PGA-016A Littelfuse Inc, PGA-016A Datasheet - Page 50

• Manufacturer Part Number: PGA-016A
• Description: BULK / WATERTIGHT COVER FOR PGR-6200 / PGR-7200
• Manufacturer: Littelfuse Inc

Specifications of PGA-016A

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

P
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applications attempting to spin the motor backwards will
result in damage to the load. An example of this is certain
impeller designs in downhole pumps.
Solution: Modern motor protection relays use digital
signal analysis to measure true-sequence components.
These sequence components are used for thermal model
calculations and take the extra heating into consideration.
Voltage unbalance which drives current unbalance can be
used as a start inhibit. Sequence components are also used
for calculating unbalance, phase loss and phase reversal.
Motor Jogging
NEMA designed motors are rated for two starts from cold and
one start from hot per hour. Motor jogging refers to excessive
starts and can cause overheating. The motor may not get up to
full speed and the forced air cooling is not effective.
Solution: Since the thermal model accurately tracks the
motor’s used thermal capacity at all times, including during
starts and between starts, the starts-per-hour feature may
not be required.
It is included for compatibility with protection relays that do
not have dynamic thermal-modeling capability.
Motor protection and the NEC
The NEC
devices against excessive heating due to overload and failure
to start (NFPA70 430 Section III).
NFPA 70 430, Part IV also specifies the use of devices
to protect against overcurrents such as short circuits
and grounds. Both of these NEC
many additional functions can be met with the use of a
multifunction motor-protection relay.
NFPA 70 430.32 (A)(4) requires the use of a protection
device having embedded temperature detectors that cause
current to the motor to be interrupted when the motor
attains a temperature rise greater than marked on the
nameplate in an ambient temperature of 40°C for motors
larger than 1500 hp.
The NEC
to provide protection from fire. Protection relays can provide
many enhancements to a facility above simple fire protection.
Communications
Network communications can be added to a motor protection
relay to allow remote metering of currents, voltages and
temperatures. Datalogging is a useful feature for troubleshooting
and comparing event sequences with process stages. Analysis
of information can often show operational issues.
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defines minimum requirements and is intended
requires the motor be protected by overload
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requirements and
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POWR-GARD
Motor Protection & Supplemental Monitoring
48
Supplemental Monitoring
Monitors are single function devices that only look at one
abnormal condition and either alarm or provide a means to
remove power. Visual indication can also be used. The purpose
of a monitor is to provide a low-cost solution to a dedicated
problem. Monitors are typically added to existing protection,
such as fuses, circuit breakers, or protection relays.
Insulation Monitors
The single most common reason for electrical system
failure is insulation breakdown. Insulation monitors can be
installed at any point in the system to detect a problem with
the insulation. The monitor is connected to one phase and
injects a dc signal to continuously measure the system’s
insulation resistance. The monitor is typically installed
on de-energized feeders or motors and is cycled with
feeder’s circuit breaker or motor starter. When the circuit
breaker is open, the monitor is energized and begins to
monitor the de-energized cables and motor windings. In
ungrounded systems, the monitor will continuously monitor
the insulation resistance to ground regardless whether the
system is energized or de-energized.
Ground Continuity Monitors
Ground check monitors are used to detect problems in
equipment ground conductors. Mobile equipment typically
has an extra wire, or pilot wire, routed with the phase
conductors. A monitor uses this pilot wire to send a signal
down to the equipment to a terminating device, where the
signal is sent back on the equipment ground conductor to the
monitor. The monitor continuously monitors this loop for open
or short circuits, indicating that a problem has occurred. The
monitor provides an alarm for this condition.
As an example, portable loads are grounded via single or
multiple conductors in a trailing cable. A ground fault on a
portable load will cause fault current to flow through the
ground conductors and all other ground-return paths. A
hazardous touch voltage can develop when the ground
conductor opens and a ground fault develops, assuming there
is not enough current to trip a ground-fault relay. If the portable
equipment has rubber tires or is not in good contact with
earth, then the next person to touch the equipment under fault
conditions will become part of the ground-return path.
Resistor Monitors
As discussed in the resistance grounded systems section, a
failure in the neutral to ground path will lead to a dangerous
situation. Some examples of failure are stolen wires, loose
connections, corrosion and broken resistor elements.
The resistor monitor continuously monitors the path from
system neutral to ground for a problem. When a problem
occurs, the monitor provides an alarm.
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Protection Relays
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