EM Series Drive Hardware Installation Manual
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HWMN-EM-R20111018
7. Power Supply Selection
The DM drive can match medium and small size stepping motors (from NEMA frame size 8 to 34) made by Leadshine or other motor
manufactures around the world. To achieve good driving performances, it is important to select supply voltage and output current
properly. Generally speaking, supply voltage determines the high speed performance of the motor, while output current determines the
output torque of the driven motor (particularly at lower speed). Higher supply voltage will allow higher motor speed to be achieved, at
the price of more noise and heating. If the motion speed requirement is low, it’s better to use lower supply voltage to decrease noise,
heating and improve reliability.
Regulated or Unregulated Power Supply
Both regulated and unregulated power supplies can be used to supply the drive. However, unregulated power supplies are preferred due
to their ability to withstand current surge. If regulated power supplies (such as most switching supplies.) are indeed used, it is important
to have large current output rating to avoid problems like current clamp, for example using 4A supply for 3A motor-drive operation. On
the other hand, if unregulated supply is used, one may use a power supply of lower current rating than that of motor (typically 50%
～
70% of motor current). The reason is that the drive draws current from the power supply capacitor of the unregulated supply only during
the ON duration of the PWM cycle, but not during the OFF duration. Therefore, the average current withdrawn from power supply is
considerably less than motor current. For example, two 3A motors can be well supplied by one power supply of 4A rating.
Multiple Drives
It is recommended to have multiple drives to share one power supply to reduce cost, if the supply has enough capacity. To avoid cross
interference, DO NOT daisy-chain the power supply input pins of the drives. Instead, please connect them to power supply separately.
Selecting Supply Voltage
The power MOSFETS inside the EM drive can actually operate with wider voltage range than the input specification. Higher supply
voltage can increase motor torque at higher speeds, thus helpful for avoiding losing steps. However, higher voltage may cause bigger
motor vibration at lower speed, and it may also cause over-voltage protection or even drive damage. Therefore, it is suggested to choose
only sufficiently high supply voltage for intended applications, and it is suggested to use power supplies with theoretical output voltage
of drive’s m 10% to drive’s maximum – 10%, leaving room for power fluctuation and back-EMF.
Driver Input Voltage
Driver Upper Input limit
Power Supply Voltage
Heating
Vibration
Maximum Safe Rating
Driver Upper Input limit
– 10%
Driver Lower Input limit
+ 10%
Driver Lower Input limit
Minimum Safe Rating
Torque
Speed
Safe Region
Driver Input Voltage
Driver Upper Input limit
Power Supply Voltage
Heating
Vibration
Maximum Safe Rating
Driver Upper Input limit
– 10%
Driver Lower Input limit
+ 10%
Driver Lower Input limit
Minimum Safe Rating
Torque
Speed
Safe Region
