Rockwell Automation 810 5.0: Inverse Time Current Relays - Manual

INSTRUCTIONS
I
BULLETIN
810
INVERSE TIME CURRENT RELAYS
IMPORTANT - Save for future
reference.
Bulletin 810 rela
with a maximu
continuous
of 60 amperes.
OPERATING
FLUID
PISTON
COIL
CORE
DASHPOT
SILICONE
Cross sectional view.
Moving parts are shaded.
DESCRIPTION -The Bulletin 810 is a
magnetically operated current relay,
with time delay, for use on AC or DC
applications. It has inverse time-current
characteristics which are dependent.
upon the viscosity of the fluid in the
dashpot. However, unlike thermal re-
lays, minimum operating current is inde-
pendent of ambient temperature change
or cumulative heating. The relays are
supplied as standard with
a normally
closed (NC) contact and an automatic
reset. Available options are a normally
open (NO) contact, hand reset, and
bifurcated contacts with a clear plastic
(poly-carbonate) cover. Tripping current
and time delay are adjustable.
TIME DELAY TRIP - Current relays are
used when it is desirable to take a motor
off the line in a certain period of time after
a predetermined load condition is
reached. A typical application would be
starting a large motor, where the Bulletin
810 is used to automatically open the
motor starter control circuit if the motor is
CONTACT RATINGS -
AC DC
Maximum Contact Rating Per Pole
NEMA Rating Designation A600
M a x A C
Voltage
V o l t a g e Carrying
Continuous
Volt-amperes
Ampere
Amperes Range Rating
6 0 o r 5 0 Hz Make Break Current Make Break
120
240 6
3
7200 7 2 0 1 1 5 - 1 2 5
7200 7 2 0 2 3 0 - 2 5 0
00.4
0.2
480 1.5 10 7200 7 2 0 5 5 0 - 6 0 0 0.1
600 12 1.2 10
7200
720 I
not up to speed in the maximum accel-
eration time allowed. In this and other
applications of the automatic reset type
relay, three wire control must be used,
with a provision for interrupting the cur-
rent through the relay coil immediately
after the relay trips (see typical schema-
tic diagram on page 3 ). On two wire con-
trol applications such as float switches,
pressure switches or thermostats, a
hand reset type overload relay must be
used to provide this protection to the coil.
The relay can carry its rated continuous
current in the non-tripped position only.
OPERATION - Current through the Bul-
letin 810 operating coil imparts an elec-
tromagnetic force on the movable core.
The vertical position of the core in the
coil is adjustable, thereby providing an
adjustable trip point. When the coil cur-
rent increases to the trip point, the core
raises to operate the contact mecha-
nism. Time delay is provided by a sili-
cone fluid dashpot
mounted below the
core and coil assembly. An adjustable
valve in the dashpot piston provides for
time delay adjustment.
piston reaches an increased diameter in
the dashpot, where it is free, to trip the
contact with a quick action. Time and
current required to complete this cycle
are inversely related as shown by the
time-current characteristics curves on
page
2 .
RESET - Standard models of the Bulle-
tin 810 are automatically reset as soon
as the current through the coil is inter-
rupted or decreased to approximately
20% of the tripping current. The core is
designed to drop quickly, returning the
contacts to their normal position. A
check valve allows the piston to bypass
the fluid in its return to the bottom of the
dashpot. The action of hand reset mod-
els differs only in that the contacts do not
reset until a lever on the contact block is
operated. There is no waiting period as
with thermal relays.
NORMAL CURRENT - The electro-
magnetic force caused by normal con-
tinuous current through the operating
coil is not great enough to lift the core
and piston. The relay remains
inoperative.
OVERCURRENT - When the current
through the operating coil increases
beyond the trip point, the resultant elec-
tromagnetic force causes the core and
piston to raise. Upward motion is damp-
ened through the use of the silicone fluid
dashpot The core rises slowly until the
EFFECTS OF AMBIENT TEMPERATURE
- The minimum operating current
(100% on the time-current characteris-
tics graph) is independent of ambient
temperature at the relay. However, the
operating time at overcurrent varies
directly to the viscosity of the silicone
fluid. Since the viscosity varies inversely
with ambient temperature, the operating
time is also inversely affected. The time
temperature table shows the correction
factors to be applied to the operating
times for various temperatures.
TIME TEMPERATURE RELATIONSHIP
( + Reference) -
A m b i e n t
Temperature
Operating Time
Correction Factor
2.25 1.80 1.45 1.20 1.0
Publication 810-5.0 - April, 1983
Supersedes Publication 810-5.0, Dated December, 1980