Bimba STP-10 - Manual (Page 27)

STP-10 Hardware Manual
27
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.
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 STP 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.