QSH4218-41-10-035 TRINAMIC, QSH4218-41-10-035 Datasheet - Page 11

• Manufacturer Part Number: QSH4218-41-10-035
• Description: STEPPER MOTOR, 1.8DEG, 1A, 0.35NM
• Manufacturer: TRINAMIC

Specifications of QSH4218-41-10-035

• Torque Max: 10N-m
• No. Of Phases: 2
• Inductance: 7.5mH
• Inertia: 35g-cm2
• Current Per Phase: 1A
• External Depth: 42mm
• External Length / Height: 39.4mm
• External Width: 42mm
• Holding: RoHS Compliant
• Coil Type: Bipolar
• Svhc: No SVHC (15-Dec-2010)
• Rohs Compliant: Yes

QSH4218 Manual (V1.05/2009-JUN-20)
6.3.1
6.4
Within SI units, the numeric value of the BEMF constant has the same numeric value as the numeric
value of the torque constant. For example, a motor with a torque constant of 1 Nm/A would have a
BEMF constant of 1V/rad/s. Turning such a motor with 1 rps (1 rps = 1 revolution per second =
6.28 rad/s) generates a BEMF voltage of 6.28V.
The Back EMF constant can be calculated as:
The voltage is valid as RMS voltage per coil, thus the nominal current I
formula, since the nominal current assumes a full step position, with two coils switched on. The
torque is in unit [Nm] where 1Nm = 100cNm = 1000mNm.
One can easily measure the BEMF constant of a two phase stepper motor with a (digital) scope. One
just has to measure the voltage of one coil (one phase) when turning the axis of the motor manually.
With this, one gets a voltage (amplitude) and a frequency of a periodic voltage signal (sine wave).
The full step frequency is 4 times the frequency the measured sine wave.
Copyright © 2008, TRINAMIC Motion Control GmbH & Co. KG
Try to brake the motor and listen to it at different velocities. Does the sound of the motor get
raucous or harsh when exceeding some velocity? Then the motor gets into a resonance area. The
reason is that the motor back-EMF voltage reaches the supply voltage. Thus, the driver cannot bring
the full current into the motor any more. This is typically a sign, that the motor velocity should not
be further increased, because resonances and reduced current affect motor torque.
Measure the motor coil current at maximum desired velocity
For microstepping:
For Fullstepping:
If you determine, that the voltage is not sufficient, you could either increase the voltage or reduce
the current (and thus torque).
Back EMF (BEMF)
Determining if the given driver voltage is sufficient
U
BEMF

 
rad
V
/
If the waveform is still basically sinusoidal, the motor driver supply voltage is
sufficient.
If the motor current still reaches a constant plateau, the driver voltage is
sufficient.
s

 

MotorHoldi
2

I
NOM
ngTorque
 
A
 
Nm
NOM
is multiplied by 2 in this
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