Model 6210 Maintenance Manual
Section 5. Troubleshooting AC Electric Motors
AC Electric Motors AC Motor Type The traction motor is a brushless, 3-phase, variable speed AC motor. The AC motor has a rotor (in place of the DC armature) and a stator (in place of the DC field). There is no electrical connection to the rotor; current is induced in the rotor. The stator has three windings staggered 120° apart, and three external connections labeled U, V, and W. See Figure 5-3 and Figure 5-4. Figure 5-3.
AC Traction Motor circuit - Phase A
Figure 5-4.
AC Traction Motor circuit - Phase B
Shorted Winding If the AC motor fails with a shorted winding, the motor speed fluctuates up and down, as if hunting/searching, and there is a high-pitched sound. Using a clamping ammeter, measure current in each of the motor power cables. The shorted phase reads significantly higher than the other two phases.
Open Winding If the AC motor fails with an open winding, the motor moves erratically, as if hunting/searching, and there is a ticking sound. Rotation is much slower than normal. Using a clamping ammeter, measure current in each of the motor power cables. The open phase reads significantly lower than the other two phases.
Publication: 1146947, Revised: 12 Jan 2017
5-9
