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10
Overload, Short-Circuit & Ground-Fault Protection
In the USA, The National Electrical Code, NFPA 70, and all applicable local codes, govern how
to properly size, select and install overload protection (sometimes called heaters) and short-
circuit and ground-fault protection (fuses or circuit breakers). Proper selection and installation
of these devices is required and essential for not only protection of the electric vibrator and the
power supply circuit but also for protection of personnel.
If the overload or short-circuit and ground fault protection operate, have qualified personnel
locate and fix the problem before resetting.
When operating two electric vibrators, the vibrators should be controlled with a single motor
starter that has overload protection dedicated to each electric vibrator. The overloads shall be
electrically interlocked such that should there be a fault with one electric vibrator, both electric
vibrators will be de-energized.
Variable Frequency Inverter
The electric vibrators may be supplied with a variable frequency inverter. Never operate the
vibrators above the maximum frequency noted on the nameplate. If operating two vibrators,
use one variable frequency inverter along with overload protection dedicated to each electric
vibrator. The overloads shall be electrically interlocked such that should there be a fault with
one electric vibrator, both electric vibrators will be de-energized.
The nameplate current should never be exceeded throughout the entire frequency range.
Figure 9.
Ground Bonding Screw
Grounding & Bonding Cont.