Three Methods for Reducing Nominal Operating Power in Relays
Every day energy is being wasted through inefficient technologies – ultimately costing people money. To help alleviate this issue, new features are being added to the components designed into various devices. Relays, for examples, can have huge energy saving benefits when designed into applications like Photovoltaic (PV) Systems.
The nominal coil holding voltage of a Relay can be reduced 100 milliseconds after the contacts have closed. Relays can minimize the impact of the entire systems power consumption by taking advantage of reduced coil holding voltage techniques. Here are the three most common methods to reduce coil holding voltages.
CR CIRCUIT METHOD
Apply a voltage over nominal coil voltage (around 130%V). After the Relay is ON, the power consumption is controlled using the values of the Relay coil resistance, Capacitor and Resister (R).
Operate by turning on SW1 at the nominal voltage. After the Relay is closed, turn SW2 on and release SW1. Set the coil holding voltage using resistance (R), and the Relay coil resistance to reach the voltage you are aiming for (around 50%V).
PULSE WIDTH MODULATION METHOD
Turn the MOSFET on to supply voltage to the Relay coil and make sure the duty ratio is at 100%. After the contacts are closed, start PWM control with MOSFET duty ratio at 50% and control the power consumption. A recommended PWM control frequency is 20kHz to 100kHz.
To achieve the lowest coil holding voltage using the above methods, it is important to design in the appropriate Relay. Below is a list of recommended Relays, manufactured by Panasonic, and their specifications. These Relays are some of the best in the industry and can achieve the lowest operating coil holding voltage.
|Product||Contact Arrangement||Current Capacity||Coil Holding Voltage||Nominal Operating Power||Coil Holding Power Consumption|
|LF-G||1FormA||22A, 31A||35%V of nominal coil voltage||1,400mW||170mW|
|HE-S||2FormA, 2FormA + 1B||35A||30%V of nominal coil voltage||1,880mW||310mW|
|HE-PV||1FormA||35A, 48A, 90A||40%V of nominal coil voltage||1,920mW||170mW|