At a Glance. Specifying a DIN-rail power supply looks like a simple capacity calculation, and it usually goes wrong in one of two ways: the output voltage class is chosen from habit rather than from the load, or the current is read from the nameplate without regard to derating. The PULS range we stock covers the four voltage classes that appear in control cabinets, from a 5 V / 15 W unit up to a 48 V / 50 W model, all within AC/DC power supplies.
1. The four output classes at a glance
| Model | DC output | Rated power | Input | Typical use |
|---|---|---|---|---|
| ML15.051 | 5 – 5.5 Vdc / 3 – 2.7 A | 15 W | 100–240 Vac wide range | Electronics, sensors, signalling |
| PIM60.121 | 12 – 15 Vdc / 5 – 4 A | 60 W | 100–240 Vac | Low-voltage actuators, displays, relays |
| PIC120.241D | 24 – 28 Vdc / 5 – 4.3 A | 120 W | 100–120 / 200–240 Vac | Standard 24 V control supply |
| ML50.105 | 48 – 56 Vdc / 1.1 A | 50 W | 100–240 Vac | 48 V loads, telecom and PoE-adjacent equipment |
Note the output ranges: these units are adjustable within the band shown, which is how the exact voltage at the load is trimmed to compensate for cable drop. The 24 V class is the default in European machine building, and the PIC120.241D is representative of that duty with a 24–28 Vdc adjustable output.
2. Sizing: current, not watts alone
- Sum the load currents from the device datasheets rather than the fuse ratings.
- Add inrush and start-up current. Capacitive loads, DC motors and some sensors draw several times their steady current at switch-on. A supply sized exactly to the steady load will trip or drop out.
- Apply derating for the cabinet. Output capability falls as ambient temperature rises, and side-by-side mounting reduces it further. Read the derating curve for the specific model and mounting orientation.
- Leave 20–30 percent headroom for future additions. Cabinet spare capacity is nearly always used.
- Check the input range. All four units accept a wide AC input, but confirm the behaviour on a DC input if the cabinet is fed from a battery system.
3. Features worth checking before you order
- NEC Class 2 compliance. The PIM60.121 is NEC Class 2 compliant, which matters where the supply feeds field wiring in North American installations and the wiring class affects the installation rules.
- Parallel and redundancy capability. Not every supply can be paralleled for redundancy or for higher output current without external decoupling.
- Overload behaviour. Continuous current and hiccup-mode characteristic differ between families and decide how the load behaves during a fault.
- DC-OK signalling and remote shutdown. Contacts and control inputs are often needed to sequence the machine safely.
- Width per rail. In dense cabinets the DIN-rail width is a design constraint, not a detail.
4. Replacing a failed supply
Power supplies are the most frequently replaced component in a control cabinet, and a like-for-like substitution is usually the right answer. Send the failed unit's model and full order code, the cabinet ambient temperature, and the measured load current. Where a family has been discontinued we will cross-reference to a current model with the same voltage class and equal or better current capability, and flag any change in terminal layout or width that affects the retrofit. Browse our PULS stock for current availability and the full specification of each model.