but the results are only for one momentary service interruption duration using a 0.75 hp
unloaded motor. In 1979,  presents experimental data for the case of out of phase bus
transfer of a 111 hp induction motor, but only current transient data is provided. In 2001,
 investigated the effects of a momentary service interruption and a supply fault
disturbance on a 7.4 hp induction motor, but again, only current transient data is provided.
These are the only experimental studies that address induction motor behavio r during
momentary service interruptions, voltage sags, or supply vault disturbances. A closer look at
  and  follows.
In 1967, I.R. Smith, et al perform the first experimental torque transient analysis of a loaded
induction machine subjected to a momentary service interruption . The experimental data
is obtained from a 7.5 hp three-phase induction motor connected to a dc generator. To
measure shaft torque, strain gages are fastened to the motor shaft and fed into a transistor
amplifier through a set of slip rings. A momentary service interruption is generated by
manually switching off the supply voltage and then reconnecting it before the rotor stops
spinning. The authors call this process "reswitching". Fig 4 shows experimental and
analytical results of removing the supply voltage for 4.65 cycles. The analytical results are
computed using the dq0 reference frame model, as shown in Appendix A. Torque transient
peaks of 5.5 times full load torque (5.5 pu) and transient current peaks of 13 times rated
current (13 pu) are measured and match analytical results reasonably well. Although not
shown in Fig 4, tests are also performed where the supply voltage is reconnected at the
instant the back-emf and supply voltage are in phase. In this case, the magnitude of the
torque transients are significantly less than the magnitude of the transients seen in Fig 4.
This study clearly shows that torque and current transients are produced if a motor is allowed
to ride-through a momentary service interruption. The torque during this test actually
reverses direction, indicating that the shaft decelerates in order to realign the rotor field with
the stator circuit flux magnetic field. Unfortunately, the results of only one interruption
duration are published and tests are only conducted on one motor at full load.