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Q
How much can fan noise be reduced by speed control?
ASpeed control is the most effective lever for reducing acoustic noise: reducing fan speed by 50%, 40%, 30% and 20% lowers noise by approximately 15, 11, 8 and 5 dBA respectively, based on Perseus acoustic measurements in our semi-anechoic chamber. Low-noise blade options and vibration-isolated mounting are also available. Final acoustic levels depend on the system installation; contact us for configuration-specific guidance.
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Q
What is a fan operating point, and why is it different from free-air CFM?
AA fan operating point is the intersection between the fan P-Q curve and the system impedance curve. Free-air CFM is measured at zero static pressure, while installed airflow depends on filters, heat sinks, ducts, guards, and enclosure openings. For defense electronics cooling, selection should be based on the required airflow at the expected pressure drop, not on free-air airflow alone.
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Q
Can Perseus fans operate at extreme low temperatures below -55°C?
AFor very low temperature environments, Perseus fans can be configured with internal heaters and temperature sensors for continuous operation below -55°C. Standard operating range is -55°C to +85°C; extended temperature variants are configuration-specific. In representative cold-environment testing, an evaluated configuration started and operated reliably under defined conditions. Confirm your temperature profile with our engineering team for a configuration review.
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Q
Should I select a cooling fan by static pressure, total pressure, or airflow?
AStart with the required heat removal and installed airflow, then check whether the fan can provide that airflow at the system pressure drop. Static pressure is usually the practical value used to overcome restrictions such as fin stacks, filters, ducts, and compact VPX or avionics enclosures. Total pressure may be reviewed in formal test reports, but product selection should confirm the full operating point.
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Q
Can Perseus fans meet both MIL-STD-461G emissions and MIL-STD-810H vibration limits?
APerseus fans are designed with integrated EMI filtering and mechanical isolation. In representative testing, evaluated configurations have been measured against conducted and radiated emission limits (RE102/CE102, 10 kHz - 18 GHz) and tested at vibration levels representative of fighter platforms (25 g RMS for 10 hours). Because test setups vary by platform, review applicable data for your specific environment with our engineering team.
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Q
Where should axial and centrifugal fans operate on a P-Q curve?
AThe preferred operating region depends on the fan type and system impedance. Axial fans are commonly selected away from stall-prone low-flow regions and should be checked against the actual enclosure resistance. Centrifugal blowers are often used when the system needs higher static pressure through ducts, filters, or dense heat sinks. Final selection should be verified with the model-specific P-Q curve.
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Q
Can one PWM signal control multiple BLDC cooling fans?
AOne PWM command can often be shared by multiple compatible fans when the control reference is correct and the controller can support the electrical interface. The PWM reference should normally be tied to the fan negative return unless an isolated interface is specified. The design should also check pull-up behavior, signal voltage, cable length, and noise immunity before release.
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Q
Can FG or RD feedback outputs from multiple fans be connected in parallel?
AFG and RD feedback outputs should normally be routed separately to the controller. These outputs are commonly open-collector or open-drain style signals, and parallel wiring can hide an individual fan fault or distort the tachometer reading. For redundant cooling trays or multi-fan avionics modules, each fan feedback line should be reviewed as an independent status or speed signal.
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Q
What cooling capacity range do Perseus thermal management solutions cover?
APerseus provides integrated thermal solutions for system heat loads from 100 W to 5,000 W, with heat-flux capability up to 200 W/cm². Methods include forced-air, through-flow air, liquid cooling, phase-change (PCM) storage, micro-channel and TEC cooling. The right solution depends on your heat load, space and environment; our engineering team can perform a thermal assessment for your specific configuration.
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Q
Can a fan feedback wire be used as the PWM ground reference?
ANo. A feedback output such as FG or RD is not a ground return. It may be pulled low, floating, or switching depending on fan status and the external pull-up circuit. Using it as a PWM ground reference can cause unstable speed control, false fault detection, and poor noise immunity. The PWM reference should use the defined fan negative return or an approved isolated interface.
ASpeed control is the most effective lever for reducing acoustic noise: reducing fan speed by 50%, 40%, 30% and 20% lowers noise by approximately 15, 11, 8 and 5 dBA respectively, based on Perseus acoustic measurements in our semi-anechoic chamber. Low-noise blade options and vibration-isolated mounting are also available. Final acoustic levels depend on the system installation; contact us for configuration-specific guidance.
