Kostov Motors

Kostov EV motors are designed with an ICE conversion/OEM use in mind.

  Some of their features are:
-optimized rpm so they are as close as possible to an internal combustion engine.
-larger and stronger commutators to minimize the possibility of lifting bars.
-class H insulation throughout the motors and heavy duty SKF bearings
-dual shaft, thermal cut off sensor and stainless springs as standard
-thermistor for real time monitoring of stator windings' temperature
-sensor bearings to measure rpm (9" models only) or proximity rpm sensors
-forced air cooling.

Why Neutrally Timed Interpoled Motors are Superior Technology:

Kostov has performed tests on an interpoled Kostov 9" 80V motor. One would think that 80V is relatively low and does not justify the use of interpoles. Indeed it may be so for low rpm, low amp forklift motors but the data shows this not to be true for EV conversion motors. For example most good EV motors have more than 4000rpm and 200A. The Kostov 9" 80V usually has collector temperature change of 120K in 60 minutes of work (up to 140K according to standard) at 280A. Removing the interpoles results in temperature change to 157K in JUST 10 minutes. Advancing the brushes by 8/12 degrees improves the number to 147/141K but still in only 10 minutes.

Should the brushed of an interpoled motor be advanced?

The interpoles create a magnetically neutral point whose position is independent of rotation direction, rpm, amps or voltage. The brushes are positioned exactly in this point. Advancing them will result in moving away from the neutral zone and will worsen commutation/arcing drastically. This, in turn, can have very bad consequences for the motor.

How does interpoled motor construction differ from "standard" motors?

The change is in several aspects: 1) The lack of interpoles creates a imbalance above 60-70V; the commutator is very hot while the armature/stator windings are cold. 2) This calls for few bars in the commutator so that the bars can be big to dissipate heat. 3) Few commutator bars call for a much longer armature so that torque/rpm can be reasonable. 4) The result is a long and heavy motor whose commutator is on the brink of melting but armature/stator windings stay uselessly cold. On the other hand, interpoles reduce brush arcing so that commutator temperature falls down. This allows a bigger bar count and shorter armature stack making the motor much lighter than its non-interpoled counterpart. Therefore for a comparable power, an interpoled motor has less weight (20-40%), bigger diameter but much shorter body and the ability to handle high voltage. Less weight means a cheaper motor and of course more range.