Hiwin IM-2-13, Инструкция по сборке

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Assembly Instruction Configuration
Torque Motor TM-Komponenten-04-0-EN-2108-MA Page 27 of 84
3.4 Power supply and controller selection
The continuous current, peak current and bus voltage must be considered while selecting a power supply. In
addition, the resonance effect which can be induced in motors by some drive systems must be taken into
account. Motors are assembled with several individual coils connected in series. Each one of these coils has an
inductance in series and a stray capacitance to earth. The LC network obtained possesses a resonant frequency,
so when an electrical oscillation is applied to the phase inputs (in particular the PWM frequency), the neutral
point of the motor can oscillate with very high amplitudes with respect to earth, and the insulation can be
damaged as a consequence of these oscillations. This phenomenon is more pronounced in motors with a large
number of poles (such as torque motors).
Under ideal conditions, the 600
V
DC
bus voltage generated by the power supply should be ± 300
V
DC
relative to
earth. However, in some configurations, the voltage between the buses and earth will have an oscillating voltage,
and the peak of the high voltage will be transmitted to the motor. The oscillation between voltage and earth
depends on system characteristics. By experience, a system with few axes connected to the bus voltage is less
liable to have disturbing oscillations on the bus, but for example in a large machine tool with many axes and
several spindles, the oscillations can reach high amplitudes. If the frequency of these oscillations is close to the
resonant frequency of the motor, it can lead to over-voltage failures on the neutral point.
The case where the PWM frequency of the controller happens to correspond to the resonant frequency of the
motor. In this case, the fundamental harmonic of the PWM frequency is directly exciting the resonant frequency
of the motor, and very high voltages are thus obtained on the neutral point. Also, as the PWM voltage is a square
wave, it contains odd harmonics (1, 3, 5, 7, etc.) that can also excite the motor resonance. Fortunately, these
harmonics have a smaller amplitude that the fundamental.
In another case, it may also lead an over-voltage failure. In this case, the fundamental harmonic of the PWM
frequency is directly exciting the resonant frequency of the motor, and very high voltages are thus obtained on
the neutral point. In addition, because the PWM voltage is a square wave, it contains odd harmonics (1, 3, 5, 7,
etc.) that can also excite motor resonance.
In conclusion, to prevent any failure from occurring, two elements must be considered: the oscillations between
the bus voltage and earth and the PWM frequency. If both elements above do not enter into resonance with the
motor, then there is no risk for the motor.
When selecting power supply, please check the conditions below:
Peak voltages and dV⁄dt gradients generated by the power supply must not exceed the values below:

300
V
DC
controllers: 750
V
p
(phase to ground), voltage gradient: 8kV/μs.

600 or 750
V
DC
controllers: 800
V
p
maximum (at the PWM frequency) and spikes up to 1.400 V (earth to
peak and for a few μs) and a voltage gradient: 11 kV/μs.
The cable between the controller and the motor will generate a reflected wave due to the impedance mismatch
between the cable and the motor, and the reflected voltage will be superimposed with the subsequent input
voltage, causing the voltage to rise. This phenomenon will be more obvious when the motor cable is longer. If the
length of the cable between the controller and the motor is longer than 10 m, it is necessary to measure
voltages at the motor terminals to ensure they are lower than specified above. If the measured value is greater, a
dV⁄dt filter must be inserted between the controller and the motor for protection.