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SCR vs. PWM - Benefits and Drawbacks

The LGC400-10 is a SCR-based DC motor control

1. SCR Benefit #1 - Cost

SCR controls cost less than their PWM counterparts. This intuitively makes sense since the power section of a SCR control is a simply a rectifier bridge, while the PWM control has a diode bridge that costs roughly the same, plus the additional PWM components like BUS capacitors and MOSFETs or IGBTs.

2. SCR Benefit #2 - Size

A SCR DC motor control will typically be smaller than a comparable PWM DC motor control. A PWM contains all of (or similar) components as the power section of a SCR, and then some. However, other features on the drive may make a difference in size. A SCR control with a field supply, tach feedback, and isolation will be larger in mounting area than a PWM without those features. However, SCR controls are smaller in height to same power capable PWM controls as the SCRs do not need the tall BUS capacitor.

3. SCR Benefit #3 - Heat Generation 

As with benefits #1 and #2, this too is related to the fact that PWMs contain all of the same power circuitry as SCRs. Therefore, the PWM