I am told that because of the high winding inductance of the motor, the PSU will not have enough power to drive these motors.
An important parameter in the selection or design of the driver is the current it sends through the coils of the motor.
The current specified for the motor is the maximum current that is allowable per phase. To avoid damage to the
motor it is decisive to ensure that this current is not exceeded. This implies that the current of the drive must be
restricted to this or any lower value. Many drives allow limiting the current either by potentiometer, DIP switches or
by soft setting for example through the indexer. As step motors tend to run hot it is advisable to use a current that is
as low as possible while still maintaining reliable operation of the application. This means that in many applications
the actual maximum phase current used will be lower than that allowed by the motor manufacturer. This will help to
maximize the lifetime of motor and driver hardware.
The higher the output voltage from the driver, the higher is the level of torque versus speed. You can think of the
voltage as the driver of the current. The higher the voltage, the faster will the current in the windings reach its new
target value from one step to the next. Therefore it is conceivable why a higher voltage will result in better speed
performance.
The torque versus speed behavior varies strongly across stepping motors. Parameters such as the inductance of
the coils and their resistance play an important role. The higher the inductance, the worse the performance will be at
higher speeds.
The voltage applied to the step motor should be higher than the rated motor voltage. It is common to use a voltage
that is 3 to 25 times the rated motor voltage. As an example, for a motor that is rated at 3.7V, supply voltages in the
range of 11V to 92V are typical. Again, the higher the voltage, the better the performance will be.
Note that the rated motor voltage does not represent the maximum voltage that can be applied to the motor. In fact,
the motor will normally not operate properly at the rated motor voltage.
Unregulated power supplies are best suited for step motor applications.
The current capability is another key parameter in selecting an appropriate power supply. The current rating is
determined by the choice of motor and the stepping mode you are planning to use it in. Full step mode, where both
phases are on all the time at maximum current, requires more current than microstepping modes. Also, the current
draw strongly depends on the voltage. The higher the voltage, the less current will be required from the power
supply to achieve a given phase current in the windings of the motor.
Typically a power supply capable of delivering ½ or more of the peak phase current should be sufficient. For
example, if you are using a motor with a maximum phase current of 4A per phase and assuming the drive is set to
this maximum value, a power supply capable of delivering 2A or more will be adequate in most applications.
When connecting several drives / motors to one power supply, the current draw for all drives need to be added
together to yield the requirement for the power supply.
Your motor inductance/phase is 60mH >> this is high value >> for higher speeds motor needs higher voltage
- high supply voltage needs active current control in driver stage. ( series resistor only is not good enough in this case )
- On the other hand , motor in holding state (stopped) current should not be over 0.4A >> motor voltage = 12Vdc
Depending on the motor driver and needed max. speed motor supply voltage can be in range 24....48Vdc and even higher ??
Your motor current/phase is 0.4A >> so for 3 motors needed power supply current is 1.2...2.0A
quotations from : Stepper Motor System Basics (Rev. 5/2010)
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