Kone elevator 45 kW motor drive teardown

This is a Kone KM997160 variable frequency motor drive that is developed and used for elevators. 

Kone has a long history of their own motor drives that came in more or less atypical enclosures compared to other variable frequency drives. With this KDM model, they do however take the same form as many other drives by other manufacturers, which could lead to the assumption that these are made by a contractor and are just controlled by Kone’s own software and safety systems.

In the following pictures we see the complete unit that is about 1 meter tall and weighs somewhere around 70-80 kg. Full plastic front without any form of interactive interface or display, just 3 status LEDs that shows power, error and running.

From the specifications sticker on the side, we get the following information:

Input: 400V, 3~AC, 50-60Hz, 71A

Output: 0-Uin, 3~AC, 0-250Hz, 90A

Power: 45kW: 400V / 60HP: 400V

Taking a look under the hood we first see the DC bus capacitors at the top, the gate drive control board and underneath the black plastic cover we find the CPU.

The 4 identical metal plates that can be seen is the mounting plates for the SKiiP IGBT modules. The 6 red boxes with wires going through is the current transformers and the wires with yellow cable shoes goes to the chokes underneath the power electronics.

Two of the IGBT modules are used for AC to DC input stage with active power factor correction. The last two IGBT modules are used for outputting the variable frequency supply for the motor. The two large capacitors at the top are for the DC link.

Altera Max II EPM240/G/Z  is a low cost CPLD with 240 logic elements, 80 user defined I/O and 8kb of memory available at a internal clock frequency rate up to 300 MHz.

Atmel AT91SAM9260 ARM-based Embedded MPU. 180 MHz ARM processor with 8 KBytes Data Cache and 8 KBytes Instruction Cache. 

Semikron SKiiP 39AC126V2 IGBT module, a 3 phase bridge inverter module developed specifically for use in motor drives up to 45 kVA / 30 kW. Two of these modules are used in parallel or interleaved in this motor drive to reach its rating for a 45 kW motor.

It is a 1200 VDC module with a continues rated current at 157 Ampere, with pulsed currents up to 280 Ampere. A very fast module with a combined switching on/off time of only 720 ns. The SKiiP packages are however a pain in the ass to salvage from equipment where they are stuck to the heat sink through sticky compounds. When the screw, holding the IGBT and contact points in place, is removed, then there is only the thin aluminium bonding wires keep the silicon chips together with the enclosure, and these breaks very easily as if can be seen in the pictures.

The power factor correction choke and output chokes from Epcos are all mounted in a tray and have been wholecasted in blue epoxy, which pretty much makes it impossible to salvage for use in something else and not even the cores are possible to get free in one piece. The filter assembly is rated for 480V at 76A.

The two DC link capacitors 70CPE00150 from Kemet at each at 700 uF and 800 VDC. I have not been able to find a datasheet for these, but a guess from their physical size compared to other Kemet DC link capacitors and the ratings of this motor drive, they are properly good for about 50 A RMS each.

About Mads Barnkob

Electrician, experimenter and amateur scientist with experience in industry automation, programming and all kinds of high voltage generating electronics.
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