DS3800HDPA | GE Mark V DC Output Module

Description

Product Introduction

The DS3800HDPA is the DC sibling to the HDDB—designed for 125V DC loads commonly found in turbine control systems, such as DC solenoids, emergency trip valves, and status relays. While most modern plants use 24V DC, many legacy systems and certain safety-critical applications still use 125V DC, which is a standard voltage in power plants (derived from station batteries). This board uses MOSFET outputs instead of triacs, providing faster switching and lower on-state resistance than AC output boards. If your plant runs 125V DC field devices, the HDPA is your workhorse.

We’ve measured the HDPA’s response time at about 1ms from the controller command to output switching—much faster than the AC boards’ zero-crossing delay. The MOSFETs have a low on-resistance (about 0.1Ω), so they dissipate minimal heat even at 1.0A. The board also includes flyback diodes across each output to protect the MOSFETs from inductive kickback when driving solenoids. The status LEDs show the output state, but they’re powered from the 5V logic rail, not the field voltage—this means they work even when the field supply is off, which can be confusing during troubleshooting.

Key Technical Specifications

Compatible Replacement Models

Frequently Asked Questions (FAQ)

Q: Can the HDPA drive a 24V DC load?
A: No. The HDPA is designed for 100-150V DC. Driving a 24V load will result in either the output not switching off (if the load current is too low for the MOSFET) or the load receiving 125V and being damaged. If you have 24V DC loads, use the HCIC or other 24V DC output boards. The HDPA is specifically for high-voltage DC applications.

Q: How does the flyback diode protect the output when driving a solenoid?
A: When a solenoid is turned off, the collapsing magnetic field generates a high voltage spike (inductive kickback) that can damage the MOSFET. The HDPA includes a flyback diode across each output that clamps this voltage to a safe level, protecting the output stage. The diode is internal, so you don’t need to add external diodes for standard inductive loads. However, if you’re driving a very large solenoid (over 0.5A inductive), you may need an external freewheeling diode.

Q: The HDPA’s status LEDs are powered from the 5V logic rail. What happens if the field supply is off?
A: The LEDs will still indicate the output state as commanded by the controller, even if the field supply is off. This can be misleading—you may see the LED on but the load won’t be energized because there’s no field voltage. When troubleshooting, always verify the field supply voltage at the load terminals. The LED indicates the logic state, not the actual presence of field power.

Q: Can I use the HDPA with a 125V DC power supply derived from station batteries?
A: Yes, that’s the intended application. The HDPA accepts 100-150V DC, which covers the typical station battery voltage range (110-125V). The board includes input filtering and transient suppression to handle the noisy DC supply typical in power plant battery systems. However, if your battery voltage tends to exceed 150V during charging, you’ll need an external voltage regulator to protect the board.

Q: What’s the switching time of the HDPA compared to AC output boards?
A: The HDPA switches in about 1ms, which is much faster than the AC output boards (which have zero-crossing delays of up to 8ms). This makes the HDPA suitable for fast-acting control applications where response time matters. However, the board’s 16-channel capacity is the same as the AC boards, so you don’t sacrifice channel count for speed.

Q: How do I connect a DC solenoid to the HDPA?
A: Connect the solenoid’s positive terminal to the HDPA’s output channel (switched side) and the negative terminal to the field supply common. The board’s flyback diode is wired internally, so you don’t need an external one. Ensure the solenoid’s current rating is under 1.0A (resistive) or 0.5A (inductive). If your solenoid draws more than 0.5A inductive, consider using an external contactor or a higher-rated board like the HDPB.

Q: Can I drive a 125V DC motor with the HDPA?
A: Not directly. The HDPA is rated for 1.0A continuous, which is insufficient for most motors. You could use the HDPA to drive a contactor or relay that controls the motor, but not the motor itself. If you need to drive a DC motor, you’ll need a separate motor drive or a contactor board. The HDPA’s MOSFETs are not designed for high inrush currents associated with motor starting.

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