No longer a trend, automation has become the foundation in technology for manufacturing. This article addresses three areas that require new thinking and innovative approaches for next-generation cooling technology manufacturing: where intelligent motion controls are used, whether they increase product life and performance, and what they protect.
For a cooling device that requires customized control and maximum performance, intelligent motion controls add full control functionality to brushless DC fans and blowers for demanding applications that require custom output such as those used in medical devices and robotics. Intelligent motion controls include multiple safety and performance features that allow engineers greater design flexibility in order to optimize system performance and maximize long-term reliability and product life.
The primary function of any intelligent motion control system is the ability to control and fully protect all safety features. That protection prolongs the service life of the cooling fan or blower and increases a system's efficiency. When cooling systems get developed, they get designed for protecting against these critical issues: overheating, aging or wear blade blockages, current surges, and power supply overvoltages. However, environmental conditions alter the behavior of any cooling system. If customized correctly, the intelligent motion control will react intelligently to control protection and maintain a stable operation.
The following section details 16 motion control features to help engineers and designers better understand the benefits of intelligent motion controls for brushless DC fans and blowers.
Inrush Current Protection (IR). With IR control, when the power switch is turned on to supply current to the fan, the current is zero and starts to increase gradually until the fan has achieved its maximum speed at the rated current (see Figure 1). The maximum current at successful startup is equal to the free-running current (or less when the rotor stays locked at startup). The fan will achieve the rated speed within 10 seconds. This built-in control contains no external wire. Benefit: It aggressively protects from current surges.
Auto Start (AS). The AS control with locked rotor protection and restart with current limit guarantees that the fan will automatically restart if the blade is blocked and is released (see Figure 2). When the rotor gets locked, the fan current is reduced to zero. The fan attempts to restart every five seconds. Benefit: It protects automatically if the blade gets blocked.
Frequency Generator (FG). The FG control is an open collector output type. It provides a square wave signal if the open collector is connected to a “pull up” resistor and is powered by the power supply voltage that is compatible with the input of the reading device. The maximum collector voltage may be up to 72 VDC and the maximum collector current is 10 mA. The reading device's power supply must have the same ground potential as the fan. Benefit: It monitors the fan's running speed.
Rotation Detector (RD). The RD control is an open collector type. It contains the same hardware as the FG control. The output signal is low when the fan is rotating and is set high when the fan is stopped or is powered off. Benefit: It indicates whether the blade is rotating (low signal).
Rotation Detector Complement (RDb). The RDb control is an open collector type with the same hardware as the FG control. The output signal is high when the fan is rotating and is set low when the fan is stopped or is powered off. This output can be connected in parallel to the RDb of an array of fans that ends at a single alarm device to warn when any fan has stopped. Benefit: It indicates whether the blade is rotating (high signal).
Life Detection (LD). The LD control is an open collector type with the same hardware as the FG control. The output signal is high when the fan is rotating normally, and it is low when the fan is turning below 70 percent of its rated target speed. Slow rotation may indicate aging or wear of the fan/blower or reduced power supply voltage. Benefit: It indicates whether the blade is rotating
DC Voltage Signal (VPWM). The VPWM control adjusts the speed when applying an external DC Voltage signal. This voltage input (Vin) may have any value from 1 to 20 V (standard value is 1–5 V). The fan speed will vary linearly and is proportional to the percent change of the “Vin” value, corresponding to the same percent change of the maximum speed. The constant speed (CS), inrush current protection (IR), and current limit (CL) controls are included. The maximum fan speed is 5,000 RPM, and the stop point is typically set at 20 percent of the maximum. Benefit: Controls speed via an external DC voltage signal.
Current Signal Control (IPWM). The IPWM control adjusts the speed by applying an external current source signal. This current input (Iin) may have any value from 4 to 50 mA, (standard value is 4–20 mA). The fan speed will vary linearly and is proportional to the percent change of the Iin value, corresponding to the same percent change of the maximum speed. The CS, IR, and CL controls are included. The fan will maintain the minimum speed if Iin <4 mA (Mode “A” operation). The maximum fan speed is 5,000 RPM. Benefit: Controls speed via an external current source signal.
Pulse Width Modulation (PPWM). The PPWM control adjusts the speed by applying a pulse width modulated signal. The frequency may be in the range of 30 Hz to 30 KHz. The maximum pulse height “high” may be from 3 to 10 V. The maximum pulse height low is 0.4 V. The fan speed will vary linearly and is proportional to the percent change of the duty cycle value, corresponding to the same percent change of the maximum speed. The CS, IR, and CL controls are included. The fan will maintain the minimum speed if the duty cycle is less than 25 percent. The maximum possible fan speed is 4,000 RPM. Benefit: Controls speed by applying a PWM signal 30 Hz to 30 KHz.
Overvoltage (OV). OV control detects the power supply voltage and allows operation up to the rated maximum operating voltage (see Figure 3). Typically, the maximum operating voltage is 20 percent over the specified rated voltage (unless otherwise specified). If the power supply voltage increases over the 20 percent limit, the fan will stop running and the power supply current will be reduced to approximately zero. The maximum overvoltage protection range is twice the value of the rated voltage. Benefit: It protects from power supply overvoltage.
Automatic Temperature Control (TPWM). When the TPWM control is applied, the upper and lower temperatures may be selected as well as the choice of maintaining the minimum RPM below the minimum temperature chosen. The CS, IR, and CL controls are included. The NTC thermistor is a 104J (100 K @ 25 °C) type and is included with the fan or blower (either built in or external). For safety reasons, if the NTC thermistor is open or shorted, the fan will run at its maximum speed. Benefit: Controls speed automatically via a temperature sensor.
Manual Variable Resistor Control (RPWM). With RPWM control, the speed can be controlled using an external variable resistor. This resistor may have any maximum value from 10 to 100K. The fan speed will vary linearly and is proportional to the percent change of the resistor value, corresponding to the same percent change of the maximum speed. The CS, IR, and CL controls are included. The maximum fan speed is 4,000 RPM. Benefit: Controls speed manually via an external resistor.
Current Limit Control (CL). With the CL control, the current is limited during the start or restart (AS) period. Benefit: Limits current during restart.
Fixed Constant Speed Control (CSf). The CSf control allows the fan to operate safely over a very large power supply voltage range. For example, if the fan is designed to run at 4200 RPM at the rated voltage of 48 V, the fan will maintain the same RPM even when the supply voltage varies from 48 to 72 V. The fixed CS control is preset internally, and the maximum RPM is the rated RPM. Benefit: It will maintain a constant speed over a wide voltage range.
Programmable Constant Speed Control (CS). The CS control can be implemented by the use of the RPWM control. For example, if the external resistor is made up by an 82K and an 18K resistor, then the center point of these resistors will be the input, which will determine that 82 percent of the rated speed will be the maximum speed of the modified fan (if the resistor ends get reversed, then 18 percent of the rated speed will be the new maximum speed). A very important use of this control is to overcome system impedance variations. The fan can be programmed to run at 20 percent lower of the rated speed at zero pressure. When the fan's static pressure is increased, the fan will be able to maintain the same speed under maximum pressure, thus becoming immune to system impedance variations. Benefit: It maintains a constant speed over a wide voltage range.
Multi-Alarm Connection. When multiple fans are used in an application (usually in a fan tray), it is critical to monitor the proper running state of the fans. It is practical to have a single alarm (sound or light) that will indicate when any of the fans have stopped running. Every fan can include the RD control in order to combine the multi-alarm function into a single alarm indicator.
Engineers and designers of today's medical applications are constantly looking for ways to improve equipment cooling by increasing system performance and energy efficiency and to protect from internal and external factors that can reduce product reliability and life expectancy. DC fans and blowers with intelligent motion controls provide air movement intelligence with custom output, making them ideal for green applications. These innovative controls include in-board circuit designs that can be programmed to reduce voltage fluctuations from power supplies and to protect systems from current surges and overheating.
DC cooling fans and blowers with intelligent motion controls are ideal for medical devices and other applications that require customized control in order to maximize performance. By incorporating fans and blowers with intelligent motion control controls into new or existing cooling system designs, operating efficiency, reliability, and life expectancy are significantly enhanced.
This article was written by Sam Pelonis, President of Pelonis Technologies, Inc., Exton, PA. For more information, visit here.