A growler is an

electrical Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...

device primarily used for testing a

motor An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power g ...

for shorted coils. A growler consists of a coil of wire wrapped around an iron core and connected to a source of

alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...

. When placed on the armature or stator core of a motor the growler acts as the primary of a

transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...

and the armature coils act as the secondary. A "feeler", a thin strip of steel (hacksaw blade) can be used as the short detector.

Motor testing

The alternating magnetic flux set up by the growler passes through the windings of the armature coil, generating an alternating voltage in the coil. A short in the coil creates a closed circuit that will act like the secondary coil of a transformer, with the growler acting like the primary coil. This will induce an alternating current in the shorted armature that will in turn cause an alternating magnetic field to encircle the shorted armature coil. A flat, broad, flexible piece of metal containing iron is used to detect the magnetic field generated by a shorted armature. A hacksaw blade is commonly used as a feeler. The alternating magnetic field induced by a shorted armature is strong at the surface of the armature, and when the feeler is lightly touched to the iron core of an armature winding, small currents are induced in the feeler that generate a third alternating magnetic field surrounding the feeler. With the growler energized, the feeler is moved from slot to slot. When the feeler is moved over a slot containing the shorted coil, the alternating magnetic field will alternately attract and release the feeler, causing it to vibrate in synch with the alternating current. A strong vibration of the feeler accompanied by a growling noise indicated that the coil is shorted.

Other uses

Along with the standard application the growler can be used: * to test

series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used in ...

and interpoles (commutating) fields from a DC motor * to determine phasing and polarity in multiwinding armatures * to test

rotor Rotor may refer to: Science and technology Engineering * Rotor (electric), the non-stationary part of an alternator or electric motor, operating with a stationary element so called the stator *Helicopter rotor, the rotary wing(s) of a rotorcraft ...

s in rotating frequency changers, as well as in wound rotors * to test shorts between turns in taped coils before installation into an armature or a stator * as a low voltage isolation

* as a high voltage

autotransformer An autotransformer is an electrical transformer with only one winding. The " auto" (Greek for "self") prefix refers to the single coil acting alone, not to any kind of automatic mechanism. In an autotransformer, portions of the same winding act a ...

bucking or boosting for numerous tests on various types of equipment * for preheating or baking armatures and rotors.

References

* * {{Authority control Electrical test equipment Electric transformers Tools Electric motors