Engineering FAQ
What is the difference between
Unipolar and Bipolar?
What
are the advantages of Micro stepping?
How do you control resonance in your application?
What do I need to know in order
to select the right motor for my application?
What wattage motors do your Brushless
DC go up to?
How fast do your Brushless DC
go up to?
What type of value added work
does Shinano Kenshi Corporation provide?
How will the Speed/Torque curve
change if I supply higher voltage or more current?
How come your integrated connector
stepper motors are rated only at Class A for temperature?
What are the differences between
variable reluctance stepper motors and permanent magnet stepper motors?
How does demagnetization occur?
How does the counter EMF reduce
the motor torque?
How does demagnetization occur?
What is the conversion for oz-ins
of torque to gf-cm?
How will the Speed/Torque curve
change if I supply higher voltage or more current?
How come your integrated connector
stepper motors are rated only at Class A for temperature?
If I buy your integrated connector
stepper motor, does it come with a wire harness?
Does SKC make drivers for stepper
motors?
What new innovations are coming
out of SKC today?
Can you do MIL-Spec motors?
Are you ISO certified in Japan?
In China?
Can you provide me with a copy
of your ISO Certificate?
I need driver information.
At what quantities levels will
you do custom products?
What is Bifilar winding?
Where do the sources of heat
inside the motor come from?
What is MTTF vs. MTBF?
If I buy your integrated connector
stepper motor, does it come with a wire harness?
Will the part number change when
we make a custom motor?
Does
Shinano Kenshi Corporation make drivers for stepper motors?
What is the difference between Unipolar and
Bipolar?
A unipolar stepping motor has 5 or 6 lead wires usually with a center
tap on each of two windings. In use, the center tap of the windings
are typically wired to the positive supply, and the two ends of each
winding are alternately grounded to reverse the direction of the field
provided by that winding.
A bipolar motor is constructed with exactly the same
mechanism as is used on unipolar motors, but the two windings are wired
more simply, with no center tap. Thus, the motor itself is simpler but
the drive circuitry needed to reverse the polarity of each pair of motor
poles is more complex. (top)
What are the advantages of Micro stepping?
Micro stepping serves three purposes. First, it allows
a stepping motor to stop and hold a position between the full or half-step
positions. Second, it largely eliminates the jerky character of low
speed stepping motor operation and the noise at intermediate speeds.
Third, it reduces problems with resonance.
Although some micro stepping controllers offer hundreds
of intermediate positions between steps, it is worth noting that micro
stepping does not generally offer great precision, both because of linearity
problems and because of the effects of static friction. (top)
How do you control resonance in your application?
Use of elastometric motor mounts or elastometric couplings
between motor and load can drain energy out of the resonant system,
preventing energy from accumulating to the extent that it allows the
motor rotor to escape from control. This can help control resonance
in your application.
Also viscous damping can be used. Here, the damping
will not only draw energy out of the resonant modes of the system, but
it will also subtract from the total torque available at higher speeds.
Magnetic eddy current damping is equivalent to viscous damping for these
purposes. (top)
What do I need to know in order to select the
right motor for my application?
1. Driving condition: Voltage, speed, dynamic torque/inertia,
current, and duty cycle
2. Size constraint: Ambient temp and temp range, life of the motor
For steppers
1. Driving method: Constant current or constant voltage
2. Driving the motor: Unipolar or bipolar
For BLDC
1. Driving the motor: Constant speed or variable speed.
(top)
What wattage motors do your Brushless DC go
up to?
From 1 watt to 150 watts. (top)
How fast do your Brushless DC go up to?
Most are variable speed with ranges from 400-3000 rpm
while some models can run as high as 45,000 rpm. (top)
How will the Speed/Torque curve change if I supply higher
voltage or more current?
Higher supply voltage will result in higher speed capabilities;
more current will result in more torque. (top)
How come your integrated connector
stepper motors are rated only at Class A for temperature?
The limiting factor is the PC Board which is rated
for Class A. However all key internal components (windings, etc) are
UL listed as Class B. Data can be provided upon request. Shinano Kenshi
Corporation has the capability to supply high temperature rated motors
over NEMA 17 and 23 frame sizes. (top)
What are the differences between
variable reluctance stepper motors and permanent magnet stepper motors?
You can generally tell the two apart by simply feeling
them when no power is applied. Permanent magnet motors tend to "cog"
as you twist the rotor with your fingers, while variable reluctance
motors almost spin freely (although they may cog slightly because of
residual magnetization in the rotor). You can also distinguish between
the two varieties with an ohmmeter. Variable reluctance motors usually
have three (sometimes four) windings, with a common return, while permanent
magnet motors usually have two independent windings, with or without
center taps. Center-tapped windings are used in unipolar permanent magnet
motors
Stepping motors come in a wide range of angular resolution.
The coarsest motors typically turn 90 degrees per step, while high resolution
permanent magnet motors are commonly able to handle 1.8 or even 0.72
degrees per step. With an appropriate controller, most permanent magnet
and hybrid motors can be run in half-steps, and some controllers can
handle smaller fractional steps or microsteps. Hybrid motors are indistinguishable
from permanent magnet motors from the controller's point of view.
For both permanent magnet and variable reluctance stepping
motors, if just one winding of the motor is energized, the rotor (under
no load) will snap to a fixed angle and then hold that angle until the
torque exceeds the holding torque of the motor, at which point, the
rotor will turn, trying to hold at each successive equilibrium point.
(top)
How does demagnetization occur?
The best way to demagnetize something is to expose it to a high frequency-high
amplitude magnetic field. This can be accomplished by running the control
system to spin the rotor at high speed when the rotor is actually stalled,
or spinning the rotor at high speed against a control system trying
to hold the rotor in a fixed position. These will both expose the rotor
to a high amplitude high-frequency field. If such operating conditions
are common, particularly if the motor is run near the curie temperature
of the permanent magnets, demagnetization is a serious risk and the
field strengths (and expected torques) should be reduced accordingly!
(top)
How does the counter EMF reduce the
motor torque?
In a permanent magnet or hybrid stepping motor, the magnetic field of
the motor rotor changes with changes in shaft angle. The result of this
is that turning the motor rotor induces an AC voltage in each motor
winding. This is referred to as the counter EMF because the voltage
induced in each motor winding is always in phase with and counter to
the ideal waveform required to turn the motor in the same direction.
Both the frequency and amplitude of the counter EMF increase with rotor
speed, and therefore, counter EMF contributes to the decline in torque
with increased stepping rate. (top)
What is the conversion for oz-ins of
torque to gf-cm?
1 oz-in equals 72 gf-cm. (top)
How will the Speed/Torque
curve change if I supply higher voltage or more current?
Higher supply voltage will result in higher speed capabilities;
more current will result in more torque. (top)
How come your integrated
connector stepper motors are rated only at Class A for temperature?
The limiting factor is the PC Board which is rated
for Class A. However all key internal components (windings, etc) are
UL listed as Class B. Data can be provided upon request. SKC has the
capability to supply high temperature rated motors over Nema 17 and
23 frame sizes. (top)
If I buy your integrated
connector stepper motor, does it come with a wire harness?
As a standard motor, no. However, we can develop a
mating wire harness to match your needs (length, end termination in
your chosen connector, tubed wires, tie wrapped, etc.)
Does SKC make drivers
for stepper motors?
Not typically for OEM applications. We can recommend
the best drive methodology based on a review of your application and
design parameters. (top)
What new innovations are coming out of SKC
today?
Shinano Kenshi Corporation is constantly looking at
new technology and developing new products. To view our current innovations
please click here.
Can you do MIL-Spec motors?
No. (top)
Are you ISO certified
in Japan? In China?
Shinano Kenshi Corporation is ISO certified in both
our Japan and China locations. This ISO certification also readfiles
the ISO14000 and will eventually readfile the new TS16/7xxx certification.
(top)
Can you provide me
with a copy of your ISO Certificate?
Yes, please click here to get pdf file of ISO Certificates.
(top)
I need driver information.
Please view a list of highly qualified Driver manufacturers
here in the US. If you have questions about our drive designs for brushless
DC motors, please contact our Regional Sales Managers. (top)
At what quantities
levels will you do custom products?
This depends on many factors such as the complexity
of custom work and the overall volume a customer might expect for a
given product. Please contact your Regional Manager or Authorized Representative
for more details as these vary on a case-by-case basis. (top)
What is Bifilar winding?
Bifilar windings on a stepping motor are applied to
the same rotor and stator geometry as a bipolar motor, but instead of
winding each coil in the stator with a single wire, two wires are wound
in parallel with each other. As a result, the motor has eight wires
and not four. (top)
What are the sources of heat inside
the motor come from?
The heat given off by the motor windings is due to simple resistive
losses, eddy current losses, and hysteresis losses. If this heat is
not conducted away from the motor adequately, the motor windings will
overheat. The simplest failure which can be created is insulation breakdown,
but it can also heat a permanent magnet rotor to above its curie temperature,
the temperature at which permanent magnets lose their magnetization.
This is a particular risk with many modern high strength magnetic alloys.
(top)
What is MTTF vs. MTBF?
MTTF is defined as “Mean Time To Failure.” The point MTTF
is the total device hours divided by the number of failures. The failure
rate is defined as the reciprocal of the MTTF. Where no failures occurred
during testing, the point MTTF and failure rate have been calculated
assuming one failure. MTBF is defined as “Mean Time Between Failures”.
It is the average time a system will operate without a failure. Failure
may be the result of one or many faults. The MTBF is a commonly quoted
reliability in engineering. (top)
If I buy your integrated connector stepper
motor, does it come with a wire harness?
As a standard motor it does not. However, we can develop
a mating wire harness to match your needs (length, end termination in
your chosen connector, tubed wires, tie wrapped, etc.) (top)
Will the part number change when we
make a custom motor?
Yes, part numbers change and a new one will be issued for each custom
product and customer.
Does Shinano Kenshi Corporation make
drivers for stepper motors?
Not typically for OEM applications. We can recommend the best drive
methodology based on a review of your application and design parameters.
(top)
What are the advantages of Micro stepping?
Micro stepping serves three purposes. First, it allows a stepping motor
to stop and hold a position between the full or half-step positions.
Second, it largely eliminates the jerky character of low speed stepping
motor operation and the noise at intermediate speeds. Third, it reduces
problems with resonance. Although some micro stepping controllers offer
hundreds of intermediate positions between steps, it is worth noting
that micro stepping does not generally offer great precision, both because
of linearity problems and because of the effects of static friction.
(top)
How do you control resonance in your
application?
Use of elastometric motor mounts or elastometric couplings between motor
and load can drain energy out of the resonant system, preventing energy
from accumulating to the extent that it allows the motor rotor to escape
from control.
Or, viscous damping can be used. Here, the damping will not only draw
energy out of the resonant modes of the system, but it will also subtract
from the total torque available at higher speeds. Magnetic eddy current
damping is equivalent to viscous damping for our purposes. (top)
