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PennEngineering Motion Technologies Frequently Asked Questions Page 1 of 7 Frequently Asked Questions .What products does PennEngineering Motion Technologies (PMT) offer? .What information do I need to provide in order for you to help me select an appropriate motor solution for my application? .I've selected a motor configuration from your catalog. How do I compose a part number? .Do I have to run a motor at the rated voltage? .Are your motors and gearmotors reversible? .How do I determine my load torque? .How do I determine the rated current for a motor, or the required current draw of the motor for sizing a power supply or fuse? .How do I determine the rated speed or the speed at a specific torque for a motor or gearmotor? .How do I determine the maximum continuous output power (wattage) of a particular motor? .When do I need to specify ball bearings instead of sleeve bearings? .How can we do reduce audible noise? .How can we reduce electrical noise (EMI/RFI)? .Do your products have any agency approvals, listings, or markings (CE, UL, etc)? .How do I mount a motor? .How do I mount an item (pulley, gear, coupling, etc) on the output shaft? .Where can I find connectors to fit your motor terminals? .What are your standard performance tolerances? .How can we keep the motor temperature to a minimum? .Can I get a replacement for a motor that is utilized in a piece of equipment? .Can I buy replacement brushes, gears, etc? .Do you have a local representative or distributor in my area? What products does Pittman offer? PMT designs and manufactures brush, brushless, and stepper DC motors and gearmotors. We offer a wide variety of standard options including gearboxes, encoders, brakes, RFI suppression devices, and integral brushless motor drives. Additional customer-specified valueadded features can include pulleys, gears, cables, connectors, and modified shafts, just to name a few. PMT specializes in customized motor solutions for OEM's in a wide range of commercial and industrial applications. We also offer a comprehensive selection of standard products available from stock through our Express program. We are continuously expanding our product offering to provide the best possible solutions for our http://www.pennmotion.com/faq_section.html 6/2/2006 PennEngineering Motion Technologies Frequently Asked Questions Page 2 of 7 customers. What information do I need to provide in order for you to help me select an appropriate motor solution for my application? The absolute minimum information required to properly select a motor solution is the supply voltage, available continuous and peak current, load torque, speed at load, and desired motor technology (brush or brushless). It is also helpful to have a description of the application, duty cycle (time on, time off), ambient temperature, and motor size requirements (maximum diameter, length, and weight). Other application details that can be important include radial or axial loads, environmental conditions (exposure to water, dust, humidity extremes, special atmospheres), feedback requirements (encoder resolution), EMI/RFI suppression requirements, and brake requirements. For positioning applications, load inertia, angular displacement, move time, and friction torque can be provided instead of load torque and speed at load. Finally, providing quantity requirements will help us to determine whether your needs are best served with our Express offering or with a custom solution. You may call us at 877-748-8626, fax us at 215-256-1338, or e-mail us at [email protected] with your application requirements or questions. I've selected a motor configuration from your catalog. How do I compose a part number? Given the wide selection of features and options for our motors, the number of valid combinations is enormous. It would be very difficult to institute a part numbering system that accommodated all of these possibilities. For this reason, our part numbering system is not fully configurable. Typically, the first half of the number represents the motor family and some basic options. The second half is sequentially assigned and represents the remaining unique features of a particular unit. Initially, you can simply provide us with the base motor number followed by a description of the remaining features. For example, you could specify the following: . GM9236 with 24V winding, 19.7:1 gearbox with wide-face gears, a 500 cpr 3-channel encoder, ball bearings in the motor, and an output ball bearing in the gearbox . Our customer service department will advise you of the unique part number for that configuration once it has been determined. . The exception is our PittmanExpress program, which offers a selection of stock items listed in the catalog by a complete part number. These products should be specified by these part numbers. Do I have to run a motor at the rated voltage? No. The voltage shown for the available motor windings is listed as a reference voltage, and it is just that. Certain motor parameters, including no-load speed, peak torque, and peak current are voltage dependent. Therefore, a voltage must be chosen in order to show these values. The choice is subjective to a degree, but provides a convenient way of comparing different motor windings. Motors can typically be operated safely from zero to about 125% of their reference voltage. However, speed is dependent on voltage and is also a consideration. There are optimal operating speed ranges for motors as well as maximum recommended input speeds for gearboxes. A general rule of thumb is to maintain motor speeds above 1,000 rpm http://www.pennmotion.com/faq_section.html 6/2/2006 PennEngineering Motion Technologies Frequently Asked Questions Page 3 of 7 for brush-commutated motors, and motor speeds below approximately 6,000 rpm for gearmotors. It is not uncommon to exceed these recommendations for supply voltage or motor speed, but there are tradeoffs involved. It is recommended that you discuss your application with us prior to exceeding these limits. Are your motors and gearmotors reversible? Yes. All of our brush-commutated and most of our brushless units are reversible. The only exception would be a brushless unit with built-in control without the direction input function. Simply reversing the polarity to the motor terminals or leads will reverse the output direction of our brushcommutated units. How do I determine my load torque? The torque requirement for an application can be calculated, measured directly using a torque measuring device (torque watch), or measured indirectly using a DC motor. When using a motor, measure the current draw of the motor under load, and calculate the torque using the equation below: T = (I - INL) x (KT x N x h) Where I = Current T = Torque KT = Torque Constant N = Gear Ratio (Equals 1 if there is no gearbox) h = Gearbox Efficiency (Equals 1 if there is no gearbox) INL = No-Load Current Please be aware that this equation approximates the true load torque and does not take thermal conditions into consideration. The results are reasonably close and suitable for most purposes. How do I determine the rated current for a motor, or the required current draw of the motor for sizing a power supply or fuse? Re-solving the previous equation, the current draw of a motor is given by the equation below: I = T / (KT x N x h) + INL Where I = Current T = Torque KT = Torque Constant N = Gear Ratio (Equals 1 if there is no gearbox) h = Gearbox Efficiency (Equals 1 if there is no gearbox) INL = No-Load Current Maximum continuous torque can be obtained from the catalog specifications and used as the torque value to obtain maximum continuous (rated) current. Please be aware that this equation approximates the true current draw and does not take thermal conditions into consideration. The results are reasonably close and suitable for most purposes. http://www.pennmotion.com/faq_section.html 6/2/2006 PennEngineering Motion Technologies Frequently Asked Questions Page 4 of 7 How do I determine the rated speed or the speed at a specific torque for a motor or gearmotor? The output speed for a motor or gearmotor is given by the equation below: w = [VS - (I x Rmt)] / (KE x N) Where w = Speed VS = Supply Voltage I = Current (Obtained from previous equation) Rmt = Motor Terminal Resistance KE = Back-EMF Constant N = Gear Ratio (Equals 1 if there is no gearbox) Maximum continuous (rated) current can be obtained from the previous equation and used as the current value to obtain the speed at the maximum continuous (rated) torque. Please be aware that this equation approximates the motor speed and does not take thermal conditions into consideration. The results are reasonably close and suitable for most purposes. How do I determine the maximum continuous output power (wattage) of a particular motor? Output power is a product of the torque of a motor and the speed of the motor at that torque. For a motor speed in rpm and a torque in oz-in, the power in watts is given by the equation below : Speed [rpm] x Torque [oz-in] x 0.00074 = Output Power [W] Maximum continuous torque can be obtained from the catalog specifications, and the motor speed at that torque can be obtained from the previous equation to determine the maximum continuous output power. When do I need to specify ball bearings instead of sleeve bearings? Ball bearings are generally recommended over sleeve bearings for applications requiring high speeds, extreme temperatures, excessive radial shaft loads and any axial shaft loads, as well as for use with certain encoders. How can we do reduce audible noise? Audible noise can be generated by bearings, brushes, and gears. What constitutes unacceptable audible noise is a highly subjective matter. To complicate it, the sound generated by a motor has different characteristics once it is mounted in an assembly. Minimizing motor speed tends to help reduce unwanted noise. Pittman can provide special gear materials and types, which can also be beneficial. Additional solutions can be provided upon request if the application is noise sensitive. How can we reduce electrical noise (EMI/RFI)? PMT offers a number of solutions for applications that are sensitive to EMI/RFI emissions. Ferrite beads, chokes, capacitors, and varistors are commonly used for such applications. Ferrite beads simply slip over the wires' insulation, whereas chokes must be soldered in series with the http://www.pennmotion.com/faq_section.html 6/2/2006 PennEngineering Motion Technologies Frequently Asked Questions Page 5 of 7 wires' conductors. Capacitors may be installed from the terminal to ground and/or terminal to terminal. Depending on the unit, they can be mounted internally or externally. Capacitors are generally effective for low-frequency noise (typically below 30 MHz), and ferrite beads for high-frequency noise (generally above 30 MHz). Do your products have any agency approvals, listings, or markings (CE, UL, etc)? In general, our products are not CE labeled. Individual labeling of our products is considered unnecessary as they will ultimately become components within a system, and it is the system as a whole which must conform to the applicable directives in order to earn a CE marking. We will certainly work with our customers to help them meet any necessary requirements to achieve this. This often means that measures must be taken in order to suppress or filter EMI and RFI. We can provide a number of solutions to these problems, including installing capacitors and ferrite beads (please refer to the previous question). Our products are also not listed or approved by Underwriters Laboratories. However, most of our products are capable of meeting the requirements set forth in clause B7, titled "Locked-rotor overload test for D.C. motors in secondary circuits," of Appendix B in Underwriters Labs Inc. Standard for Safety UL-1950. If this is relevant to your application, please contact us to see if the unit in question conforms to this standard. How do I mount a motor? Our standard motors and gearboxes are designed to be mounted by their front face. The front mounting face contains a pilot for centering and a bolt hole pattern for fastening. We can also provide special mounting features on custom units to meet your individual needs. How do I mount an item (pulley, gear, coupling, etc) on the output shaft? There are many techniques that can be utilized to mount components on a shaft. For motors with access to the rear end of the shaft, items can be pressed directly onto the shaft. Access to the rear end is important so that it can be properly supported to prevent damage to the rotor or bearings. Another method is to secure items to the shaft with a setscrew. The presence of a flat on the shaft helps prevent slipping, although it may not be necessary for low-torque requirements. Items can also be secured to the shaft with adhesive. It is advised that the adhesive is applied to the component as opposed to being applied directly to the shaft, and that care is taken to prevent adhesive flowing into the motor and contaminating bearings. Another method consists of drilling a cross-hole through the shaft and securing an item with a pin. Again, care must be taken to support the shaft to avoid damaging the motor. These are just a few examples of the many methods that can be accommodated by Pittman. Each of these methods has advantages and disadvantages, and the decision depends on such factors as the type of component being used, the torque requirement, and the associated cost. We can also provide special shaft features on custom units to meet your individual needs. Where can I find connectors to fit your motor terminals? The terminals on our 6000, 8000, 9000 and 14000 series motors are http://www.pennmotion.com/faq_section.html 6/2/2006 PennEngineering Motion Technologies Frequently Asked Questions Page 6 of 7 designed to mate with standard size receptacles. These receptacles can generally be purchased from suppliers of connector hardware. The terminal specifications for each motor type on which they are available are described in the table below: Motor Series Tab Width Tab Thickness 6000 0.110" 0.020" 8000 0.110" 0.016" 9000 0.110" 0.020" 14000 0.187" 0.020" Motors with flying leads are also available. Furthermore, for custom units, we can provide almost any lead-wire and connector assembly that you would like to specify. What are your standard performance tolerances? A table of our standard manufacturing tolerances for basic motor parameters is shown below: Parameter Tolerance Torque Constant ±12% Back-emf constant ±12% Terminal Resistance ±15% Inductance ±10% Inertia ±10% Motor Torque Losses +30% Motor Friction +50% No-Load Current +30% How can we keep the motor temperature to a minimum? Temperature rise can be minimized by keeping the ambient temperature as low as possible, circulating air around the motor, making sure the motor is not insulated, and mounting the motor to a good heatsink. Additionally, selecting a more powerful motor should decrease the temperature rise if it is an important consideration. Can I get a replacement for a motor that is utilized in a piece of equipment? If you have a motor that needs replacing in a piece of equipment, it is recommended that you first contact the OEM for information on spare motors and parts. The OEM should be the most knowledgeable source of information regarding your needs. Additionally, specific motor configurations are often proprietary to a particular company. If you are unsuccessful with the OEM, check to see if the motor is part of our Express offering. If it is, you may order it from us or from a distributor that carries it. Keep in mind that OEM's frequently modify the motor in some way, so check the specifications carefully to make sure it matches what you need. If you are unsuccessful with the OEM and the motor is not part of our PittmanExpress program, your options are severely limited. The best solution becomes the closest available substitution from our PittmanExpress offering. Please be aware that the form, fit, and function of http://www.pennmotion.com/faq_section.html 6/2/2006 PennEngineering Motion Technologies Frequently Asked Questions Page 7 of 7 the closest available unit may differ significantly from the original. There is no way to guarantee that the new unit would be a suitable replacement. Can I buy replacement brushes, gears, etc? We can typically offer replacement components such as brushes or gears for our products. Please be aware that orders for component parts such as brushes and gears are subject to minimum quantity requirements (the exact requirement can be ascertained by contacting our sales department). Any warranties on units that have had any components replaced are void. Please also be aware that while it is generally technically possible to replace the brushes or brush assemblies, it is not always practical. By the time brushes have finally worn out, significant brush-dust has typically accumulated within the motor. Additionally, the commutator, bearings, and gears have also experienced some degree of wear. These conditions are often impractical to correct and will typically contribute to a reduced time to failure than was experienced with the original brush set. Do you have a local representative or distributor in my area? Please refer to our Sales Office Locator for information regarding a representative in your area: www.pennmotion.com/sales-office.html If your area is not covered by a representative or distributor, please contact us directly. | Home | Contact Us | News | Information Request | Motion Products | Help & Learning Center | | Reps & Distributors | Tradeshow Calendar | Complete Literature Files | http://www.pennmotion.com/faq_section.html 6/2/2006