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SPMD1404 vs SPMD1424: How to Source the Right Unidrive SPM Power Module
A practical comparison of SPMD1401, SPMD1404, SPMD1423 and SPMD1424—covering brake configuration, single-module ratings, parallel assemblies and the information needed for a precise spare-parts inquiry.
A request for “a 160 kW SPMD module” is not specific enough to identify the right replacement. The four order codes in this brief belong to the Control Techniques Unidrive SPM modular drive family, but their brake-transistor configuration and current-rating steps differ. The installed rectifier and drive arrangement matter as much as the inverter module label.
Why this matters now: Nidec lists Unidrive SP Modular among its superseded AC drives—products no longer in volume production. That is a reason to document installed systems and plan spares carefully, not evidence that one SPMD model automatically replaces another or that every spare is unavailable.
Read the complete SPMD order code
The manufacturer defines SPMD as a DC-input inverter power stage. In these four codes, 1 identifies the frame size, 4 the 380–480 V class, the next digit the internal brake-transistor configuration, and the final digit the current-rating step.
Therefore, SPMD1404 and SPMD1424 share a current-rating step but not a brake configuration. SPMD1423 and SPMD1424 share the no-brake configuration but not the current step. Exact-nameplate matching remains the starting point for a replacement.
Four models, three current steps
The figures below are from the manufacturer’s Unidrive SPM User Guide, Table 3-7. They describe one module in the stated 400 V motor-drive arrangement, not a universal rating for every assembled cabinet.
| Exact model | Brake transistor | Normal Duty continuous A / motor kW | Heavy Duty continuous A / motor kW | Main ordering distinction |
|---|---|---|---|---|
| SPMD1401 | Fitted | 205 A / 110 kW | 180 A / 90 kW | Lower current step; do not order by voltage class alone. |
| SPMD1404 | Fitted | 335 A / 185 kW docked; 350 A / 200 kW undocked | 290 A / 160 kW | Same rating step as 1424, different brake configuration. |
| SPMD1423 | Not fitted | 290 A / 160 kW | 246 A / 132 kW | No-brake configuration; lower current step than 1424. |
| SPMD1424 | Not fitted | 335 A / 185 kW docked; 350 A / 200 kW undocked | 290 A / 160 kW | Check the original brake circuit before considering 1404. |
Ratings shown at 400 V nominal motor power. “Docked” and “undocked” describe whether the rectifier is mounted directly above the inverter or independently. Ambient temperature, switching frequency, low-speed torque and overload requirements can change the permissible rating; confirm against the installed design.
SPMD1401 / smaller current step
Use the exact order code when maintaining an existing 1401 position. A higher-rated SPMD is not an automatic substitute: verify the associated rectifier, input reactor, control setup and cabinet arrangement first.
SPMD1404 / brake fitted
The “0” configuration includes the internal brake transistor. If the original drive uses a braking resistor, a no-brake module must not be assumed to preserve that function.
SPMD1423 / no brake, step 3
Its Heavy Duty continuous rating is 246 A / 132 kW in Table 3-7, rather than the 290 A / 160 kW shown for the step-4 models.
SPMD1424 / no brake, step 4
Its current step matches 1404, but the internal brake transistor is not fitted. Confirm the full module nameplate, installed brake arrangement and drive parameters before any proposed substitution.
Check the assembly—not just the inverter
In the guide, SPMC is a controlled rectifier and SPMU an uncontrolled rectifier. They are not names for the SPMD control module. The Table 3-7 single-module 400 V combinations shown here use SPMC1402; the input reactor is INL401 for the step-1 and step-3 units and INL402 for step 4.
Parallel example: Table 3-8 rates a two-module SPMD14X4 400 V arrangement at 636 A Normal Duty continuous output, with specified rectifier, input reactor and output-sharing choke components. This is not 350 A × 2; parallel-system derating is already included in the manufacturer’s table. Request the complete cabinet configuration before quoting a module for a parallel drive.
Choose the correct maintenance route
Restore the existing system
When the aim is to return an established machine to its documented configuration, start with the identical full SPMD order code. Verify the connected rectifier, braking circuit, module count, parameter backup and software version before installation.
Plan a system upgrade
If motor capacity, braking function, controls or cabinet architecture will change, treat it as an engineered retrofit. Nidec lists an upgrade path from Unidrive SP to the Unidrive M family, but that guidance does not establish a one-for-one, plug-in replacement for these SPMD modules.
What to send Moore for a useful quote
Moore’s catalog includes dedicated pages for SPMD1423 and SPMD1424. For all four models discussed here, provide enough information to distinguish an exact spare request from a system-change request:
- Clear photo of the complete SPMD nameplate
- Exact model and required quantity
- Single-module or parallel-module arrangement
- Installed SPMC/SPMU rectifier model
- Input reactor and output-sharing choke labels
- Brake-resistor connection and brake function
- Motor nameplate, duty and existing parameters
- Delivery destination and technical question
Recommended Unidrive SPMD models
Use the left and right arrows to compare exact-model product pages and Frida quotation routes. Final selection still depends on the complete installed drive assembly.
Need SPMD1401 or SPMD1404 instead? Send the complete label and installed-system details to Moore for an exact-model inquiry. Availability is confirmed during quotation.
Ask about an exact SPMD module
Send your nameplate photo, quantity and installed drive configuration to Frida at Moore Automation. Product condition, availability and shipment details are confirmed during the quotation process.
Quick answers
Can SPMD1424 replace SPMD1404?
Do not assume so. They share a current-rating step but differ in internal brake-transistor configuration. Check the original braking circuit and obtain an engineering assessment for any proposed change.
Can I multiply one module’s rating by the number of modules?
No. Use the applicable manufacturer parallel-assembly table. Table 3-8 includes the required derating and specifies associated rectifier, reactor and sharing-choke combinations.
Does “superseded” mean the installed SPM system must be replaced now?
No immediate replacement follows from that status alone. Compare maintenance needs, spare-part sourcing and the cost and scope of a planned retrofit for the actual machine.
Is SPMC1402 another SPMD power module?
No. The manufacturer describes SPMC as a controlled rectifier. SPMD is the DC-input inverter power stage; both can be part of the same configured drive assembly.
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