Content last revised on July 7, 2026
Mitsubishi QM30TB1-H Darlington Transistor Module Technical Reference
For legacy industrial drives prioritizing thermal margin, this 1000V Darlington bridge module is the optimal choice for thermal longevity. Designed for vintage industrial drives and legacy CNC systems requiring high-reliability bipolar switching, the Mitsubishi QM30TB1-H is a 1000V, 30A 6-in-1 Darlington Transistor Module. Featuring an insulated package with a 2500V AC isolation rating, it combines a peak surge current capability of 300A with a low 0.4 °C/W thermal junction-to-case resistance.
What is the primary benefit of the QM30TB1-H insulated design? It prevents voltage breakdown between active terminals and heatsink. Where is the QM30TB1-H commonly applied? It is widely used in legacy CNC drives and three-phase motor controllers.
Key Parameter Overview
Decoding the Specs for Enhanced Thermal Reliability
| Absolute Maximum Ratings (Tj=25°C unless otherwise noted) | ||
|---|---|---|
| Collector-Emitter Voltage | VCEX(sus) / VCEX | 1000V |
| Collector Current (DC) | IC | 30A |
| Collector Dissipation (per phase) | PC | 310W |
| Isolation Voltage | Viso | 2500V AC (for 1 minute) |
| Electrical Characteristics (Tj=25°C unless otherwise noted) | ||
| DC Current Gain (IC=30A, VCE=5V) | hFE | 75 (Min) |
| Collector-Emitter Saturation Voltage (IC=30A, IB=0.6A) | VCE(sat) | 2.5V (Max) |
| Base-Emitter Saturation Voltage (IC=30A, IB=0.6A) | VBE(sat) | 3.5V (Max) |
| Thermal Characteristics | ||
| Thermal Resistance (Junction to Case, Transistor) | Rth(j-c) Q | 0.4 °C/W (Max) |
| Thermal Resistance (Junction to Case, Diode) | Rth(j-c) R | 1.5 °C/W (Max) |
| Contact Thermal Resistance (Case to Fin, with grease) | Rth(c-f) | 0.25 °C/W (Typ) |
Application Scenarios & Value
Achieving System-Level Benefits in Legacy Motor Drives
Engineers often face issues when dealing with startup current surges in older conveyor belt motors or axis controllers. During starting, the motor demands a peak current far exceeding its normal running rating. The Mitsubishi QM30TB1-H handles this easily due to its high peak surge current rating of 300A. By utilizing this module, developers can build robust industrial systems without fear of instantaneous overcurrent failure.
While the QM30TB1-H is designed for moderate 30A loads, systems requiring higher current handling for larger machinery can utilize the related QM300HA-2H which offers a current rating of 300A. For half-bridge topologies that demand dual-switch configurations instead of a full three-phase bridge, the QM100DY-H provides a 100A, 600V alternative.
When designing retrofits for a legacy servo drive or older VFD, engineers must ensure the power stage meets local harmonic and noise emissions under standards like IEC 61800-3. For engineers performing routine maintenance, a guide on testing modules with a multimeter helps quickly diagnose failing gates.
Technical Deep Dive
A Closer Look at Darlington Switch Topologies for Robust Power Control
The Mitsubishi QM30TB1-H is a 6-in-1 power block comprised of three-stage Darlington transistors. To understand the current gain: the hFE of 75 acts like a mechanical lever. Just as a small force applied on a long lever can lift a massive rock, a tiny base current input of 2A can control a substantial collector current of 30A. This amplification ratio reduces the load on control-side gate drivers, making system integration simpler.
Furthermore, the thermal management of these vintage modules dictates their lifespan. The transistor thermal resistance Rth(j-c) of 0.4 °C/W behaves like a wide highway lane. A narrow lane creates a traffic bottleneck, trapping cars; similarly, high thermal resistance traps heat inside the silicon junction. The low resistance of the QM30TB1-H allows heat to flow rapidly from the junction to the baseplate and heatsink, protecting the module's Safe Operating Area (SOA). This design has been widely integrated into classic motion control applications.
FAQ
Resolving Design and Maintenance Queries for System Engineers
Can the QM30TB1-H be driven directly by voltage-mode gate drivers designed for IGBTs?
No. Since the QM30TB1-H is a current-controlled bipolar device, it requires a continuous base current of up to 2A to maintain the on-state, whereas IGBT drivers typically output voltage pulses to charge capacitive gates.
How does the 0.4 °C/W thermal resistance of the transistor part impact heatsink selection?
A thermal resistance of 0.4 °C/W enables highly efficient heat dissipation. Under full load, applying thermal interface grease with a case-to-fin resistance of 0.25 °C/W is critical to keep the junction temperature below the 150°C absolute maximum.
What isolation safety standard does the isolation voltage rating satisfy?
The isolation rating of 2500V AC for 1 minute allows direct mounting of the module onto a common heatsink. It ensures galvanic isolation, preventing high-power transients from feeding back into the controller electronics.
To verify electrical specifications, mechanical dimensions, or current availability for your legacy system retrofits, contact our sales department or request pricing online.
