Choosing between an uninterruptible power supply and a control transformer isn't like comparing two versions of the same device. Both are Emerson products that belong in an industrial panel, but they solve different problems. The SDU500B keeps a load powered when the main feed drops. The SolaHD E150 changes a higher incoming line voltage to a lower control voltage. Pick the wrong one and your panel either loses uptime or never receives the voltage it needs.
Quick verdict
Choose the Emerson SDU500B when you need short-term ride-through power for existing AC equipment and want a space-saving unit. Choose the SolaHD E150 when your real task is voltage change: turning a higher plant voltage into control power without spending more than necessary.
Comparison
| | Emerson SDU500B | SolaHD E150 |
| Price | $225.00 | $79.95 |
| Type | Uninterruptible Power Supply (UPS) | Industrial Control Transformer |
| Mounting | DIN Rail Mount | Epoxy encapsulated; mounting hardware included |
| Condition | New - Open box | New - Open box |
| What it does | Supplies backup power to a 120V AC load | Steps down higher plant voltage to 120V control power |
Where each product wins
The SDU500B wins when uptime matters. Its 300W output gives a small instrumentation or control load a cushion during a flicker or short outage, and its compact design keeps it panel-ready. The E150 wins when you're starting with a higher line voltage and need to create a control circuit. Its available primary and secondary tap options make it a straightforward fit for common single-phase, 50/60Hz installations.
Emerson SDU500B Uninterruptible Power Supply 120V AC DIN Rail
The SDU500B is the product to reach for when an outage can't be allowed to shut down your controls. Its 300W output is enough for small instrumentation and control loads, and the DIN Rail Mount style keeps it tidy in a crowded panel. At $225.00, it costs more than the SolaHD transformer, but it's doing a different job: it can keep your equipment running when the main feed drops. The trade-off is that it is not a voltage-changing device. It expects AC at its nominal input voltage, so if your panel is fed from a higher line voltage, you'll still need a transformer in front of it. For anyone with an existing AC control circuit, this UPS is the protective choice.
NEW Emerson SolaHD E150 Industrial Control Transformer 150VA 240x480V to 120V
The SolaHD E150 solves the voltage problem. It's a 150VA epoxy encapsulated control transformer with a primary rated for 240x480V AC and a secondary output of 120V AC, and it also supports alternate 230x460 and 220x440 primary connections with 115/110 secondary taps. That range makes it useful in single-phase, 50/60Hz control panels where incoming line voltage varies by site. The package includes mounting hardware, shorting clips, and a fusing instruction sheet, so installation can move quickly. The limitation is that it's a transformer, not a UPS: it won't keep power flowing during an outage. If you need both voltage change and backup, it has to be paired with a separate UPS. The 150VA rating also means it's best suited to small control loads rather than heavy machinery.
Final choice by use case
Choose the SDU500B when the load needs ride-through power. Choose the E150 when the panel needs a lower control voltage created from a higher line feed.
