Applied Motion ST10-C-CE - Manual (Page 36)

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ST5/10-Si,-Q,-C, -IP Hardware manual 920-0004 Rev. F
6/10/14
drive’s maximum input voltage specification.
Current
The maximum supply current you could ever need is the sum of the two phase currents. However, you will
generally need a lot less than that, depending on the motor type, voltage, speed and load conditions. That’s
because the ST drives use switching amplifiers, converting a high voltage and low current into lower voltage
and higher current. The more the power supply voltage exceeds the motor voltage, the less current you’ll
need from the power supply. A motor running from a 48 volt supply can be expected to draw only half the
supply current that it would with a 24 volt supply.
We recommend the following selection procedure:
1. If you plan to use only a few drives, get a power supply with at least twice the rated phase current of
the motor.
2. If you are designing for mass production and must minimize cost, get one power supply with more
than twice the rated current of the motor. Install the motor in the application and monitor the current
coming out of the power supply and into the drive at various motor loads. This will tell you how much
current you really need so you can design in a lower cost power supply.
Choosing a Power Supply
When choosing a power supply, there are many things to consider. If you are manufacturing equipment that
will be sold to others, you probably want a supply with all the safety agency approvals. If size and weight
are an issue use a switching supply.
You must also decide what size of power supply (in terms of voltage and current) is needed for your applica-
tion.
Voltage
PWM drives work by switching the voltage to the motor terminals on and off while monitoring current to
achieve a precise level of phase current. To do this efficiently and silently, you’ll want to have a power
supply with a voltage rating at least five times that of the motor. Depending on how fast you want to run the
motor, you may need even more voltage than that.
If you choose an unregulated power supply, make sure the no load voltage of the supply does not exceed the