SunSaver Gen3 Load Overcurrent Short Circuit Protection

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Load Overcurrent & Short Circuit Protection

in the SunSaver

™

Gen 3 Controller

ABSTRACT: The new Morningstar Generation 3 SunSaver Controller improves upon the previous Generation

2 model by introducing new operational features and circuit protections. The purpose this whitepaper is to

discuss the new SunSaver’s Load Overcurrent & Load Short Circuit Protections. (For a complete list of the

SunSaver’s new features & protections, please refer to the following document available on the Morningstar

Technical Support Website:

www.morningstarcorp.com/en/support > “SunSaver Gen 3 Overview 8.12.pdf”)

The SunSaver Gen 3 (referred to as ‘Gen 3’) includes new Load Overcurrent and Load Short Circuit

Protections, previously not available in the SunSaver Gen 2 Controller (referred to as ‘Gen 2’). These

protections have proven to increase the reliability and robustness of the SunSaver load circuitry, particularly

when the controller is used with large or highly capacitive loads. Customers may find that some loads, which

previously ran on the Gen 2 controllers, are not suitable for use with the Gen 3 controllers. It is important to

understand the purpose and characteristics of the Gen 3 Load circuit protections so that load compatibility

issues can be minimized.

Summary of content (8 pages)

PAGE 1
Load Overcurrent & Short Circuit Protection in the SunSaver™ Gen 3 Controller ABSTRACT: The new Morningstar Generation 3 SunSaver Controller improves upon the previous Generation 2 model by introducing new operational features and circuit protections. The purpose this whitepaper is to discuss the new SunSaver’s Load Overcurrent & Load Short Circuit Protections.
PAGE 2
Load Overcurrent & Short Circuit Protection in the SunSaver Gen 3 Controller Background Both the Gen 2 and Gen 3 SunSaver controllers rely on power MOSFETs (transistors) to deliver current from the battery to the load terminals. Power MOSFET devices are very reliable so long as they are operated within their specified limits. Two important MOSFET characteristics for this discussion are current rating and maximum junction temperature (which are directly related).
PAGE 3
Load Overcurrent & Short Circuit Protection in the SunSaver Gen 3 Controller SunSaver Gen 3 Load Circuit The Gen 3 circuit improves upon the Gen 2 circuit with the addition of Overcurrent and Short Circuit Protection. Each is implemented using a different method. Overcurrent Protection is implemented in software and is intended to protect against slow increases in load current.
PAGE 4
Load Overcurrent & Short Circuit Protection in the SunSaver Gen 3 Controller Figure 2 shows the same SS-10L-12V controller as in Figure 1. This time, a greater number of cold incandescent lights are used than in our Figure 1 test. The startup current surge of this larger bank approaches 68A. This amount of current is too much for the controller’s transistors to safely handle and the hardware Short Circuit Protection has activated.
PAGE 5
Load Overcurrent & Short Circuit Protection in the SunSaver Gen 3 Controller Figure 4. A magnified look at what is happening in Figure 3 when the load turns on (when the yellow goes low-to-high). Figure 5 shows what happens if the same SS-20L-12V controller from Figures 3/4 tries to energize a 10,000uF capacitor load (uncharged). The load current (blue) approaches 185A before the controller’s Short Circuit Protection turns off power to the load terminals. This protects the power transistors from damage.
PAGE 6
Load Overcurrent & Short Circuit Protection in the SunSaver Gen 3 Controller ‘Non-L’ Gen 3 Considerations ‘Non-L’ Gen 3 SunSaver versions are differentiated from the ‘L’ versions by having no load overcurrent or short circuit protections [nor do they have a Low Voltage Disconnect (LVD) feature]. • ‘Non-L’ versions are those with no ‘L’ in the model name (e.g. SS-10-12V). • ‘L’ versions are those with an ‘L’ in the model name (e.g. SS-10L-12V).
PAGE 7
Load Overcurrent & Short Circuit Protection in the SunSaver Gen 3 Controller To reduce startup surge from high capacitance loads, a resistor may be placed in series with the load. The resistor forms an R-C circuit with the load capacitance and serves to limit the magnitude and rise-time of the startup current. The resistor value(s) appropriate for a particular load depends upon the load input capacitance and the wire gauge / length being used to connect the load to the Load terminals.
PAGE 8
Load Overcurrent & Short Circuit Protection in the SunSaver Gen 3 Controller Summary The Generation 3 SunSaver ‘L’ Controllers employ both software-controlled steady-state overcurrent protection and hardware-controlled short circuit protection (for high current surges). These protections are two of many new features introduced in the Gen 3 SunSaver models. They have proven to increase the reliability and robustness of the SunSaver load circuitry over the long-term.