Stepper motors are available in many different models. One of the main differences is the number of connections. That can vary from 4 to 8 wires or terminals.
The oldest models, for the unipolar drives have 5 or 6 leads. The newest ones for the bipolar drives and do have only 4 leads.
Below is an overview of all possible stepper motor connections. If you find a motor with a number of wires not mentioned below then there is something wrong. If, for example a motor has 7 wires then there are two possibilities:
|8||As 6 or 5 lead motor||Serial or parallel connection|
|6||As 6 or 5 lead motor||Serial or One Winding|
|5||As 5 lead motor||Not possible|
|4||Not possible||Standard Connection|
The 5 and 6 leads motors are the oldest models. Their construction comes straight from the synchronous motor with two windings. The windings are split in the middle and connected to a powersupply. In most cases there was a current limeting resistor between the windings and the power supply. An example value is 4.5 Ohm for a 4 amp motor. These resistors were generating a lot of heat and they keep also the efficiency very low.
Almost all 6 leads motors can be connected to a bipolar drive, but the performance will be not at the maximum. However, when an old unipolar drive is replaced by a new bipolar one in general the performance will be better. Serial connection of the windings is basicly for high torque and low speed applications.
This special connection can be used when a 6 lead motor, with serial windings has a too high inductance. For an eight lead motor this is not a very common connection.
With the windings in parallel, the motor current can be higher whilt the inductance is lower. This is a typical connection for a motor that need to run at a high speed..
This is the standard connection for a bipolar drive. Please note that the motor seems to have only two windings, but this is not true. There are still four windings and, depending on motor type, they are in series or parallel. Most manufacturers makes two models with the same winding, but one time connected is series and one time in parallel.