Sevcon Gen4 + Heinzmann PMS120W: Encoder Compatibility and Full Configuration Guide

ByPriya Nair

Start with the encoder — everything else depends on it

Before opening DVT or connecting a single wire on a Sevcon Gen4, you need to know which encoder is inside your PMS120W. The Heinzmann PMS120 series has shipped with at least two distinct encoder types across its production run: a sin/cos encoder and an SSI (Synchronous Serial Interface) encoder. These are not interchangeable from the controller’s point of view, and assuming the wrong one wastes a lot of time.

The standard PMS120W at 96 VDC is generally listed with a sin/cos encoder — often the RLS RMB29A01. Some PMS120 units, particularly those pulled from specific OEM applications like the Brammo Enertia motorcycle, carry an SSI encoder instead. SSI is a purely digital serial protocol. The Sevcon Gen4 does not support it. If that’s what you have, the Gen4 simply will not run this motor without replacing the encoder or switching to a different controller.

Check your motor’s documentation or the encoder housing itself before going any further. Heinzmann’s official downloads page for the PMS120 is the first place to look. If no datasheet turns up, contact Heinzmann directly — they can confirm exactly what’s fitted to your specific unit.

Sin/cos encoder: Gen4 compatibility and the hardware check you can’t skip

If your PMS120W has the sin/cos encoder, the Gen4 is designed to work with it. There’s one hardware caveat first.

Check the controller’s hardware revision

Not all Gen4 units have the analog front-end modification required for sin/cos inputs. Open DVT and check the hardware version of your specific controller before assuming it’s capable. If yours lacks that modification, the options are sourcing a compatible Gen4 variant or swapping in a digital incremental encoder — neither is quick.

DVT software and the IXXAT dongle

Configuration requires BorgWarner’s DVT (Device Verification Tool) and an IXXAT USB-to-CAN V2 adapter. DVT will not communicate with the Gen4 through any other CAN interface — the IXXAT dongle is a hard requirement. License activation after submission typically takes a day or two, so don’t leave this until you’re sitting next to the vehicle ready to start.

Setting the encoder type in DVT

In DVT, set object 0x4630, sub 3 to 5 to select sin/cos as the encoder type. Phasing is critical: cos must lead sin by 90 degrees in the forward direction. If the motor runs backwards or throws encoder faults on startup, swapping the sin and cos channel wires is the first thing to try.

Signal scaling matters too. Sin/cos encoders generate a signal of a few volts peak-to-peak, and DVT lets you adjust the input scaling to match your specific encoder’s output. Get this wrong and position measurement drifts under load, which shows up as unstable torque or poor low-speed control.

Measuring the encoder offset angle

The Gen4 needs the rotor’s electrical angle relative to the encoder’s reference position. DVT includes a PMAC Encoder utility accessible from the main DVT Helper page that calculates this automatically. The process: spin the motor shaft externally with a cordless drill while DVT captures a trace of the Ud and Uq values. The utility reads the offset angle directly from that trace.

A few practical points. Keep the motor disconnected from the main high-voltage bus while spinning it. Aim for a consistent, moderate speed — erratic spinning produces noisy trace data. Run the measurement two or three times and confirm the offset value is repeatable before writing it to the controller.

If the encoder is SSI

SSI encoders on the PMS120 are the harder path. The Gen4, most Curtis controllers, and the majority of DIY-friendly PMAC controllers don’t have SSI decoder hardware. Three routes people have taken:

  • Replace the encoder with a sin/cos or incremental quadrature type that fits the motor housing. This is the cleanest fix if the mechanical interface works out.
  • Use a Sigmadrive controller, which natively supports SSI. These are less common outside Europe and harder to source in many regions.
  • Add an SSI-to-quadrature converter board between the encoder and controller. Industrial adapters for this exist, but you’re adding latency and another potential point of failure.

Before ordering anything for an encoder swap, confirm the pole-pair count on your motor — the replacement encoder’s configuration needs to match.

Contacting Heinzmann and BorgWarner

Both manufacturers are worth reaching early in the process. Heinzmann can confirm the exact encoder fitted and may provide motor constants — pole pairs, Ke, winding inductance — that save significant auto-tuning time in DVT. BorgWarner (which acquired Sevcon) maintains a customer portal for the latest DVT software and handles configuration support tickets. Outside a commercial relationship turnaround is slower, but they do respond.

Also worth downloading separately: the Sevcon PMAC application note (the PDF sometimes labelled AN-EK016 or simply the PMAC app note). It covers encoder wiring diagrams, input scaling procedures, and fault code explanations that don’t appear in the main Gen4 reference manual.

Sources


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