KiwiAC driving Switch EV Induction motor

We have recently been helping to commission a new induction motor made be Switch EV (a NZ manufacturer).  We are pretty happy with the results so far and hope to be showing vehicle based dyno (dynamometer) results in the near future. For now though, here are some videos and images to whet your appetite.

The motor shown is being driven via a Gen 1 SKAI with a Greenstage KiwiAC control board and a 330V Lithium Iron Phosphate battery pack providing the energy.

As you can see the brake rotor on the dyno gets quite hot (hence the smoke!), it is absorbing the energy from the motor when we load it up to measure the torque.

Zero RPM torque tests showed we were achieving in excess of 600 Nm, which is "heaps" of torque and matching nicely with design goals.  Unfortunately the dyno didn't quite measure up and soon after we snapped the shear pin on the shaft.

Never mind, the dyno did its job and the Switch EV motor is ready for the next stage!  Stay tuned for more information...

Dyno Progress

For a while now we had the plan to build a dynamometer out of two Siemens made Ford Ranger AC motors. While no calibrated results could be made (through measuring the torque directly) the contraption would be very useful for comparative analysis of motor control regimes and settings.

The first steps (October last year) involved working out how to couple the two together. The motor shaft is hollow to allow a further shaft to run directly through the motor. The output end of the shaft has a helical gear directly machined into it, for a now unavailable planetary gear set. Others have suggested directly welding to the shaft, some have success using taper-lock devices directly on the gear.

In our situation, because of its non-critical nature (a failure is not likely to put anyone in a compromised situation), we decided to go with another untested route – developing a bush that works somewhat like an inside out double ended collet holder. Made of brass it may not be as strong as the rest of the equipment, but simple to make on the lathe, and not likely to damage the motors for future applications.

As previously mentioned Stephen designed and organised an adaptor plate for bolting the motors together. The motors are now coupled, and spinning just about as freely as individually so must be fairly close to aligned.

Due to the weight of the combined motors (over 130kg) we wanted to be able to wheel them around. We started to think about building a trolley but instead opted for far cheaper and easier option - a 200kg rated handcart.
Next came the job of hooking up the motor encoder and temperature sensors. Reportedly there isn't a plug available for the encoder connector on the motor, so a new arrangement is required. 

We made a stainless piece that reduces the hole to suit the M23 servo-motor style encoder connector used on standard Siemens motors.

 I don't think that the plastic connectors that the motors are delivered with were originally part of the plan. The tapped hole for the closest cover bolt breaks through into the hole for the connector. Worse still, an o-ring seal sits beyond where the bolt hole breaks through, which means the o-ring is damaged every time the fitting is removed or put back in. Not a clever design, but we will run with it for the mean time.

A little bit of fabrication

Over the last couple of months there have been a few changes to accommodate the new race battery pack in the GS750V and to brace the motor appropriately as we head towards full torque output.  Below you can see the new brackets that prevent the motor's aluminium body from carrying all the torque and they also provide a new mounting point for the the inverter just above the motor.

Multi purpose bracing brackets

In addition to that, we have put together our dual motor dyno ready for fine tuning of the motor control algorithms under development in the Tumanako project.

Dyno for motor tuning

Big thanks to Stephen for driving the details and making this happen and also to the Spaceships crew and PureAdvantage for the support along the way.  Thanks also to the fine Engineering work and support provided by Abel Metal Products, Primero Profiles, Tordeich Engineering and Ladarac.

We are now ready for the batteries!

Saker GS750V Dyno run

Thursday evening we commissioned the Tumanako control board for the first time on the test bench motor (check it out here). This gave us confidence to install and use it in the GS750V for the dyno run the next day...



This optimism proved to be slightly misplaced as we uncovered a couple of unexpected digital IO issues and a motor configuration and/or DC supply not up to establishing a baseline set of figures from the dyno. So not 100% happy, but given that our goals for the day included equipment familiarisation and commissioning the rectified DC supply, it was still a valuable exercise.

Big thanks to Ed, Mark, John and the Wintec team for making the day possible.

Next up, a test rig for the GS750V's WS28 Motor (1.1kW test rigs only go so far), a bikini pack (2 minute hill climbs) and more Open Source inverter progress (bring on the KiwiAC!).