Discharge Unit SSR

The IRS Discharge Unit SSR is a wear-free alternative to conventional discharge relays. It was designed for discharging capacitive DC links up to 1500 V DC. Thanks to solid-state relays, there is no contact wear even with short current peaks.

Technical description

To discharge a capacitive DC link, the IRS Discharge Unit SSR switches a connected discharge resistor onto the DC load.

The control input is active low. If a line breaks or the control signal or the supply voltage fails, the unit therefore discharges automatically.

The potential-free interlock contacts can be wired into a safety controller, for example to switch off the power supply automatically while a discharge is active. The status feedback shows that discharge current is actually flowing – and thus that the discharge resistor is intact. It is designed for a 100 Ω resistor, so that the status signal responds from a voltage of 60 V.

The two channels are galvanically isolated from each other and from the 24 V control side. They can discharge either two separate DC links or one DC link redundantly together.

The basic function needs only the 24 V supply and the control signal. Status signal and interlock contacts are optional and can be used depending on the application.

Applications

Test benches and test systems: Safe discharge of DC links in high-voltage test benches, for example for inverters and power electronics.

Redundant discharge: Both channels on one DC link, each with its own discharge resistor.

Two DC links: Each channel discharges its own DC link.

The IRS Discharge Unit SSR is available on its own or as a set with matching discharge resistors and the IRS Vol-Tran residual voltage monitor.