Answer / suresh

due to low voltage less magnitic fied to rotate the motor
when we must rotate initially. no torque developed.
testing purpose ht motors run on lt supply through dimmer.

Answer / ketan verma

HT motor will rotate at a low speed if 415 v power supply
is given to the terminals of an ht motor. This a a type of
test in which if the moisture is found in the motor then
the same can be evaporated by this method. Moreover, there
is a test called block rotor test in which we can block the
rotor shaft and give the 415 v power supply to terminals
and thus the heating will occur in the winding and thus the
IR value will improve. This has been practically testes by
us at lot of sites....

Answer / mangesh mane

as supply is lv, motor torque will became low if it will
lower than minimun torque required to just rotate the
motor then motor will not run or rotate otherwise it will
rotate at lower speed than rated speed & motor current will
remain less than 6 times of its rated current

Answer / anand ahuja

If 415V 3-ph 50Hz power supply is connected to a motor which
is rated, say, 3.3kV or 6.6kV or 11kV, the motor will not
start at all as it will not develop sufficient magnetic
field and there it will not develop sufficient torque.
Basically, the number of turns in a HT motor are high
compared to the no. of turns in an LT motor. When LT
voltage is applied to HT motor, the voltage drop per turn or
the emf per turn is very low and thereby it does not develop
sufficient magnetic field.
In case of a star-delta start of normal LT induction motor,
the voltage applied (or potential applied) to the windings
is less in star connection than that in delta connection.
In case of LT motors, the current drawn is high on low
voltage being applied to it when it is within a certain
range. That is a 415V motor is connected to 380V or 320V
supply.
Whereas, applying 415V to a 3,300V or 6,600V or 11,000V
motor is similar to applying voltage as low as 20V to 40V to
415V motor.

Answer / v.v.raveendra

HT motor runs slowly.

Answer / s m mishra

No sufficient torque will develop.

Answer / vinodkumar

motor will not run or will run at low speed

Answer / balkishan gothwal

We can give 10% of HT voltage to LT motors for testing
without no nolad.Some time you may push to get in rotation
once if it picks speed it will be rotating with the same
speed as HT voltage provided the frequency will be
same.Because the speed depends on frequency not on voltage.
this is used for healthiness of motor by applying LT
voltage to HT motors.

Answer / a v subba rao

We can connect HT motor with LT supply in no load with out
any problem for site testing. Only thing motor will not
start due it will not devalop sufficient torque,but if we
rotate the shaft at the starting motor will start rotating
at lower speed first and it will slowly increse to up to
rated speed if we can not remove the supply. This test has
to be done only idle motor.

Answer / sameer vijayakar

motor will pick up the full speed slowl as the motor runs
on low torque and the inertia helps in pcking up speed as
the torque is consistently applied.

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