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Frequently Asked Questions (FAQ)


What kind of voltage choices are available (AC and DC ranges)?

Rotron specializes in customizing standard offerings for use in most any application, and so has the vertically integrated design capability to accommodate any input voltage. However, Rotron's extensive catalogue already offers many voltage choices for product for both Alternating Current and Direct Current input power.

AC power designs are most commonly:

200VAC (as measured line-to-line) 3-phase
115VAC single-phase
115VAC (as measured line-to-line) 3-phase,
230VAC single phase
230VAC 3-phase
480VAC 3-phase

Rotron DC products are most commonly offered at:

28VDC (operable 18-32VDC)
48VDC
270VDC
12VDC


What speed control options are available (AC and DC)?

Rotron specializes in customizing standard offerings for use in most any application, and so has the vertically integrated design capability to accommodate many speed control schemes. Speed control is integrated into many Rotron standard offerings, on both AC and DC products.

For DC fans and blowers:

0-5VDC input on a sensing line that linearly varies the fan speed 0-100%
4-20mA input on a sensing line that linearly varies the fan speed 0-100%
Multiple discrete speeds controlled by additional pin
Varying input voltage (most DC fans operable between 18-32VDC continuous)

For AC fans and blowers:

Multiple discrete speeds controlled by an additional pin
Controlled using a constant Voltage to frequency (V/F) ratio and varying the frequency to control speed. Please note that V/F control of AC fans may incur a longevity penalty that is not tested by Rotron.
Rotron AC products are typically squirrel-cage induction motor designs, but Rotron also offers Dahlander motors for specialized applications.


How do I integrate a single-phase fan into the system?  How does the capacitor need to be installed?  How many wires do I need?  Neutral included?

Specific integration wiring diagrams are included on single-phase products’ interface drawings. With very few exceptions, single-phase AC products that Rotron sells require a motor-run film capacitor (not available through Rotron) that is to be integrated as shown on the interface drawing. The voltage and capacitance ratings should be strictly followed as deviations in voltage rating will affect reliability and deviations in capacitance will affect performance. The capacitor provides a phase-shift between the two internal phases to produce sufficient start and run torque to ensure reliable operation. Typically, no additional neutral wire is needed.


What effects should I expect from using a different capacitance for single phase fans?

The effect of using unspecified capacitance can vary from inconsequential to catastrophic depending on the how large the variation is. Typically, there exists a small range where variations have little effect, but moving out of that capacitance range changes the performance radically. This can result in lost performance, overheating and possibly the fan not starting. Only testing can truly define this interaction.


How do I find a data sheet?  What do I do if the data sheet isn't online? 

Many data sheets are available on www.Rotron.com through the Product Search. Due to the thousands of configurations available as part of Rotron's extensive catalogue, only a sampling is represented on the website. If a specific fan's data sheet cannot be found on the website, please contact Rotron Sales with the specific part number and a request for a data sheet.


What information is found on the interface drawing?

The interface drawing contains the relevant information needed to properly integrate a Rotron fan or blower into a system. The overall envelope and key mounting parameters are dimensioned, a pictorial description of the label plate, and the electrical wiring is diagramed. Special features, such as a fan's tachometer output via Fan Performance Sensor (FPS) will also be detailed. Notes are listed in the top left of the drawing and may contain pertinent data needed to integrate the fan into the system. The title block in the bottom right of the drawing contains the drawing number (starts with C, indicating a customer-facing drawing) and the part number (typically 9-digits starting with a zero).


How do I use the air curve?

Airflow curves provide, at a minimum, the air performance of a fan in terms of static pressure (given in Inches Water Gauge and Millimeters Water Gauge) as a function of volumetric airflow (given in Cubic Feet per Minute and Liters per Second).Plotted in the same area, the fan speed as a function of volumetric airflow can be found above the performance curve. The speed is given in terms of Revolutions per Minute and the scale is found in the top right of the main plot area.  Other relevant data is plotted as a function of volumetric airflow on up to two additional graphs below the main plot area. These may include internal temperature rise of the fan motor, current or power consumed. Data is collected at room ambient conditions.


What altitudes are Rotron fans rated for continuous operation?

AC designs:

The maximum altitude that a fan can continuously operate at is typically determined by the point the reduced mass flow over the motor can no longer keep internal heating controlled. This typically covers all altitudes aircraft will be certified for, with a typical limit near space environments. 

DC designs:

Typically, the altitude is limited to much lower than AC fans and blowers due to the individual ratings of internal electronic circuit components. This will vary from configuration to configuration, and so should be tested for sensitive applications. Rotron can provide testing services up to a 80,000ft equivalent pressure (temperature held constant).


How are the fans balanced?

Fans and blowers are dynamically and statically balanced through a combination of weight removal via drilling small amounts of material away or weight addition, typically through a heavy barium filled epoxy. The propellers of smaller fans typically only use weight removal, and the exposed nature of the propeller will likely make the balancing pits obvious on visual inspection. These are intentional and promote a long service life of the product. Most blower impellers may use metal clips as balancing weights, but typically would not use weight removal as a means of mass distribution (the notable exception being R-model blowers).


How do I know how much performance a fan will give in an application?

Rotron Technical Service can provide assistance in predicting specific guidance per application. Generally speaking, the fan will operate at no other performance point (for a given speed and constant ambient conditions) than where the system impedance curve crosses the fan's performance curve. Understanding the system impedance will ensure that the operating point is predicted as accurately as possible, but certain assumptions can be made based off the desired operating performance point to make reasonably accurate predictions.

Rotron offers application airflow testing to empirically establish the impedance curve. This involves plotting the static pressure developed as a function of airflow for a representative part. These data values are collected by use of Rotron’s in-house aerodynamics test chamber, which uses the counter-blowers to establish the airflow through the part.


How do I predict how much a change in density will affect my fan's performance?

Rotron fans are designed to be constant flowrate machines, meaning that a change in density is unlikely to substantively change the volumetric flowrate for a given fan speed. The static pressure will change in accordance with ratios that become apparent when applying the ideal gas law. Please note that most Rotron fans do not employ speed control, so the aerodynamic unloading of a propeller or impeller may have significant effects on fan speed, and therefore both volumetric flowrate and static pressure can be affected. Rotron Technical Assistance can be contacted for specific guidance.


How do I predict the change in performance due to temperature?

A temperature change will primarily manifest itself as a change in density to an operating fan. Rotron fans are designed to be constant flowrate machines, meaning that a change in density is unlikely to substantively change the volumetric flowrate for a given fan speed. The static pressure will change in accordance with ratios that become apparent when applying the ideal gas law. Please note that most Rotron fans do not employ speed control, so the aerodynamic unloading of a propeller or impeller may have significant effects on fan speed, and therefore both volumetric flowrate and static pressure can be affected. Rotron Technical Assistance can be contacted for specific guidance. Rotron Technical Assistance can be contacted for further information for a specific configuration's operation during extreme temperature excursions.


How do I read the FPS output?

The interface drawing contains the relevant information needed to properly integrate a Rotron fan or blower into a system. The specific wave characteristics of the FPS output are to be interpreted at the system level and are described in detail on the interface drawing for a given part number. Rotron Technical Assistance can be contacted for more information about specific parts.


Do I have to use the FPS line?

The FPS output line is not required to be used on fans so equipped. When not used, the lead should be clipped or otherwise insulated from contact.


What happens to FPS output if input voltage changes?

Depending on the type of fan (AC or DC) and design particulars, the FPS output voltage magnitude may vary based on the input voltage. In all cases, the FPS output frequency still represents the speed of the fan. For DC fans that output a 5V or 6V signal, the FPS voltage magnitude is not affected by input voltage variations within the operational voltage range of the fan. For DC fans that output a 12V signal, the FPS voltage magnitude will vary within a nominal ± 4V over the operational voltage range of the fan. For AC fans, the most common output is an open collector to which the customer must provide the DC power and pullup resistor, so is dependent on the customer power supply voltage alone.


Can I implement a warning device?

Rotron maintains the vertically integrated design and manufacturing capabilities to provide warning devices in most fans and blowers. The standard warning device triggers an output when fan speed is sufficiently slowed. However, Rotron has experience with a wide range of warning device (including speed, power availability, temperature, etc.).Rotron Sales can be contacted to discuss in detail and help find the right solution for a specific application. Many fans output a tachometer signal via the Fan Performance Sensor, and the description of that signal can be found on the interface drawing. This tachometer output is often very useful in creating an alarm at the system level.


What happens if the fan stops spinning (can get into LSWD and Locked Rotor options)?

A fan that is energized and not spinning does not provide the intended function. This condition can occur from material ingestion (FOD) that locks the rotor, bearing failure, or electrical failure internal to the fan. Unless otherwise noted on the interface drawing, most Rotron fans are not internally protected from a locked rotor condition (fan not spinning when energized) and may overheat due to a lack of mass flow over the motor. Rotron can provide Low Speed Warning Detectors (LSWDs) and tachometer outputs (Fan Performance Sensors, or FPS) as options for detecting this condition, and also internally controlled locked rotor protection circuits that prevent overheating.


Are Rotron fans rated for water submergence?

In general, Rotron product is rated for 100% humidity and condensation drip environments, but rarely rated for water submergence. This is typically a capability that has to be carefully designed into a bespoke configuration for an application, and Rotron does have the vertically integrated design and manufacturing capabilities to provide a solution for this type of need. Unless the interface drawing specifically calls out water submergence ratings, it is a best practice to avoid large incursions of water (wave slap, fording, etc.) to the fan or blower.


Are Rotron products REACH or RoHS compliant?

Rotron product is rarely compliant with either REACH or RoHS. Rotron typically relies on various chemicals of concern in the effort to maximize operational reliability. Each fan and blower configuration can be reviewed and compliance determined on request.


What happens to a fan in a locked rotor condition?  Is there protection needed at the system level?  If so, what kind is recommended?

A locked rotor condition prevents a back-EMF to be produced by the rotor, meaning that current in the stator is allowed to rise to the point that thermal damage can occur in the stator wire (I2R losses).Some fans (part number specific) have some protection built in to prevent significant damage to the fan, but is accomplished by shutting down the fan.

AC fans: 

Rotron does not build in specific protection against a locked rotor condition, but can provide a thermal switch. The thermal switch will create an open circuit for the windings, allowing them to cool. Rotron can design a fan that automatically attempts to restart once the stator has cooled sufficiently or that requires a command on signal or manual reset to attempt restart. 

DC fans:

DC electronics can allow for sophisticated controls, as the rotor position detection allows for a logic-based determination of fan operability. These controls include automatic restart attempts with a pre-programmed cool-down interval. System communication capabilities can also be incorporated to allow the application to dictate when the fan can restart.


What are Rotron fans qualified to?  Is the data sheet accurate to Mil-Std-810C?

Rotron uses best design practices to ruggedize all newly introduced configurations similar to the requirements found in MIL-B-23071/28873 (depending AC or DC) and MIL-STD-810 (the current revision as of the date of product release) for many of the environmental tests. Due to the age of some of Rotron's designs, MIL-STD-810C should be seen as a baseline. Rotron does not routinely qualify individual configurations, as the preponderance of Rotron customers choose to qualify the fan as part of the overall system. Rotron can discuss individual part numbers' qualification status through the Business Development team, who handles Applications Engineering responsibilities for Rotron. Rotron is vertically integrated with testing facilities and equipment to be able to qualify our fans and blowers to specific requirements on an as-needed basis, typically defined by a customer specification against which Rotron will document a specialized configuration to meet.


How does changing the frequency of AC input power affect the operation of the fan?

Rotron AC powered products use squirrel cage induction motors. As such, our fans and blowers operate at a speed defined by the input frequency. Intentional manipulation of the input frequency will allow for control over the airmover's speed, but it is important to maintain a constant Voltage-to-Frequency (V/F) ratio.  Maintaining this ratio will minimize the risk of motor damage from thermal excursion. It should be noted that a typical Rotron motor is not wound with specialized wiring for square-wave AC input, and so a shortened life can be expected from the rapid current excursions realizing increased power losses through the windings as that input power swings from maximum positive voltage to maximum negative voltage instantly. The more like a sine wave the input power, the better for increasing fan life.

For AC fans operating at 400Hz, the voltage and frequency limits are 108V to 118V RMS and 393Hz and 407Hz respectively. AC Fans that operate at 60Hz have a voltage range of 105V to 125V and a frequency range 59.5Hz to 60.5Hz.


What is the phase sequence for 3-phase Rotron product?

The phase sequence is defined on the interface drawing for Rotron products, and can also be found on the label plate for 3-phase devices. It is not important to match any particular color wire with what might be called 'Phase 1' or 'Phase A' at the system, but rather it is only necessary that the phase sequence of the input power match the order that the wire color is listed on the label and drawing.