured to monitor and report specific internal functions like following error or other application-critical parameters.

Bridging Communication Gaps with Custom Protocols

Beyond modifications to the drives themselves, customization also addresses how servo drives communicate and integrate with broader control systems. Servo drives need to integrate into larger, often complex communication networks and system architectures, with standard units supporting common industrial protocols like CANopen® or EtherCAT®. Applications that require integration with unique, specialized or proprietary networks outside these standard offerings may demand a custom solution.

ElectroCraft has extensive experience creating custom serial-based control protocols (RS-232 and RS-485) when standard interfaces can’t meet an application’s requirements. This capability is particularly valuable for integrating drives with legacy equipment or when a new accessory must work in harmony with existing systems using proprietary communication schemes.

Further, in distributed control systems where drives are located closer to motors, custom features enable the drives to function as intelligent nodes capable of electronic gearing or executing motion-trajectory calculations for tightly coordinated or synchronized axes. These features are important in many industrial automation, medical and lab equipment and semiconductor processing applications, which require advanced control.

Customizing I/O for Enhanced Functionality

Custom I/O is perhaps one of the most frequently requested customizations. In these use cases, custom drives often include modified firmware to add functions to I/O, such as inverting inputs, providing an indicator status or reporting feedback based on control variables. In one example, ElectroCraft created a drive that could be pre-configured to select one of eight configurations automatically based on I/O pin states. Using a custom harness that tied specific pins to ground, the drive could detect and load the appropriate configuration, eliminating manual setup steps.

Making the Decision

Standard servo drives work well when your application fits within typical voltage, current and environmental ratings, requires basic control functionality and uses common form factors and protocols. Custom drives often become necessary in applications with space constraints, harsh environments, demanding power requirements, ultra-precise motion control, non-standard interfaces or advanced features like haptics.

For high-volume OEM customers, customization especially makes sense. Buying larger volumes of drives justifies the development effort, resulting in optimized solutions at a lowest cost per unit. You also avoid paying for unnecessary features while gaining precisely tailored capabilities.

Because standard products serve as an excellent jumping-off point for custom solutions, we recommend starting with standard off-the-shelf options to test and validate performance requirements. If you find the standard drive performs well but needs additional features or modifications, that’s the ideal time to explore customization. This approach reduces risk by proving the basic concept before investing in custom development.

To learn more about standard and custom servo drives, please visit: www.electrocraft.com.