National Electrical Code Procedures
Use the NEC motor current tables to find the design Full Load Current or FLA (adjusted for Service Factor) unless it is not available.
C For Single Phase Motors: Use NEC Table 430-148
C For Three Phase Motors: Use NEC Table 430-150
• These values are about 10% higher than what a typical motor would draw at full load to allow for bearing wear in the motor and load, etc.
C The values in the NEC tables will allow for replacement of the motor in the future without having to replace the circuit conductors or overcurrent devices.
Types of Overcurrent Devices - NEC TABLE 430-152
Selection of the size of the overcurrent protection device is made using NEC Table 430-152 which lists information for four types of devices:
1) Standard (non-time delay) Fuses 2) Time-Delay (dual element) Fuses
3) Instantaneous Trip Circuit Breaker 4) Inverse Time Circuit Breaker
• The table is used to size the device above normal starting current levels of most motors allowing them to start and run without tripping the overcurrent protection device.

Coils and Phases
A stepper motor may have any number of coils. But these are connected in groups called "phases". All the coils in a phase are energized together.

Unipolar vs. Bipolar
Unipolar drivers, always energize the phases in the same way. One lead, the "common" lead, will always be negative.
The other lead will always be positive. Unipolar drivers can be implemented with simple transistor circuitry. Thedisadvantage is that there is less available torque because only half of the coils can be energized at a time.
Bipolar drivers use H-bridge circuitry to actually reverse the current flow through the phases. By energizing the phaseswith alternating the polarity, all the coils can be put to work turning the motor.
A two phase bipolar motor has 2 groups of coils. A 4 phase unipolar motor has 4. A 2-phase bipolar motor will have 4wires - 2 for each phase. Some motors come with flexible wiring that allows you to run the motor as either bipolar orunipolar.

OTHER SUPERIOR PRODUCTS