1. Where the Drive Sits Inside the Cabinet (centered, upper half + cooling clearance)
The photo shows a 55kW VFD panel: the Siemens G120 drive is mountedcentered in the upper halfof the cabinet, with ≥150mm of cooling clearance above it and ≥100mm below. Nothing touches the bottom of the drive, and the cooling air path runs straight from bottom to top. Anaxial fanon the cabinet roof pulls air out, and the bottom air intake is fitted with a dust filter.
2. Braking Unit and Braking Resistor Mounting (mandatory on high-power VFD panels)
The photo shows the braking system of a 75kW VFD panel: abraking unit(Siemens 6SL3000-2DE34-0AA0) is mounted to the right of the drive, and the braking resistor is mountedon the cabinet roof or outside the cabinet(it generates a lot of heat, so mounting it inside requires extra cooling capacity). The braking resistor is wired withhigh-temperature silicone cable(cross-section ≥2.5mm²), sized to the braking current.
3. Cooling System Design in Real Shots (air path + filter + temperature control)
Drive heat loss is calculated at3%–5% of rated power(a 55kW drive, for example, gives off roughly 1.7–2.8kW), so cooling design is critical in a VFD panel:
| Cooling method | Compatible cabinet | Cooling configuration | IP rating |
|---|---|---|---|
| Natural convection | ≤7.5kW low power | Cabinet louvers + bottom air intake | ≤IP30 |
| Forced air cooling | 7.5~55kW | Cabinet-top axial fan + bottom filter | IP30~IP54 |
| cabinet air conditioners | >55kW or IP65 | 300–800W cooling capacity micro air conditioner | IP54~IP65 |
4. VFD Panel Power Circuit and Control Circuit Layout (power and control wiring separation)
As shown in the photo, inside the VFD panel thepower circuit (left) and control circuit (right) are physically separated: the left side carries the power circuit — breaker → contactor → drive — with large-cross-section power cables; the right side carries the control circuit — PLC / relays / terminal blocks — with 0.75mm² signal wires. Between them, ametal dividerprovides separation to suppress electromagnetic interference.
5. VFD Panel Visual Inspection Criteria (judging quality from photos)
① Drive cooling clearance: leave ≥150mm above and below, ≥50mm on all sides; ② braking resistor: use high-temperature silicone wire for connections, mount resistors in a ventilated location; ③ Cooling system: cabinet-top fan + bottom filter, temperature switch set to start/stop automatically at 45°C; ④ Power/control separation: route power and control circuits in separate ducts, spacing ≥200mm; ⑤ Grounding: connect the drive PE terminal to a dedicated PE bar with a grounding conductor ≥4mm².
FAQ FAQ
Does a VFD panel require a cooling fan?
Below 7.5kWnatural cooling is sufficient (cabinet louvers alone); above 7.5kW, a cooling fan is recommended. Above 55kW or in a sealed IP65 cabinet, a cabinet air conditioner is mandatory — otherwise the internal temperature exceeds 55°C and the drive trips on an overtemperature fault.
Should the braking resistor be mounted inside or outside the cabinet?
Low power (≤22kW)the braking resistor can be mounted in a ventilated location inside the cabinet;High power (>22kW)mount it outside or on the cabinet top — the resistor surface can exceed 200°C, and mounting it inside affects other components.
Why leave clearance above and below the drive in a VFD panel photo?
The drive's cooling airflow runs from bottom to top,intake at the bottom, exhaust at the top. Leave ≥150mm above for exhaust, ≥100mm below for intake, and ≥50mm on the sides. Without clearance, heat builds up around the drive and it trips on overtemperature.
Can a contactor be installed between a VFD panel and the motor?
ProhibitedSwitching the output-side contactor while the drive is running produces a high-voltage spike that can damage the IGBTs. If bypass is required, stop the drive first, then operate the contactor.
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