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Source-backed boundaries
Safety, GaN switching (60-100kHz), ADC resolution constraints, I2t limits, thermal derating, and public supplier ratings are separated from one-off claims.
Check whether a 100A class DC servo drive is a real fit for your current envelope, battery voltage drop, and regeneration risk before locking the robot actuator design.
Published July 19, 2026; evidence and assumptions reviewed July 24, 2026. The calculator is a screening tool; final release still requires supplier derating data and thermal validation.
Screen continuous current, peak current, pulse duration, nominal DC bus voltage, and cooling condition before deciding whether a 100A DC servo drive is the right procurement target.
Use phase RMS current; range for this screen is 0.1A to 300A.
Must be equal to or higher than continuous current.
Pulses above 60s should be modeled as continuous thermal load.
Use nominal bus voltage; include min/max pack voltage in RFQ.
Cooling changes whether the result is fit or boundary review.
Enter Arms continuous current
Enter Arms peak current and pulse duration
Enter peak current and pulse duration
Enter nominal battery or DC bus voltage
Safety, GaN switching (60-100kHz), ADC resolution constraints, I2t limits, thermal derating, and public supplier ratings are separated from one-off claims.
Calculator examples cover compact robotics, mobile automation, and direct-drive high-torque axes.
The RFQ list forces continuous, pulse, cooling, DC bus, motor-control, and regeneration evidence into one review.
For the same phase resistance, moving from 50A to 100A creates 4x conduction loss by I^2R. Cooling method matters as much as the advertised current number.
A battery-powered DC drive advertised as 100A may be describing peak current, not continuous current. Ask for continuous current, I2t integration limits, and cooling condition together.
GaN enables 60-100+ kHz switching, reducing current ripple and motor harmonics. However, compact layouts still need IMS (insulated metal substrate), baseplate, or cold-plate integration to protect thermal margin.
If your motion profile demands 100A peak current repeatedly, ensure sufficient low-current time between bursts. Running at 2x continuous current usually restricts the duty cycle to <5-10% to let the drive cool down.
The calculator intentionally screens conservatively. It does not assume that a short pulse above 100A is acceptable, because pulse ratings are supplier-specific and depend on I2t limits, cooling, and repetition rate.
| Input | Why it matters | Screening rule |
|---|---|---|
| Continuous current | Sets average heat load in FETs, copper, connectors, and enclosure surfaces. | If it exceeds the conservative supplier-proof screen, treat the result as a boundary case even when the peak label says 100A. |
| Peak current | Checks whether torque bursts fit the advertised 100A envelope before the I2t accumulator triggers and forces a continuous threshold. | Any value above 100A is outside this page envelope unless a supplier gives a pulse exception. |
| Peak duration | Separates a fast torque impulse from a thermal event that behaves like continuous load. | Longer pulses require a vendor I2t curve, ambient temperature, and repetition rate. |
| DC bus voltage | Checks whether the nominal battery or DC bus range fits the low-voltage drive class before regeneration margin review. | 24V to 60V is the preferred robotics screen; outside it, request min/max pack voltage, under-voltage trip, over-voltage trip, and braking path data. |
| Cooling condition | The same PCB can be safe on a chassis plate and unsafe inside a sealed joint. | Sealed, conduction (IMS/Baseplate), and active cooling use different conservative thresholds. |
The page separates general engineering rules from vendor-specific ratings. Public sources support the safety and technology framing; supplier datasheets must still confirm the exact 100A current envelope for a purchase decision.
Review cycle: refreshed every six months, or sooner when supplier ratings, safety standards, or GaN motor-drive guidance change.
| Source | Supports | Boundary | Date note |
|---|---|---|---|
| IEC 61800-5-1 adjustable speed electrical power drive safety standard | Electrical, thermal, and energy safety must be reviewed for power drive systems, not only motion performance. | Use the standard to frame safety review; it does not publish your vendor-specific current rating. | IEC source reviewed July 24, 2026 |
| Texas Instruments GaN technology and motor-drive guidance | Wide-bandgap GaN devices can reduce switching loss and support high-frequency (60-100kHz) compact power stages. | GaN benefits depend on layout, gate drive, cooling, and EMI validation; do not copy a frequency target blindly. | TI source reviewed July 24, 2026 |
| Motor-drive current sensing constraints | Using a 100A-scaled shunt wastes ADC dynamic range at low currents (e.g. 5-10A), worsening Field-Oriented Control (FOC) resolution. | ADC resolution calculations are implementation-specific; this page uses them as a screening risk, not a finished sensor design. | General engineering limit reviewed July 24, 2026 |
| Synapticon drive documentation for I2t protection | I2t protection is a practical way drives limit accumulated thermal stress by forcing output to a continuous rating once the accumulator is full. | I2t parameters are set by each drive vendor and firmware configuration; request the actual curve before procurement. | Vendor documentation reviewed July 24, 2026 |
| Advanced Motion Controls FE100-50-CM datasheet | A DC servo drive can be sold with separate 100A peak and 50A continuous ratings, so both values must be requested before procurement. | This is one product example, not a universal class rule; verify the chosen hardware revision and cooling conditions. | Supplier product data reviewed July 24, 2026 |
| Elmo Gold Twitter servo drive current-rating table | DC servo drive product pages separate continuous-current rows and peak-current limits, so a 100A inquiry needs the exact model code and rating condition. | Elmo ratings are model-specific; use the table format as evidence to request the exact continuous and peak current definition. | Supplier product data reviewed July 24, 2026 |
| Advanced Motion Controls FE100-50-CM environment data | The same public product evidence that separates 100A peak from 50A continuous also publishes environmental limits, reinforcing that current ratings are tied to stated operating conditions. | This is product-family evidence, not a universal derating rule; require the exact vendor to state ambient temperature, heat-sink or baseplate condition, and current derating curve for the quoted part number. | Supplier datasheet reviewed July 24, 2026 |
| Public example | Current rating | Decision use |
|---|---|---|
| AMC FE100-50-CM FlexPro servo drive | 100A peak current, 50A continuous current | Use as a concrete example that 100A may be a peak rating while continuous current is lower. |
| Elmo Gold Twitter DC servo drive family | Model-specific continuous-current table with peak limit stated separately | Use as a reminder to match the exact part code to both continuous current and peak-current limit before selecting cooling. |
If your result is a boundary case, package the duty cycle, cooling path, ambient temperature, and motor data before asking for a written supplier rating.
Send assumptionsOversizing to 100A can be correct for torque bursts, but it also changes the power path, sensing range, regeneration strategy, and mechanical package.
| Parameter | 40A to 60A class | 100A class | Decision impact |
|---|---|---|---|
| Power path | Lower copper and connector burden | High-current PCB, busbar, or bonded thermal path | A 100A design may need heavier copper, busbars, or parallel FET paths; verify manufacturable trace width and temperature rise. |
| Connector and cabling | Easier routing inside compact joints | Larger contacts and lower-resistance harnessing | Oversizing can make the joint harder to package even when the motor torque looks attractive on paper. |
| DC bus energy | Lower braking energy and ripple stress | Higher bus capacitance and braking path review | Regeneration can trip the DC bus before current capability becomes the limiting factor. |
| Current sensing | Better low-current resolution | Wider range with compromised low-current resolution | Using a 100A-scaled shunt wastes ADC dynamic range at low currents (e.g. 5-10A), worsening FOC resolution unless an auto-ranging CSA is used. |
| Procurement cost | Lower BOM and simpler qualification | Higher drive, thermal, cable, and test cost | Use the smaller class when 100A is only a vague safety margin, not a measured duty-cycle requirement. |
| Thermal headroom | Higher thermal stress and frequent foldback | More headroom, better longevity but larger footprint | If your system frequently hits the thermal limit (I2t foldback) at 100A, oversizing to a 150A class drive can improve system longevity and reduce thermal stress. |
| Tool result | Typical condition | Required action |
|---|---|---|
| Candidate fit | Continuous current stays within the conservative supplier-proof screen and peak is below 100A for a short pulse. | Proceed to supplier quotation with explicit current and cooling clauses. |
| Boundary case | Peak is near 100A, duration is several seconds, or cooling is sealed. | Request thermal simulation, I2t curve, duty cycle review, and mounting details. |
| Electrical boundary | Nominal DC bus voltage is outside the preferred 24V to 60V robotics screen. | Request allowed DC bus range, voltage-sag margin, over-voltage trip, and braking or clamp strategy before quotation. |
| Outside envelope | Continuous current or peak current exceeds 100A. | Move to a larger drive class or reduce the torque requirement. |
| Likely oversized | Continuous current is low and peak current stays below about 60A. | Compare 40A to 60A classes first to improve size, cost, and sensor resolution. |
The highest-impact mistakes are usually not the headline current rating. They are thermal assumptions, regeneration handling, sensing range, and switching/layout validation.
| Risk | Trigger | Mitigation |
|---|---|---|
| Thermal shutdown or unsafe surface temperature | Sustained high current in a sealed or poorly coupled joint | Specify cold-plate cooling (like IMS), ambient temperature, duty cycle, and I2t integration limits in the RFQ. |
| Low-current torque noise | A 100A range is used for a joint that holds position near 1A to 3A | Ask for ADC range, sensor type, current-loop bandwidth, and low-current torque ripple test data. |
| Regeneration over-voltage | High deceleration current pushes energy back to the DC bus | Review battery absorption, braking resistor sizing, and over-voltage trip thresholds. |
| EMI or switching instability | High-frequency GaN switching (60-100 kHz) is used without matching layout and filtering | Validate conducted/radiated emissions, layout parasitics, and low-inductance power loops before freezing the PCB. |
| Question | Why it matters |
|---|---|
| What is the continuous current rating? | Separates true continuous 100A hardware from compact 100A peak marketing claims. |
| What pulse current is allowed, for how many seconds, and at what repetition rate? | Prevents the common error of treating a one-time pulse rating as a robot duty-cycle rating. |
| What cooling surface, ambient temperature, and enclosure assumptions were used? | Makes the thermal number reproducible in the actual robot joint. |
| What DC bus voltage range, under-voltage trip, and over-voltage trip are allowed? | Prevents battery sag or regeneration energy from failing the design after the current envelope looks acceptable. |
| What motor inductance, PWM frequency, and current-loop bandwidth are supported? | Confirms the drive can control the compact joint motor cleanly, not just survive the current. |
| How is regenerative energy handled? | High-current braking can fail through DC bus over-voltage even when torque output is adequate. |
| Case | Input assumption | Outcome |
|---|---|---|
| Humanoid knee jump recovery | 48V bus, 35A continuous, 95A peak, 1.5s pulse, chassis conduction | Candidate fit, but quote must include peak repetition rate and I2t curve. |
| AGV steering actuator | 48V bus, 18A continuous, 45A peak, 2s pulse, sealed enclosure | Likely oversized; evaluate 40A to 60A drive classes for lower cost and better sensing. |
| Direct-drive robot shoulder | 60V bus, 72A continuous, 100A peak, 4s pulse, active cooling | Boundary case; proceed only with thermal test plan and supplier derating data. |
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