PERFORMANCE
31
Motor torque is approximately proportional to motor current multiplied by the number
of winding turns that carry the current. In full-winding operation, twice the number of
turns carry current as in half-winding operation, so only half the current is needed to
generate a given level of torque. Unfortunately full-winding operation quadruples the
effective winding inductance. In Region 2, motor power is proportional to the inverse of
the square root of the winding inductance.
Figure 12 (Page 32) illustrates the effect of various winding currents on motor
performance. A 4 Amp per phase motor was driven from 1 to 6 Amps per phase in 1
Amp increments.
Note that if the motor in Figure 12 is operated in excess of 4000 steps/sec., the current
set resistor value would make no difference in performance. What would be significant
is the reduction in low speed heating of the motor and drive evident at the lower current
setting.
Figure 13 (page 32) illustrates the effects of full vs. half winding operation at low and
high power supply voltages. Note that full-winding operation at 54 VDC yields
performance virtually identical to half-winding operation at 27 VDC.
Full-winding configuration is preferred for Region 1 operation, and is suitable for
Region 2 if the power available is sufficient. The benefits are low motor and drive
heating and modest power supply current requirements. For full-winding operation the
phase current level of the CN0162 is set to one-half the motor's nameplate phase current
rating.
The half-winding configuration doubles high speed torque. Motor phase currents are
twice those in a full-winding connected motor. This doubles power supply requirements
and thus results in hotter motor and drive temperatures. For high performance operation
the phase current level of the CN0162 is set to the motor's nameplate phase current
rating.
Holding torque and low speed torque are the same in half-winding and
full-winding configurations.
