Emergency Relay Circuit; General - Kubota WSM J Series Workshop Manual

J SERIES, WSM
come from the separate excitation unit (14). Let's take an example of a car engine. The separate excitation unit (14)
is equivalent to a fuel cut-off solenoid valve. With this unit running, the valve stays fully open. The rpm is controlled
by a governor, to which the drive circuit (5) is equivalent. Once the fuel cut-off solenoid valve gets closed, the engine
stops. In the same way, if the separate excitation unit (14) is not connected (no battery voltage applied), the generator
is interrupted.
(5) Transistor
As discussed in "Drive circuit (5)" the transistor is designed to switch on and off the rotor current and to adjust the
generator's output voltage. On the J Series A.V.R.s, the transistor is located projected from the mold with the heat
sink.
(6) Separate excitation unit
Just about half of the separate excitation unit's (14) function was already explained in "Drive circuit (5)". This
component serves also to feed power to the rotor when the generator's output voltage is not yet established. Which
means an initial excitation is carried out. The voltage supplied from the separate excitation unit (14) is at almost the
same level as that of the battery voltage (because of an internal diode, the unit's forward voltage is about 0.5 V lower
than the battery voltage). When the generator's exciter voltage has risen and the output voltage of the rectifier (2) has
exceeded the voltage from the separate excitation unit (14), therefore, the voltage being fed to the rotor becomes zero.
As discussed in "Drive circuit (5)", however, the voltage being fed to the generator does not drop to zero because of
the drive circuit (5) connected. Also the separate excitation unit (14) has a built-in relay, the current of which keeps
flowing. In concrete, the following current is available.
*With generator's output voltage established:
About 10 mA at drive circuit + Relay working current about 25 mA.
*With key switch on:
About 10mA at drive circuit + Relay working current about 25 mA + (Battery voltage/rotor resistance) A
When the key switch (15) is turned on, a small current below the decimal that is inversely proportional to the rotor
resistance starts flowing continuously. (When the rotor voltage and rotor resistance are 12 V and 30 respectively,
for example, we have 12/30=0.4 A.) There will be no problem when the engine gets started soon enough. But if the
key switch (15) is at the ON position for too long a time, the battery (16) will be dead. Keep such possible trouble in
mind.
(7) Rectifier
As discussed in "Separate excitation unit"(14), the rectifier (2) is intended to rectify the exciter output voltage and
to feed power to the rotor. This component consists of diode stack and electrolyte capacitor.
(8) Key switch
Also as explained in "Separate excitation unit (14)", the key switch (15) is used to turn on the separate excitation
unit (14) and to feed power to the rotor and circuit (5).
(9) Battery
Referring back to "Drive circuit (5)", the generator is interrupted without the battery voltage being applied. It also
shuts down if the battery (16) is disconnected during operation.

[3] EMERGENCY RELAY CIRCUIT

(1) General

This is an automatic engine stopping device. This
device senses any abnormal situation on engine and
related parts, such as oil pressure, water temperature, or
fan belt broken (D1005 and V1305 only), occurring
during engine operation, and activates the stop solenoid
to cut off fuel to the fuel injection pump and stop the
engine.This relay has two independent timer functions, a
start relay and a stop relay.
The start relay does not activate this relay for a
specified time period after the engine has started.
IMPORTANT

• When this device stops the engine, it may be that
some minor damages to the engine has occurred.
To limit engine damage as mush as possible,
please do not make the faulty assumption that it
is a perfectly safety device.
(1) Emergency Relay
M-4
GENERATOR
W10130620
KiSC issued 10, 2016 A