7MBR100UB120 Fuji Electric 1200 V 100 A Power Integrated Module

Content last revised on October 3, 2026

Preventing Spurious Faults: Thermal Feedback and Current Sharing for 7MBR100UB120

Compare each module’s case temperature and measured current when a paralleled power stage reports an intermittent overcurrent fault. A temperature difference can accompany unequal loading, but it does not identify the cause on its own. Check the current sensors, cooling contact, DC connections and gate-drive waveforms against a known-good branch before attributing the trip to 7MBR100UB120.

The module’s 1200 V voltage rating and 100 A current rating are Official Specifications, not a statement that paralleled modules will divide load equally. As a Design Consideration, IGBT conduction voltage can change with junction temperature in a way that helps steady-state current sharing under particular operating conditions. That effect cannot correct unequal gate timing, dissimilar conductor impedance or a poor thermal interface. Designers should establish the device’s applicable conduction characteristics from its original technical documentation and assess sharing across the intended operating range.

For a repair, record the position of each power lead and gate connection before removing the assembly. Inspect for loose terminals, uneven mounting contact and changes to the cooling path. Then compare branch currents at the same operating point, using measurement methods that do not disturb the power loop. If one branch carries more current only during transitions, investigate gate-loop routing and busbar symmetry rather than assuming a static thermal-sharing problem. If the imbalance persists during steady conduction, include thermal contact and connection resistance in the investigation.

Keep the outgoing and return gate-drive paths close together as a Design Consideration to reduce susceptibility to voltage induced by switching current. Match the physical routing of parallel branches where the equipment permits it, while preserving the clearances established by the equipment design. A visually similar replacement layout is not enough: verify gate-to-emitter and collector-to-emitter behavior under controlled operating conditions. Fuji Electric’s PIM product information provides manufacturer context for the module family; the equipment schematic remains essential for identifying the connections in a particular installation.

Benchtop Waveform Tuning: Busbar Geometry and Switching Stress

Probe the collector-to-emitter turn-off waveform at the module terminals when a repaired stage shows a voltage spike or unexplained protection trip. Compare the peak with the operating DC-link voltage and the module’s 1200 V Official Specification, using a measurement setup suitable for the circuit’s voltage and switching speed. A trace captured at a remote bus capacitor may miss voltage developed in the conductors between that capacitor and the module.

As an Engineering Calculation, turn-off peak voltage includes the DC-link voltage plus an inductive contribution that rises with commutation-loop inductance and the rate of current change. This relationship explains why changing the gate drive, busbar path or snubber can alter the measured peak. It does not establish a universal inductance target or snubber value for 7MBR100UB120. Those choices depend on the installed topology and must be checked through switching tests at the relevant operating conditions.

Trace the current loop through the module, DC-link capacitors and return conductor. As a Design Consideration, a compact, symmetrical planar busbar arrangement can reduce loop inductance and make parallel branches more alike. Check whether service work has shifted a conductor, changed its return path or left a joint with poor contact. Examine the capacitor connections as well as the broad busbar surfaces; a short-looking assembly can still contain a consequential narrow or displaced connection.

A snubber capacitor and a metal-oxide varistor serve different roles in an overvoltage network. A local snubber may shape switching transients, while a varistor may address a different surge condition. Neither should be assigned a value from the module’s voltage rating alone. Designers should compare measured switching peaks, the DC-link operating range and the ratings of every connected part before selecting or changing either network. Pro Tip: Keep parallel commutation paths geometrically symmetrical, then verify the resulting turn-off margin with measured waveforms rather than judging the busbar by appearance.

The Fuji Electric power semiconductor portal is a useful manufacturer reference when checking module-family information alongside the equipment drawing. A related module such as 7MBR10UF120 can appear in a review of another power-stage configuration, but its topology, terminals and ratings must be assessed separately; its presence in the same equipment family does not establish an electrical pairing with 7MBR100UB120.

Assembly Integrity and Desaturation Fault Management

Capture the gate command, gate-to-emitter voltage and fault output together when a short-circuit protection event occurs during commissioning. Their timing helps distinguish a genuine high-current event from a disturbed sense path or an unintended gate transition. Check probe references and the driver’s fault-latching behavior before changing protection components.

Desaturation protection is a function of the associated gate-drive circuit, not a protection timing specification established by the 7MBR100UB120 ratings shown here. As a Design Consideration, the driver must recognize abnormal collector-to-emitter voltage during a commanded on-state and turn the device off without creating excessive inductive overvoltage. Blanking behavior, detection thresholds and turn-off shaping belong to the particular driver design. Designers should verify them against the applicable module documentation and measured fault response rather than applying a generic timing target.

Inspect the gate-drive return, sensing connection and isolation components for routing or assembly changes after a repair. A desaturation lead that follows a noisy power conductor can pick up a transient; a compromised return path can also distort the apparent gate voltage. Compare the suspect channel with an operating channel where the circuit architecture permits it. Keep the measurement references consistent, because differences introduced by the test setup can look like differences between drivers.

If the driver uses staged or softened fault turn-off, assess both parts of the response: whether the fault current is interrupted and whether the collector-to-emitter peak remains within the device’s applicable limits. Slower interruption can reduce an inductive spike while changing fault energy, so neither a smooth-looking voltage trace nor a rapid shutdown alone proves the response acceptable. The driver, DC-link layout and module have to be evaluated as one switching system.

For a replacement assessment, the 100 A Official Specification is a starting identity check, not permission to substitute a lower-current unit. The related 7MBR35UB120 may be examined when reviewing Fuji module options, but its different model designation calls for a full comparison of current rating, circuit arrangement, terminal layout, gate-drive requirements and thermal mounting before any equipment-level decision.

Field Diagnostics and Commissioning: Isolation and Terminal Clearances

Measure the equipment’s isolation barrier and inspect the terminal area when a gate fault appears only as the DC link switches. Begin with the equipment’s approved test procedure and disconnected-circuit conditions; an in-circuit reading may include capacitors, surge components or other paths outside the module. Record exactly which terminals and chassis points were tested so that a later reading is comparable.

The supplied Official Specifications identify a Fuji Power Module rated at 1200 V and 100 A; they do not establish a reinforced-isolation rating, a barrier test voltage or a common-mode transient immunity rating for the complete gate-drive assembly. As a Design Consideration, inspect creepage paths and air clearances around exposed terminals after installation, accounting for the equipment’s insulation scheme and service environment. Verify required distances against the applicable equipment documentation rather than inferring them from the module voltage rating.

Common-mode switching transients can disturb an optocoupler or digital isolator on the drive board and appear as a false command or fault. Check the isolator output, driver output and local supply together to locate where the disturbance first appears. Designers should select and validate the isolator against the measured transients and the system’s insulation requirements. The module’s voltage rating alone does not specify an isolator’s transient immunity or certify the finished equipment’s electromagnetic compatibility.

When assessing an industrial inverter welder or medium-frequency induction-heating supply, compare the original circuit arrangement, cooling interface and measured switching behavior before treating 7MBR100UB120 as a fit for that equipment. As a Design Consideration, altitude, insulation environment and long-term reliability questions require system-specific assessment; no field failure rate or service-life figure follows from the two electrical ratings on this page. The Power Electronics Masterclass provides broader selection and reliability context without replacing measurements on the installed assembly.