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Source-backed boundaries
Thermal density, DC bus voltage, switching dv/dt, PWM frequency, cooling, and I2t limits dictate low voltage drive performance in sealed enclosures.
Screen current, peak pulse, DC bus voltage, cooling, PWM frequency, and precision-control needs before locking the robot actuator design.
Published July 27, 2026; reviewed July 27, 2026. Screening only; final release requires supplier derating data and thermal validation.
Screen current, peak pulse, DC bus voltage, PWM frequency, and cooling method against the thermal and electrical boundaries of compact low voltage servo drives.
RMS phase current (0.1A - 300A).
Must be ≥ continuous current.
Time allowed for the peak current pulse.
Preferred screen: 24V - 80V; custom review outside 12V - 120V.
Practical GaN band: 40kHz - 150kHz; verify EMI and loss.
Affects the GaN thermal derating ceiling.
Enter Arms continuous current
Enter Arms peak current and pulse duration
Enter peak duration and cooling mode
Enter nominal DC bus voltage
Enter switching frequency in kHz
Thermal density, DC bus voltage, switching dv/dt, PWM frequency, cooling, and I2t limits dictate low voltage drive performance in sealed enclosures.
Calculator examples cover compact robotics, mobile automation, and direct-drive high-torque axes using GaN.
The RFQ list forces current, voltage, pulse, cooling, protocol, switching frequency, sensing method, and EMI evidence into one review.
100A concentrated in a tiny space creates extreme thermal density. Top-Side Cooling (TSC) is often required to bypass PCB thermal via bottlenecks, making the Thermal Interface Material (TIM) the critical link.
A 100A rating on a low voltage drive often means peak limits for fractions of a second due to the tiny thermal mass of the GaN chips. Always verify continuous versus peak.
GaN delivers zero reverse recovery and enables dead-times in tens of nanoseconds (vs 1-2µs for IGBTs), reducing third-quadrant conduction loss and zero-crossing distortion when layout and gate-drive timing are validated.
At 100A, a typical 0.5mΩ shunt resistor dissipates 5W of heat, straining the compact thermal budget. Hall-effect sensors eliminate this loss but introduce magnetic susceptibility.
The calculator intentionally screens conservatively. It does not assume that a short pulse above 100A is acceptable, because GaN pulse ratings are extremely sensitive to I2t limits, cooling, and fast thermal time constants.
Limit: this tool screens current, voltage, PWM frequency, and cooling. Motor type, encoder interface, and command protocol still require supplier confirmation before release.
| Input | Why it matters | Screening rule |
|---|---|---|
| Continuous current | Sets average heat load in GaN FETs, copper, and the drive casing. Tiny GaN chips have minimal thermal buffering. | If it exceeds the cooling-adjusted ceiling, treat the result as a boundary case requiring active cooling or a chassis heatsink. |
| Peak current | Checks whether torque bursts fit the 100A envelope before thermal protection trips due to fast GaN junction heating. | Any value above 100A is outside this envelope. GaN junctions can overheat in milliseconds if pushed beyond rated peak. |
| 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 rigorous thermal interface material (TIM) design. |
| Cooling condition | A low voltage drive that does 100A on an active cold plate may only do 30A inside a sealed robotic joint. | Sealed, conduction, and active cooling dictate the realistic continuous current limit. |
| Nominal DC bus voltage | Voltage class affects GaN device selection, battery sag, regeneration headroom, and whether the drive belongs in a low-voltage robotics architecture. | 24V - 80V is treated as the preferred screen; 12V - 120V needs explicit supplier confirmation. |
| PWM switching frequency | GaN benefits appear through higher switching frequency, but frequency also changes loss, EMI, motor cable stress, and current-loop behavior. | 40kHz - 150kHz is the practical screening band before detailed efficiency, EMI, and control-loop validation. |
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 GaN packaging, thermal derating standards, or supplier guidance changes.
| 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 27, 2026 |
| IEC 61800-3 adjustable speed drive EMC requirements and test methods | High-frequency switching emissions require shielded cables, grounding, and low-parasitic filter designs at system level. | GaN's extremely fast switching generates high-frequency noise (tens to hundreds of MHz). Compliance requires system-level mitigation, not just dv/dt filters. | IEC EMC source reviewed July 27, 2026 |
| CISPR 11 industrial radio-frequency disturbance standard | Industrial equipment radio-frequency disturbance limits must be checked when fast GaN edges, long motor leads, or compact cabinets are involved. | CISPR 11 is an emissions compliance frame, not proof that a specific motor cable, cabinet, or PWM frequency passes testing. | CISPR source reviewed July 27, 2026 |
| Texas Instruments GaN technology and motor-drive guidance | Wide-bandgap GaN devices can reduce switching loss and support high-frequency 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 27, 2026 |
| TI top-side-cooled GaN thermal design application report | Top-side-cooled GaN packages depend on heat-sink interface design, package thermal resistance, PCB layout, and mounting mechanics. | Mechanical design must ensure constant pressure between the GaN device and heatsink without stressing the PCB. | TI thermal source reviewed July 27, 2026 |
| TI GaN-based motor drive power-stage white paper | GaN power stages can support higher-frequency compact motor-drive designs, but fast edges still require layout, EMI, and cable-stress validation. | dv/dt rates are high with GaN; check cable lengths and motor insulation requirements. | TI motor-drive source reviewed July 27, 2026 |
| Industry Standard Current Sensing Trade-offs (Shunt vs Magnetic) | High-precision GaN drives often require shunts for bandwidth, but the I²R heating penalty forces compromises in cooling design in sealed joints. | At 100A, low-ohmic shunts (e.g., 0.5mΩ) still dissipate 5W, requiring thermal management, while Hall sensors offer isolation but lower bandwidth. | Sensing trade-offs reviewed July 27, 2026 |
Current squared scaling means a 100A peak requires 4x the thermal dissipation capacity of a 50A peak. In a low voltage drive, extracting this from small PCB areas is the main bottleneck.
In compact robotics, thermal management is the highest priority risk, followed closely by EMI generated by high dv/dt switching transients.
| Parameter | Why it changes at 100A | Impact on system | Alternative |
|---|---|---|---|
| Thermal Path & Cooling | A 100A Low Voltage design needs heavy copper, busbars, and excellent thermal vias to extract heat from tiny SMDs. Top-Side Cooling (TSC) is highly recommended. | Top-Side Cooling (TSC) bypassing PCB thermal limits | Easier thermal management in tight spaces (Bottom-Side Cooling) |
| Connector and cabling | Oversizing can make the joint harder to package even when the motor torque looks attractive on paper. | Larger contacts and lower-resistance harnessing | Easier routing inside compact joints |
| DC bus capacitance | Regeneration can trip the DC bus. low voltage drives often have smaller DC link capacitors to save space. | Careful braking path review or external regen resistor | Lower braking energy handling |
| EMI and dv/dt | High switching frequencies (100kHz+) can cause EMI. dv/dt filters may be needed for long motor cables. | Proper shielding, grounding, and layout (IEC 61800-3) | Slower switching or shorter cables |
| Gate Driver Dead-Time | GaN lacks a body diode and conducts in the third quadrant. Minimizing dead-time prevents high conduction losses and shoot-through. | Tens of nanoseconds (<50ns) for optimal efficiency | Less critical, IGBTs use 1-2µs |
| Current Sensing Method | Shunts provide high bandwidth needed for GaN control but generate I²R heat (5W at 100A, 0.5mΩ). Hall sensors run cool but have lower bandwidth and magnetic drift. | Low-ohmic Shunt (high precision, high bandwidth) | Hall-effect (avoids 5W heat, isolated) |
Trigger: Sustained high current in a sealed or poorly coupled joint
Control: Specify cooling plate, ambient temperature, duty cycle, and firmware thermal protection state in the RFQ. GaN has low thermal mass.
Trigger: High-frequency GaN switching is used without matching layout and filtering
Control: Validate conducted/radiated emissions, layout parasitics, and motor cable length.
Trigger: High deceleration current pushes energy back to the DC bus
Control: Review battery absorption, braking resistor sizing, and over-voltage trip thresholds.
Trigger: 5W+ continuous heat dissipation from inline shunts in a sealed enclosure
Control: Use isolated Hall-effect sensing if thermal limits are exceeded, or explicitly mount shunts to the top-side cooling plate.
| Scenario | Profile | Tool outcome |
|---|---|---|
| Humanoid knee jump recovery | 35A continuous, 95A peak, 1s pulse, 48V bus, 100kHz PWM, chassis conduction | Candidate fit, but quote must include peak repetition rate, voltage headroom, and junction thermal simulation. |
| Compact AGV steering actuator | 18A continuous, 45A peak, 2s pulse, 36V bus, 80kHz PWM, sealed enclosure | Likely oversized; evaluate 40A to 60A low voltage drive classes for lower cost and smaller footprint. |
| Direct-drive robot shoulder | 72A continuous, 100A peak, 4s pulse, 72V bus, 120kHz PWM, active cooling | Boundary case; proceed only with rigorous thermal test plan and supplier derating data. |
Treat the calculator result as a routing decision. A candidate fit moves to quotation; boundary and outside-envelope results require thermal, voltage, or EMI evidence before procurement.
| Result | Condition | Next action |
|---|---|---|
| Candidate fit | Current envelope, DC bus voltage, PWM frequency, and cooling assumptions all stay inside the screening bands. | Proceed to supplier quotation with explicit current, DC bus voltage, switching frequency, and cooling clauses. |
| Boundary case | Peak is near 100A, duration is several seconds, cooling is sealed, bus voltage is outside 24V - 80V, or PWM is outside 40kHz - 150kHz. | Request thermal simulation, I2t curve, voltage headroom, EMI guidance, and junction temperature (Tj) derating details. |
| Outside envelope | Continuous current or peak current exceeds 100A. | Move to a larger drive class, improve cooling, or reduce the torque requirement. |
| Likely oversized | Continuous current is low and peak current stays below about 60A. | Compare 40A to 60A GaN classes first to improve size, cost, and sensor resolution. |
Send the calculator result with bus voltage, peak duration, PWM frequency, cooling path, motor cable length, encoder type, and protocol target. We will map it to a quotation checklist before prototype sourcing.
Request RFQ reviewHigher switching frequency increases losses; sealed cooling reduces extraction.
TSC bypasses PCB thermal bottlenecks and is often mandatory for reliable 100A continuous operation in compact drives.
GaN junctions heat up much faster than traditional IGBTs/MOSFETs. Pulse durations matter.
GaN requires dead-times in tens of nanoseconds. Excessive dead-time leads to high third-quadrant conduction losses.
With small GaN dies, the TIM is often the dominant thermal resistance.
Fast switching transitions (high dv/dt) cause high-frequency EMI and can damage motor insulation if cables are too long.
The same 100A current claim can be unsafe if battery sag, boost margin, or braking energy exceed the GaN device voltage class.
A drive that fits electrically can still fail the actuator design if EtherCAT/CANopen timing, encoder support, or fault handling is mismatched.
Shunts offer better bandwidth for GaN but add severe localized heating (e.g. 5W at 100A). Hall sensors are thermally neutral but can drift near motor magnetics.
Use these adjacent pages when the same 100A decision shifts from GaN device behavior to motor type, compact packaging, or board-level integration.
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Include voltage, current, motor, encoder, protocol, board envelope, and quantity stage.