Quad Amp Hardware Reference Manual
Introduction
6

Protection

There are several layers of protection built into the amplifier, including transient voltage filters, transient
surge suppressors, fuses, a flyback diode, and a variety of fault detection circuits. These are discussed in
the following paragraphs and in the Troubleshooting Chapter.

Transient Voltage Filter

The transient voltage RC filter is used as a means of suppressing inductive transients and is located across
the single phase Control AC input voltage connector C3.

Transient Surge Suppressors

Transient surge suppressors (also referred to as metal oxide varistors or MOVs) are connected across all
three input phases (L1, L2, L3) of the Main AC input power. They are located on a circuit board attached
to the top of the bridge power rectifier. The primary function of these devices is to absorb high-level
energy pulses (spikes).

Fly-Back Diode

The fly-back diode clamps inductive spikes that may be generated across the external shunt resistors
when the shunt IGBT is turned off. The diode is connected across the external shunt resistor terminals.

Fuses

The primary hardware protection is fuses, which are mounted within the Quad Amplifier chassis.

Fuse F201

F201 is a 30 Amp long delay fuse, located externally on the top cover of the Quad Amplifier. Fuse F201
is connected to the output of the shunt regulator IGBT and to the internal shunt regulator resistors. Fuse
F201 protects the shunt regulator IGBT and the internal shunt resistors from over current damage.

Fuse F202

F202 is a 4-Amp Slo-Blo fuse located under the Quad Amplifier cover, next to the control AC input
power supply transformer. This fuse is connected between incoming AC control input power connector
C3 and control input AC power transformer T201. Fuse F202 protects the primary input windings of the
control power supply transformer against overloads.

Ground Fault (GF)

The Ground Fault Detector is a self-powered circuit that continuously samples the AC line currents via a
toroid around the incoming three phase lines. If there is more current flowing into the amplifier than out,
the ground fault circuit will activate and shut down the Quad Amplifier with a soft start fault.