OPERATION
Copyright
Trace Engineering Company, Inc.
5916 - 195th Street N. E.
Arlington, WA 98223
Telephone: 360/435-8826
Fax: 360/435-2229
www.traceengineering.com
SW Series Inverter/Charger
Part No. 2031-5
Rev. B: Sept 1, 1999
Page
89
NORM.
OPEN
RELA
SOLAR ARRAY
+P -N
120VAC
COIL
+P -N
BATTERY BANK
SW - SERIES
INVERTER
AUX RELAY 9 COM.
AUX RELAY 9 N.C.
5 AMP
FUSE
-N
+P
AC OUTPUT - NEU
AC OUTPUT - HOT
OVERVOLTAGE PROTECTION FOR THE BATTERY IN SELL MODE
Normally, the inverter will regulate the charging process of the battery by selling excess power into the
utility grid. The battery will receive a three-stage charge routine as previously described. If the utility grid is
not available (due to an outage or tripped AC input circuit breaker, etc.) or if the inverter shuts off, then the
inverter is not able to sell the excess power and the battery voltage will not be regulated, resulting in
possible overcharging of the battery.
Therefore, a separate control is required to provide overvoltage protection for the battery when an outage
has occurred. The Aux Relays in the SW Series Inverter/Charger are designed to control an externally
connected power relay that would disconnect the solar array and stop the charging process. The voltage
and hysteresis (difference between opening and closing voltage) are both adjustable. The external relay
can be either a standard mechanical type or a mercury displacement type, depending on the voltage and
current required. The mercury displacement type relay is usually required when the system voltage is 48
VDC or if the current of the solar array exceeds about 20 amps. Multiple relays can be used if the solar
array is divided into several source circuits (do not parallel relays for higher current). Another option is to
use a charge controller such as the Trace C40. For more on the C40 MULTI-FUNCTION CONTROLLER,
see page 129.
A typically wiring configuration for this overvoltage protection is as follows:
This circuit does draw a small amount of power all of the time to power the coil of
the relay. Other circuits are possible but may have other drawbacks. This circuit
provides protection against overcharging the batteries.
Figure 30, Overvoltage Protection for Battery
AUX RELAYS
Three voltage-controlled relays are provided to simplify installations that have battery voltage related tasks
to perform. They are single pole double throw, five amp relays. Both the normally closed and normally
open contacts are available for each relay. The operation of the relays are individually controlled and
adjustable via the user menu. The battery voltage at which each of these relays are activated (SET
RELAY 9, 10 or 11 VOLTS DC) and the number of volts by which the battery voltage must drop before
the relay is de-activated (R9, R10 or R11 HYSTERESIS VOLTS DC) are both individually adjusted for
each relay. The three Aux Relays operate independently of the inverter or charger. For location and wiring
information on the Aux Relays, see the AUXILIARY AND GENERATOR CONTROL RELAY section on
page 14.
CAUTION: These relays are not intended to directly control a load or charging source - rather they can be
used to send a signal or operate the coil of another higher amperage device which does the actual
switching of the power. A fuse rated at 5 amps or less should be included to protect each of the relays.
Damage to these relays from overloading is not covered by warranty and requires the inverter to be
returned to a repair center. This also applies to the generator control relays.
Summary of Contents for SW II - REV 4.01
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