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PennEngineering Motion Technologies Frequently Asked Questions
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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
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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
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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.
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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
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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
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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
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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.
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