Soft Start

To limit inrush current.

Soft start is used extensively in industry.

I have found very little exact information.

Most are three phase black box units.

Unrepairable, must be returned for repair.

They probably use pulse width modulation.

Pulse density

Apply full power for one cycle,

no power for (xx) cycles. <ref>

Then full power for two cycles, etc.

How much power is needed to start a motor moving? <ref>

Depends on motor.

Need more info.

Model 1

• NTC resistor (low power)

Model 2

• Power Resistor in series
• Relay jumps resistor after timer

Model 3

• Power diode in series
• SCR PWM

Model 4

• CPU control
• Triac

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