Guardian Technologies 4456 Automatic Operating Parameters, Automatic Operating Sequences, Section

GENERAL INFORMATION

PART 1

SECTION 1.7

AUTOMATIC OPERATING PARAMETERS

INTRODUCTION

When the prepackaged generator is installed in conjunction with a prepackaged transfer switch, either manual or automatic operation is possible. Manual transfer and engine startup, as well as manual shutdown and retransfer are covered in Section 1.6. Selection of fully automatic operation is also discussed in that section. This section will provide a step-by-step description of the sequence of events that will occur during automatic operation of the system.

AUTOMATIC OPERATING SEQUENCES

PHASE 1 - UTILITY VOLTAGE AVAILABLE:

With utility source voltage available to the transfer switch, that source voltage is sensed by a circuit board in the generator panel and the circuit board takes no action.

Electrical loads are powered by the utility source and the AUTO-OFF-MANUALswitch is set to AUTO.

PHASE 2- UTILITY VOLTAGE DROPOUT:

If a dropout in utility source voltage should occur below about 60 percent of the nominal utility source voltage, a 15 second timer on the circuit board will start timing. This timer is required to prevent false generator starts that might be caused by transient utility voltage dips.

PHASE 3- ENGINE CRANKING:

When the circuit board’s 15 second timer has finished timing and if utility source voltage is still below 60 percent of the nominal source voltage, circuit board action will energize a crank relay and a run relay. Both of these relays are mounted on the circuit board.

If the engine starts, cranking will terminate when generator AC output frequency reaches approximately 30 Hz.

PHASE 4-ENGINE STARTUP AND RUNNING:

The circuit board senses that the engine is running by receiving a voltage/frequency signal from the engine run windings.

When generator AC frequency reaches approximately 30 Hz, an engine warm-up timer on the circuit board turns on. That timer will run for about ten (10) seconds.

The engine warm-up timer lets the engine warm-up and stabilize before transfer to the "Standby" source can occur.

NOTE: The engine can be shut down manually at any time, by setting the AUTO-OFF-MANUAL switch to

OFF.

PHASE 5- TRANSFER TO "STANDBY":

When the circuit board’s engine warm-up timer has timed out and AC voltage has reached 50 percent of the nominal rated voltage, circuit board action completes a transfer relay circuit to ground. The transfer relay is housed in the prepackaged transfer switch enclosure.

The transfer relay energizes and transfer of loads to the "Standby" power source occurs. Loads are now powered by standby generator AC output.

PHASE 6- "UTILITY" POWER RESTORED:

When utility source voltage is restored above about 80 percent of the nominal supply voltage, a 15 second timer on the circuit board starts timing. If utility voltage remains sufficiently high at the end of 15 seconds, retransfer can occur.

PHASE 7- RETRANSFER BACK TO "UTILITY":

At the end of the 15 second delay, circuit board action will open a circuit to a transfer relay (housed in the transfer switch). The transfer relay will then de- energize and retransfer back to the utility source will occur. Loads are now powered by utility source power. On retransfer, an engine cool-down timer starts timing and will run for about one (1) minute.

PHASE 8- GENERATOR SHUTDOWN:

When the engine cool-down timer has finished timing, and if the minimum run timer has timed out, engine shutdown will occur.

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