The Motor

The motor I’m using is a Kostov 11″ HV. I picked it up “gently” used on eBay for $1,000. A motor of this size is more often used in a truck or van. This gave me the ability to both forgo the use of a transmission and maintain strong performance. No shifting is ever necessary.

K11HV
Rated Volts185v/240v
Rated Amps250a/210a
Rated Power45kW
RPM5300/5500
Weight180lbs
DatasheetK11 Datasheet
PerformanceK11 Motor Graph

This thing is pretty huge, so I enlisted the help of a local fabrication shop, Wagner Fabrication, to make the front mounting plate. The adapter is 3/8″ steel with ears welded onto it. The second mount was made by Glaser Steel. I went there for supplies and they said they could roll and weld the ring for me. It cost hardly anything, so I happily had them do it while I was getting the rest of my steel for the mounts. The motor had to be raised about 4″, so I used some square stock under the mounts to locate everything. I painted it all with some gloss black Rustoleum and mounted it with some 5/8″, grade 8 bolts.

The motor is rated for 45kW, which is pretty significant. I’m overloading it to 200Kw for short bursts, which is equivalent to 269hp. In a 1700lb car, that’s fast! It will light up the tires without too much effort from a standstill.

This motor has an odd feature where it can be wired either in parallel or in series. In parallel, the field coils are wired in parallel, and then in series with the armature. In series, the field coils and armature are all wired in series. The ratings change depending on how you wire it up, as a result. This was beneficial to achieve a higher RPM at a lower voltage for my build. These additional wiring options are why you will noticed six terminals on the motor, rather than the standard four. Two of them go to the armature, and then each field coil has two more.

In addition, the motor comes equipped with interpoles. These additional coils help to stabilize the magnetic field within the motor at higher RPM, which allows you to keep the brushes neutrally timed. Without interpoles, the brushes must be advanced to prevent excessive arcing and burning the commutator at high RPM. This comes at the cost of an armature with a smaller diameter, however. The armature in this motor is similar to one in a 10″ motor, despite the 11″ case.

The motor has a cooling fan mounted internally on the shaft, and an electric fan mounted on the back of the case. I have the electric fan connected to a temperature sensor to turn it on when the motor heats up. The thermistor is bolted to a brush holder to get as accurate a reading as possible. I used some muffler repair paste to glue the thermistor into a ring terminal, and I just ran one of the brush bolts through it.

There was a lot of shipping damage that I had to take care of when I got the motor, as you’ll notice in the photos.

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