3 Important Considerations Before Selecting a MAXQ™ High Current DC SSR (Advanced Model)

by Peter Zhang August 13, 2018

The end result of choosing MAXQ™ high current solid state relays over electromechanical relays is a switch that is noise-free, arc-free, capable of operating 100x faster, and last 100-1000x longer. However there are 3 important factors to consider if your application is suitable for solid state switching:

1. Availability of a 12VDC or 12-24VDC, 50mA Power Supply

For the advanced models, a 12VDC or 12-24VDC power supply is needed to power the relay's supervisory circuit. You may obtain this power by using any stand-alone power supply.

2. Cooling Requirements

Due to conduction losses, solid state relays at high currents will generate significant heat that must be dissipated. You must take into account of the each relay's thermal footprint as indicated on the last page of the data sheet. Consider using MAXQ™ relays with FET output whenever suitable as their ON resistance can be as low as 0.4mΩ; you may use multiple FET output relays in parallel only, to further reduce conduction loss.

3. Current and Voltage Rating

Selecting the correct ratings is a crucial aspect in determining a solid state relay's reliability. SSR’s current rating corresponds to the maximum current that should pass through the relay before possible damages occur to SSR’s internal components. Most common SSR failures are the result of insufficient margins against inrush current, transient overvoltage and back EMF spikes.

For selecting the current rating:

Ensure rated current is at least 50% of the peak current value
At least 1.5x the operating current.

For selecting the voltage rating:

1.25x the peak voltage if voltages are clamped.
Consider 2x the operating voltage for unclamped resistive load, 5-10x for unclamped inductive loads.

For more information, please refer to each relay's data sheet or contact us directly at 1-844-741-2580 | info@nominalcontrols.com