6
Figure 8: 8-lead motor series connections
Parallel Connections
An 8 lead motor in a parallel configuration offers a more stable, but lower torque at lower speeds. But because of the
lower inductance, there will be higher torque at higher speeds. Multiply the per phase (or unipolar) current rating by
1.96, or the bipolar current rating by 1.4, to determine the peak output current.
6.
Power Supply Selection
Figure 9: 8-lead motor parallel connections
The DM860 can match medium and small size stepping motors (from NEMA frame size 17 to 34) made by many
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 driver. 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-driver 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 driver 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 Therefore, the average current withdrawn from power supply is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 Drivers
It is recommended to have multiple drivers 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 drivers. (Instead, please connect
them to power supply separately.)
