Applied Motion ST10-Plus - Manual (Page 20)

20
ST5/10-S Hardware manual 920-0027 Rev. D
2/7/14
Current
The maximum supply current you could ever need is the sum of the two phase currents. However, you will gener-
ally 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.
Recommended Power Supplies
Applied Motion Products offers two Power Supplies recommended for use with the ST drives. These are switch-
ing power supplies offering 24V and 48V, and an overload current capability making them ideal for use with drive
applications.
Model Power Output Voltage
PS150A24 150W 24VDC
PS320A48 320W 48VDC
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 application.
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
drive’s maximum input voltage specification.