AMS DCB-274 manual Amps and Wire Count and Power, Basic 8 Wire Motor

ADVANCED MICRO SYSTEMS, INC. ADDENDUM

AMPS and Wire Count and Power

The rated current is specified based on the rated power input (watts) of a given motor.

A. Basic 8 Wire Motor

While never actually used as 8 individual coils, virtually all permanent magnet motors have 4 internal coils. All common configurations can be constructed from the 8-wire motor.

Let us assume that each of 4 windings of the 8-wire motor has the following specifications:

Current = 1 amps

Resistance =2.0 ohm (each of 4 coils) Voltage= 2.0 volts

Inductance = 4.4 mH

The power per winding is:

I2R or 2 x 2 x 1= 4 watts,

x 4 coils = 16 watts total for this motor.

1

5

2

6

3 7 4 8

A Basic 8 Wire Motor

These values correspond closely with a NEMA size 23, 4 wire motor designs.

These following examples will configure the basic 8-wire motor into four real life connections:

1B	1
	5
	2
1A	6
	3	7	4	8
	2A			2B
	4 Wire Parallel

4 Wire Parallel

The high-speed model implements parallel coil connection. Two coils connected in parallel result in the following for each of the two phases:

Parallel Resistance= 1 ohms Parallel Inductance= 2.2 mH Current= 2.83 amps (8 watts/phase)

Watts per phase=8 (x 2 phases) = 16 watts total

B. 4 Wire Series

Changing to a series design, we have two pairs of two coils connected in series. Each has:

Series Resistance= 4 ohms Inductance= 17.5 mH

The rated current is now 1 amps (4 Volts) Watts per phase=8 (x 2 phases) = 16 watts total

Note that the series inductance is FOUR times the parallel design. Inductance limits the obtainable speed, since the time constant limits the amount of flux (hence torque) when step-to-step time is short.

1B 1

5

2

1A 6

3 7 4 8

2A 2B

4 Wire Series

6 3