Baker D30R, User'S Manual & Operating Instructions

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D30R Users Manual
66
Do Not Touch Test Leads while test is in Progress!
71-023 Rev C 5/8/2007
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Inverter drive transients.
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Line surges
caused by other motors or transformers tripping in the
power system.
One of the primary functions of a Baker Tester is to closely simulate the
transient voltages seen by the motor without the high energy that accompanies
the normally occurring transients. These spikes are a significant aging factor for
the end turn insulation of an electric motor.
Contact Bounce
Oddly enough one of the major sources for the high-energy transients is the
MCC, a device that is supposed to protect the motor. When the breaker contacts
close in the MCC during startup, they will often “bounce” or chatter, this means
that the high inrush current is being made and broken several times. As a result
of interrupting the current, an inductive “kick back” voltage spike will be
developed. Large inrush currents along with the high inductance of electric
motors are what give these “kick back” voltage spikes their high energy.
Lightening Strikes
Lightening strikes can often be present on the power system or grid. Although a
great amount of effort is made to protect the grid from the damage caused by
lightening, the high voltage transients caused by strikes still get through to
motors.
Inverter Transients
Variable speed drives or pulse width modulated drives are based on switching
currents very quickly in such a manner that the motor runs at a pre-set speed.
The switching of the current combined with the obvious fact that the motor is an
inductor result in high-speed transients being generated by the motor drive
electronics. These transients are impressed on the motor where they can slowly
degrade the insulation in the motor windings.
Line Surges
When a transformer or motor operating on a power system trips off line, the
energy stored in the motor or transformer has to go somewhere. The energy is
either absorbed by the device or is pushed out onto the power system where
other transformers or motors have to absorb the energy. Often, large transient