ircon Modline 4, Installation And Operation Manual

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Appendix
A–1
NEMA SAFETY GUIDELINES FOR THE APPLICATION, INSTALLATION, AND
MAINTENANCE OF SOLID STATE CONTROL
Section 1: DEFINITIONS
(This section is classified as NEMA Standard 11-
15-1984.)
Electrical Noise —Unwanted electrical energy
which has the possibility of producing undesirable
effects in the control, its circuits, and system.
Electrical Noise Immunity —The extent to which
the control is protected from a stated electrical
noise.
Off-State Current —The current that flows in a
solid state device in the off-state condition.
Off-State Condition —The conditions of a solid
state device where no control signal is applied.
On-State Condition —The condition of a solid
state device when conducting.
Surge Current —A current exceeding the steady
state current for a short time duration, normally
described by its peak amplitude and time duration.
Transient Overvoltage —The peak voltage in
excess of steady state voltage for a short time dur-
ing the transient conditions (e.g., resulting from the
operations of a switching device).
Section 2: GENERAL
(
Sections 2 through 5 are classified as Authorized
Engineering Information 11-15-1984.)
Solid State and electro-mechanical controls can
perform similar control functions, but there are cer-
tain unique characteristics of solid state controls
which must be understood.
In the application, installation and maintenance of
solid state control, special consideration should be
given to the characteristics described in 2.1
through 2.7.
2.1 AMBIENT TEMPERATURE
Care should be taken not to exceed the ambient
temperature range specified by the manufacturer.
2.2 ELECTRICAL NOISE
Performance of solid state controls can be affected
by electrical noise. In general, complete systems
are designed with a degree of noise immunity.
Noise immunity can be determined with tests such
as described in 3.4.2. Manufacturer recommended
installation practices for reducing the effect of
noise should be followed.
2.3 OFF-STATE CURRENT
Solid state controls generally exhibit a small
amount of current flow when in the off-state condi-
tion. Precautions must be exercised to ensure
proper circuit performance and personnel safety.
The value of this current is available from the man-
ufacturer.
2.4 POLARITY
Incorrect polarity of applied voltages may damage
solid state controls. The correct polarity of solid
state controls should be observed.
2.5 RATE OF RISE–VOLTAGE OR CURRENT
DV/DT or DI/DT
Solid state controls can be affected by rapid
changes of voltage or current if the rate of rise
(DV/DT and/or DI/DT) is greater than the maximum
permissible value specified by the manufacturer.
2.6 SURGE CURRENT
Current of a value greater than that specified by
the manufacturer can affect the solid state control.
Current limiting means may be required.
2.7 TRANSIENT OVERVOLTAGE
Solid state controls may be affected by transient
over-voltages which are in excess of those speci-
fied by the manufacturer. Voltage limiting means
should be considered and may be required.