Trinamic QSH5718-51-28-101 - 57 x 57mm 2-Phase Stepper Motor, 1.8 Degree, 1.01Nm, 0 - 75Vdc, 2.8A 50-0035 Fiche De Données
Codes de produits
50-0035
QSH5718 Manual (V2.3/2011-APR-12)
13
Copyright © 2011, TRINAMIC Motion Control GmbH & Co. KG
6.3.1 Determining if the given driver voltage is sufficient
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: If the waveform is still basically sinusoidal, the motor driver supply voltage is
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: If the waveform is still basically sinusoidal, the motor driver supply voltage is
sufficient.
For Fullstepping:
If the motor current still reaches a constant plateau, the driver voltage is sufficient.
If you determine, that the voltage is not sufficient, you could either increase the voltage or reduce the
current (and thus torque).
6.4 Back EMF (BEMF)
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:
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
NOM
is multiplied by 2 in this 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.
[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.
A
I
Nm
ngTorque
MotorHoldi
s
rad
V
U
NOM
BEMF
2
/