Lincoln Electric V155-S Pulse Width Modulation, Minimum Output, Sec 31 m/sec 33 m/sec

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E-7	THEORY OF OPERATION	E-7
	Figure E-7

MINIMUM OUTPUT

2 sec 31 m/sec

33m/sec

MAXIMUM OUTPUT

	31 m/sec
	33 m/sec
PULSE WIDTH MODULATION	MAXIMUM OUTPUT

The term PULSE WIDTH MODULATION is used to	By holding the gate signals on for 31 microseconds
describe how much time is devoted to conduction in	and allowing only 2 microseconds of off time during
the cycle. Changing the pulse width is known as	the 33 microsecond cycle, the output is maximized.
MODULATION. Pulse Width Modulation (PWM) is the	The darkened area under the min. curve can be com-
varying of the pulse width over the allowed range of a	pared to the darkened area under the max. curve. The
cycle to affect the output of the machine.	more darkened area, the more power is present.

MINIMUM OUTPUT

By controlling the duration of the gate signal, the IGBT is turned on and off for different durations during a cycle. The top drawing shows the minimum output signal possible over a 33-microsecond time period.

The shaded portion of the signal represents the IGBT, conducting for 2 microseconds. Since only 2 microseconds of the 33-microsecond time period is devoted to conducting, the output power is minimized.

INVERTEC® V155-S