Black & Decker VEC054D instruction manual Principle of Operation, Power Inverter Output Waveform

•Overload and over-temperature shutdown activated if AC output exceeds rated watts

•AC short-circuit shutdown

•Low voltage audible alarm (sounds at 10.5 volts input)

•Low-voltage shutdown (activates at 10.0 volts DC)

•High-input voltage shutdown (activates at above 15.5 volts DC)

MAXX SST™ uses a 12 volt DC power source like those found in motor vehicles, or it can be operated using multiple battery configurations with commercial battery chargers or solar battery chargers. For most heavy-duty applications, a multiple battery configuration and the use of deep-cycle batteries is required.

When using multiple batteries, inverters can be operated from one of the vehicle 12 volt batteries, so there’s always one battery with adequate charge to start an engine.

MAXX SST™ includes a high-surge capability. This is required to start heavy loads, such as motors and other inductive devices.

PRINCIPLE OF OPERATION

The MAXX SST™ inverter converts 12 volt DC (direct current) from a vehicle battery or other 12 volt DC power source to standard 120 volt AC (alternating current) household power.

It converts power in two stages (see the diagram below). In the first stage, the inverter raises the 12 volt DC input to 145 volts DC. This MAXX SST™ inverter uses high-frequency conversion techniques that replace bulky and heavy transformers found in older inverters. In the second (output) stage, the inverter converts the 145 volt DC to 110/120 volt AC using multiple banks of metal-oxide semiconductor field-effect transistors (MOSFETs). The unit’s solid-state circuitry ensures excellent overload protection and the ability to operate reactive loads such as those found in inductive motors. In this stage, the inverter functions as a high-power bipolar switch, alternately applying opposite polarity to the AC outlet HOT and NEUTRAL terminals.

See the “Specifications” section for wire gauges and fuse amperages.

TERMINAL	DC TO DC
BLOCK	CONVERTER

AWG

WIREINTERNAL WARNINGS & PROTECTION CIRCUITS

ANL

FUSEVOLT, AMP METERS* (external)

OVER TEMP &

VOLT INDICATORS

+

–

145 VDC

MOSFET

BIPOLAR SWITCH BANKS

NEUTRAL HOT

AWG AWG

WIRE + – WIRE

12 VOLT DC INPUT FROM BATTERY

Notes: Simplified diagram.

Cables, fuse and battery are not included and

ON/OFF

SWITCH

(2, 3 OR 4)

OUTLETS

GROUND FAULT

SENSE

must be supplied by user.

The Power Inverter Output Waveform

The AC output waveform of the Power Inverter is known as “modified sine wave.” It is a waveform that has characteristics similar to the sine wave shape of utility power. This type of waveform is suitable for most AC loads, including linear and switching power supplies used in electronic equipment, transformers, and motors.

The modified sine wave produced by the Power Inverter has an RMS (root mean square) voltage of 115 volts, which is the same as standard household power. Most AC voltmeters (both digital and analog) are sensitive to the average value of the waveform rather than the RMS value. They are calibrated for RMS voltage under the assumption that the waveform measured will be a pure sine wave. These meters will not read the RMS voltage of a modified sine wave correctly. They will read about 20 to 30 volts low when measuring the output of the inverter. For accurate measurement of the output voltage of this unit, use a true RMS reading voltmeter such as a Fluke 179, Fluke 79 III series, Beckman 4410 or Triplett 4200.

Modified Sine Wave and Sine Wave Comparison

4