Fuji Electric P642 Series 6MBP**XT*065-50 Small IPM Application Manual
Document Version: April 2024
Cautions
This instruction contains product specifications, characteristics, data, materials, and structures as of April 2024. The contents are subject to change without notice for specification changes or other reasons. When using a product listed in this instruction, be sure to obtain the latest specifications.
The application examples in this manual show typical uses of Fuji products and do not assure or grant licenses for industrial property rights.
Fuji Electric Co., Ltd. continually strives to enhance product quality and reliability. However, a small percentage of semiconductor products may become faulty. When using Fuji Electric semiconductor products in your equipment, implement adequate safety measures such as redundant, flame-retardant, and fail-safe designs to prevent semiconductor product failure from leading to physical injury, property damage, or other problems.
The products described in this application manual are intended for use in the following industrial electronic and electrical devices requiring normal reliability:
- Compressor motor inverters
- Fan motor inverters for room air conditioners
- Compressor motor inverters for heat pump applications, etc.
If you need to use a semiconductor product in this application note for equipment requiring higher reliability than normal (e.g., transportation equipment, trunk communications equipment, traffic-signal control equipment, gas leakage detectors with auto-shutoff, disaster prevention/security equipment, safety devices), contact Fuji Electric Co., Ltd. for prior approval. Implement backup systems to prevent equipment malfunction if a Fuji Electric product fails.
Do not use products in this application note for equipment requiring extremely high reliability, such as space equipment, airborne equipment, atomic control equipment, submarine relaying equipment, or medical equipment.
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Chapter 4: Details of Inverter Block
This chapter describes guidelines and precautions for circuit design for power terminals, including determining the current sense resistor and external shunt resistor.
1. Connection of Bus Voltage Input Terminal and Low-side IGBTs Emitter
Description of Power Terminals
| Terminal Name | Description |
|---|---|
| P | Positive bus voltage input terminal. Internally connected to the collector of the high-side IGBTs. To suppress surge voltage caused by wiring or PCB pattern inductance, connect a snubber capacitor close to this terminal (typically metal film capacitors). |
| U, V, W | Motor output terminals. Inverter output terminals for connecting to motor load. |
| N(U), N(V), N(W) | Negative bus voltage input terminals. Connected to the emitter of the low-side IGBTs of each phase. For monitoring current of each phase using the external shunt resistor method, connect a shunt resistor between these terminals and power GND. |
| VSC | Low-side sense current detection terminal. Connected to the sense terminal of the low-side IGBTs. Detects sense current shunted from the main current. Connect a sense resistor between the VSC terminal and control GND for short-circuit protection. |
Recommended wiring for shunt resistor and snubber capacitor
- External shunt resistors are used to detect overcurrent (OC) and phase current.
- Long wiring patterns between the shunt resistor and the product can cause excessive surge voltage, potentially damaging the internal control IC and current detection components. Minimize wiring length between shunt resistors and the product to reduce pattern inductance.
- Connect snubber capacitors at the appropriate location to effectively suppress surge voltage, as shown in Fig. 4-1.
- Connecting the snubber capacitor at location "C" is recommended. Location "A" may not suppress surge voltage effectively due to wiring inductance. Connecting at location "B" allows charging/discharging current of the snubber capacitor to flow through the shunt resistor, impacting current detection accuracy and potentially lowering the OC protection level. While "B" offers greater surge voltage suppression than "A" or "C", "C" is recommended for better current detection accuracy.
- A snubber capacity of 0.1 to 0.22 µF is recommended.
[Diagram: Figure 4-1 Recommended wiring of shunt resistor and snubber capacitor showing connection points P, N(U), N(V), N(W), COM, and points A, B, C for snubber capacitor placement relative to the bus capacitor and shunt resistor.]
2. Short Circuit Protection
Two methods are available for short circuit (SC) protection: detecting the sense current shunted from the main current through the low-side IGBTs, or directly sensing the main current with external shunt resistors connected to the N(*) terminals.
[Diagram: Figure 4-2 SC detection circuits, showing two circuit configurations: 'Sense current method' and 'External shunt resistor method'. The external shunt resistor method diagram includes a note: 'When using the external shunt resistor method, connect the VSC terminal to the control GND with the specified sense resistor instead of leaving it open.']
SC protection by sense current method
SC protection operates by feeding back the voltage generated by the sense resistor (Rsc) to the IS terminal. Table 4-2 specifies the sense resistor value and short circuit protection current value.
| Type Name | Sense resistor Rsc | SC protection current (Min.) |
|---|---|---|
| 6MBP50XTA065-50 6MBP50XTC065-50 |
40.2 Ω | 85 A |
| 6MBP75XTA065-50 6MBP75XTC065-50 |
23.2 Ω | 127 A |
- It is recommended to connect an RC filter to the IS terminal input to prevent malfunction of the SC protection circuit due to noise. The RC time constant should be determined based on noise application time and IGBT short circuit capability; a time constant of 1.1µs is recommended.
- For example, to activate SC protection for 6MBP50XT*065-50, Rsc must be set to 40.2Ω or higher. For Rsc, use a resistor with small variation (≤1%), including temperature characteristics, low inductance, and a wattage rating of 1/8W or more.
SC protection by external shunt resistor method
- The sense current method SC protection is intended for short circuit protection against excessive short circuit currents, such as arm or load short circuits.
- For OC protection requiring accuracy, such as motor demagnetization current protection, the external shunt resistor method is recommended.
- When an external shunt resistor is connected, the current split ratio between the main and sense currents varies, affecting the SC protection current value by the sense resistor. Table 4-3 shows the minimum SC protection value with shunt resistors connected.
- If the external shunt resistance is too large, the IGBT saturation current will decrease due to the voltage drop across the shunt resistor affecting the low-side IGBT's gate voltage. It is recommended to set the shunt resistance to 7mΩ or less for 6MBP50XT*065-50, and 4.5mΩ or less for 6MBP75XT*065-50.
- When using external shunt resistors, use low inductance chip resistors to reduce surge voltage during short circuit. Avoid shunt resistors with large inductance, such as cement resistors.
- When using the external shunt resistor method, connect the VSC terminal to the control GND with the specified sense resistor, rather than leaving it open.
| External shunt resistance | OC protection current (Min.) |
|---|---|
| None | 85 A |
| 3 mΩ | 57 A |
| 5 mΩ | 48 A |
3. Setting of External Shunt Resistor for Overcurrent Protection
This section provides an example of selecting an external shunt resistor for OC and SC protection, where OC/SC detection is performed using only the external shunt resistor, bypassing the current sensing method. When using the external shunt resistor method, connect the VSC terminal to the control GND with the specified sense resistor.
Selecting shunt resistor
The shunt resistance value is calculated using the following equation:
RSh = VIS(ref) / IOC (4.1)
- VIS(ref) is the OC protection voltage level, and IOC is the OC protection current level.
- VIS(ref) values are 0.455V (min.), 0.48V (typ.), and 0.505V (max.).
- RSh is the resistance of the shunt resistor. The maximum OC detection level should be set lower than the repetitive peak collector current specified in the product's specification sheet, considering variations in shunt resistance.
- For example, if the OC detection level is set to 100A, the recommended shunt resistance value can be calculated as:
- RSh(min) is the minimum shunt resistance.
- Based on these calculations, the minimum shunt resistance is determined. Select a shunt resistance according to the required OC protection level in practical applications.
RSh(min) = VIS(ref)(max) / IOC = 0.505V / 100A = 5.05 [mΩ] (4.2)
Setting the delay time of OC protection
- An external RC filter is required to prevent malfunction of the OC protection circuit caused by noise. The RC time constant is determined by the noise application time and the IGBT's short circuit capability; a time constant of 1.1µs is recommended.
- When the voltage across the shunt resistor exceeds the OC level, the filter delay time t(delay), which is the time for the IS terminal input voltage to rise to the OC level, is determined by the RC filter's time constant and is expressed by the following equation:
- τ is the RC time constant, and IP is the peak current flowing through the shunt resistor.
- Additionally, there is a shutdown propagation delay td(IS). The total time ttotal from OC detection until IGBT shutdown is given by the following equation:
- Consider the IGBT's short circuit capability for the total delay time. Confirm the appropriate delay time in actual equipment.
t(delay) = -τ · ln(1 - VIS(ref)(max) / (RSh · IP)) (4.3)
ttotal = tdelay + td(IS) (4.4)
