GVM - IK-280 trolleybuses

The BKV - Ikarus trolleybuses
IK-200 series prototype trolleybuses
GVM - IK-280 trolleybuses
Obus - IK-280 trolleybuses
Foreign IK-280 trolleybuses

GVM is an abbreviation: meaning Ganz Villamossági Művek (Ganz Electric Works). However, hereafter I will use it as it is done by BKV - referring to the IK-280.93 type articulated trolleybus fitted with chopper control electronics, although there were other constructions of the Ganz factory.

The first IK-280 trolleybus prototype of Ganz (IK-280.T6)

The Ganz Electric Works built two prototype chopper control trolleybuses by 1980, for testing and demonstration. The first vehicle was exhibited on the Budapest International Fair after its trial runs, then it was taken to Leipzig (East-Germany) again for the Autumn International Exposition. Then it was pulled to Weimar, where (between September and November of 1980) it made succesful testruns. In the following year this trolleybus toured Bulgaria, on the expo of Plovdiv, then it made again demonstrational runs in Sofia.

This vehicle had full red liveries, and was fitted with flapping doors, which was unusal at the time. The chassis and the body was similar to the standard Ikarus buses, with minor changes because of the electric parts. Its electronics was significally different from the later series', it was resembling mostly to the BBC prototypes. The simplified plan of the electric circuit can be found here. The most important difference is the lack of the rheostatic brake, instead a separate Eddy-current brake was installed on the motor axle. The trolleybus was fitted with a TK 101 type 150 kW motor, and a 39 kW petrol aggregate being able to run on wireless sections. Also a mechanical trolley puller device was installed.

In 1982, the vehicle was brought to Szeged, where on 19th July, 1984 it was taken in the fleet with the number T6-281. It was in service until the end of the '80s; around 1990 it was hit by a lightning, damaging its electrical parts severely. For a few years the trolleybus was still stored in the depot, until it was scrapped officially in 31st March 1996, and dismantled.
Ganz 1. prototype (Budapest)
Ganz 1. prototype (International Exposition of Leipzig)
The prototype during its trial runs in Budapest, in new state.
At the International Exposition of Leipzig, in East-Germany.
Ganz 1. prototype (en route to Weimar)
Ganz 1. prototype (Weimar)
R. Schindler
The trolleybus was pulled to Weimar by the tractor of the local transportation company.
The trolleybus in Weimar (East-Germany) in 1980, where it obained the licence number LS 15-04.
Ganz 1. prototype (Plovdiv)
Ganz 1. prototype (Sofia)
At the Plovidiv expo, in Bulgaria.
After, it arrived to Sofia, capital city of Bulgaria.
T6-281 (Szeged)
Hans Lehnhard
T6-281 (Szeged)
With already a Szeged fleet number in 1985.
The end: put to the side at the depot in 1993.

The second GVM prototype trolleybus (IK-280.T6/1)

The second prototype GVM was produced for Izmir (Turkey) still in 1980. This one had orange color with a white stripe on the side. After the trial runs in Budapest, the trolleybus was also on tour in Ankara too. Then it was taken back to Budapest, and possibly after some more runs in Budapest in 1982 (?), this vehicle was also supposed to go to Szeged (with the proposed fleet number T5-281). However, instead it went back to the Ganz factory, and was used for experiments of the chopper control in 1984/85 (the other testcari of the factory was the second BBC prototype). After the works, the non-functioning vehicle was taken to Damjanich depot.

In 1990, the empty body was reused by the Obus Ltd., it was fitted with a ZIU-9 electrics (from the parts of DKV 9-310, which had an accident). Indeed on 19th March 1990 this articulated trolleybus was taken to the fleet of Debrecen with the number 400, being the first articulated trolleybus in the East-Hungarian town. (Four similar trolleybuses followed as it is described here.) However the car still possessed its prototype being, many parts were impossible to mend, and its cabels were also a mess. This was the reason, why it was on 25th January 2000 scrapped and taken apart.

The original electrics of the second prototype was similar to the first, except iti already had a rheostatic brake with resistors (without recuperation) regulated by the chopper. So the heavy and unreliable Eddy-current brake device was spared. This trolleybus was also fitted with a 39 kW petrol-aggregate.

Ganz 2. prototype (Pongrác depot)
T. Johannsson
Ganz 2. prototype (Budapest)
T. Johannsson
The second GVM prototype in 1980, at Pongrác depot.
The side of the second prototype, at Örs vezér tere terminus.
Ganz 2. prototype (Damjanich depot)
Ganz 2. prototype (Damjanich depot)
C. Rickert
The empty body of the trolleybus at Damjanich depot, in Budapest.
The rear section in 1988.
DKV 400 (Debrecen, depot)
DKV 400 (Debrecen, depot)
In debrecen in 1993, with the fleet number 400.
Scrapped in 2000. Soon the trolleybus was dismantled.

GVM trolleybuses in East-Germany (IK-280.93)

The first order of the GVM trolleybuses came from East-Germany and Bulgaria. In East-Germany, the city of Potsdam, Weimar, Eberswalde and Hoyerswerda obtained articulated Ikarus trolleybuses.

In this country, by the '70s the whole trolleybus fleet became obsolescent, typically with Skoda 8Tr and 9Tr vehicles with average age of 15 years. Even greater problem was the total lack of articulated trolleybuses, in Eberswalde in 1985 still existe the trailer pulling trolleybus-trains in everyday service. Because of the bad conditions, in Zwickau the local trolleybus service was already stopped in 1979. The situation of the Weimar and Potsdam networks were no better. In this circumstances arrived the first Ganz prototype to the Leipzig exhibition and to Weimar. There the trial runs were succesful, but because of the usage of western equippment in the electronics (which would have cost to the country to spend from the tight western currency) East-Germany was not able to order such vehicles.

Meanwhile the Ganz factory has altered the original equippment, and was able to replace the western parts to the cheaper eastern ones. Also the petrol-aggregate was omitted meaning significant reduction of the price of the trolleybuses. Then East-Germany decided to order 150 IK-280.93 type trolleybuses, of which the first series were delivered in 1985, the second in 1989. The first series was fitted with folding doors, but the second already with flapping doors, which was still at the time unusual in the country. A speciality of these trolleybuses was that they were able to run on every polarity of the poles, which was not the property of the rest of the GVMs.

After the launching of the modernisation programme, three new trolleybus network was built based on the new Ikaruses and Skodas: in Suhl, Hoyerswerda and in Stendal. Because of the central distribution of the new vehicles, some GVMs were moved to another city in few years.

Eberswalde 11
Potsdam 951
The trolleybus 11 of Eberswalde is from the 1985 series.
The trolleybus 951 in Potsdam.
The trolleybus service was abandoned in 1995 in this city.
Weimar 216
Hoyerswerda 715
The 216 of Weimar is already from the 1989 series. The trolleybus is just about to leave the Hauptbahnhof.
The photo was taken in 1992, after one year the service also stopped in Weimar.
Trolleybus 715 in Hoyerswerda, in 1991.
The new trolleybus network was founded in 1989, but abandoned already in 1994.

After the german reunification, the high-floor Ikaruses were not suitable for the stricter European norms. From the originally ordered 150 vehicles, only 55 were delivered. Although at most of the cities the GVMs made a good impression, in the '90s they were doomed to be sold or scrapped. The last of the GVMs were in service in Germany in the town of Eberswalde (the 022 and 025, which were sold then to Szeged, Hungary, with the fleet number 507-506). Meanwhile other East-European countries selected some spare trolleybuses, which were still in good condition. This way the cities of Timisoara (Roumania), Tallin (Estonia), Chelyabinsk (Russia) and finally Szeged (Hungary) obtained GVM trolleybuses.

More about the East-German trolleybuses can be found here.
About Eberswalde GVMs one can read on these pages.
Fleet data

Timisoara 12
Tallin 429
In Timisoara the trolleybus 12 (ex Eberswalde 020).
The trolleybus 429 of Tallin (ex Hoyerswerda 718).
Chelyabinsk 3850
SZKT 507 (Depot)
In 2001, the trolleybus 3850 of Chelyabinsk (ex Weimar 215).
On the GVMs the automatic trolley pulling device was dismantled at the rear. Instead a ladder was inserted.
The 507 in Szeged (ex Eberswalde 022), in 2001.
The replacement of the windows to openable, and the change of the system of the door-closing signal were the major terms of putting them in the service.

Ganz trolleybuses in Bulgaria (IK-280.92)

In Bulgaria, the capitol city Sofia ibought between 1985-91 alltogether 156 (?) GVMs. Also the town Wratsa purchased four articulated vehicles from Ganz. The bulgarian version obtained the type IK-280.92, but the differences and fleet data are unknown to me.
Sofia 1408
Sofia 2705
The 1408 of Sofia in a brand new state.
The 2705 in 1996, in Sofia.
Wratsa 116
The 116 articulated GVM in Wratsa.

IK-260 solo GVM trolleybus (IK-260.T2)

After the Budapest 600 solo trolleybus, in the '80s another solo IK-260 trolleybus was produced. This was fitted with the experimental electronics of the Ganz works. The trolleybus was finished in 1986, and in this year it was exhibited at Leipzig International Fair (East-Germany).
Some technical data:
length: 11000 mm motor type: TK 110-K
width: 2500 mm output: 196 kW
height (with trolleys): 3520 mm seats: 22
weight (without load): 10120 kg standing places: 86
This trolleybus was equipped with the parts of the articulated trolleybuses, thanks to the equal power of the motors, this vehicle was able to accelerate even swifter. Also similarly to the german GVM versions, it was able to run on each polarity.

After exhibition the trolleybus was on trial run in Weimar, where it was bought in the end. There it obtained first the fleet number 8012, then 241. the car was extremely popular amongst the drivers. Meantime East-Germany ordered 12 similar solo trolleybuses for the city of Potsdam with delivery set to 1991, but after the unification the business was cancelled. The unique trolleybus remained in service until 1992, then it was taken back to Budapest by an agent. Here - since nobody wanted to buy it - it was dismantled.

Further informations of this trolleybus can be found on the inofficial site of Ganz.

Ganz IK-260 prototype trolleybus (Budapest)
Ganz IK-260 prototype trolleybus (Pongrác depot)
The solo GVM on a Budapest trial run, at Városliget (City-park).
The trolleybus at Pongrác depot.
Weimar 241
Weimar 241 (Budapest, Reitter F. utca)
Gábor Kelecsényi
In Weimar, in service, in 1991.
After 1992, the trolleybus was brought back to Budapest, to an estate at Reitter Ferenc utca (street). The photo was made there.

The Moscow 0010 GVM prototype

Another demonstration trolleybus was made for the Sowiet Union in 1987. This car made a short trial uns in Budapest, then it was in service with the fleet number 0010 in Moscow. The trolleybus was not long there, after it returned to Budapest. Finally its empty body was set aside at Pongrác depot; the Obus Ltd. was thinking about refurbishing it similarly to the DKV 400. Because of the bad condition of the vehicle, it was rather taken apart.
Moscow demonstrator GVM (Budapest)
Moscow 0010
The latter 0010 in Budapest, on a trial run in 1987. At the time, the side inscription with cyrillic letters were singular in Hungary.
The 0010 in 1987, at the streets of Moscow. The first inscription on the side is replaced with the fleet number, the rest two remained.
Moszkva 0010 (Pongrác depot)
Sándor Krizsán
In 1991, at Pongrác depot, in the "pit" (in the background is the 100).

The GVMs of Budapest: the 200ers.

In Budapest, the first trolleybuses from the GVMs were bought in 1987, after already it was produced in larger quantity to East-Germany and Bulgaria. These cars replaced the earlier 100 series and some part of the ZIU-9 type trolleybuses.
Purcase of the GVMs
number of new trolleybuses
fleet number
The first seven troleybuses had still folding doors, while the rest was supplied with flapping doors uniformly. After the year 2002, the first ones also obtain flapping doors itogether with the necessary reparation works. Today all 84 pieces are in service, there was no scrapping from the already 15 years old fleet. They run currently everywhere the 100ers ran before, today (2002) on lines 72, 75, 77, 79, 81, 82, 83 (except particular cases).
It is interesting, that at the beginning these trolleybuses had their initial technical difficulties, that is why lots of drivers did not like to work with them, instead they would have taken the oldaer 100ers. Nowadays the opposite: peculiarly the drivers like the best from the Budapest types the "good-old" GVMs: these are found the most convinient and trusty cars.

Fleet data

203 (Budapest)
207 (Pongrác depot)
The trolleybus 203 at Fővám tér, in a new state.
The 207 vas the first GVM trolleybus in the BKV's fleet, with flapping doors.
200 (Pongrác depot)
239 (Budapest)
The first Budapest GVM, the trolleybus 200 - in 2001, at the trolleybus depot.
The 239 in March 2000, on line 75, at Könyves Kálmán körút (boulevard), in intense traffic.
263 (Budapest)
On 27th March 1997 a young man has stolen the trolleybus 263 standing out of service at Örs vezér tere terminus. He put the trolleys on the right poles, opened the drivers cabin, started the trolleybus - and hit the first house "blocking" the way.

There were two more hungarian trolleybuses fitted with GVM equippment
First was the BKV 199, about which one can read here. This one became the BKV 283 in 1996.
The second was the second BBC prototype, which was in Szeged from 1987 the T6-282. Further description can be found here.

In 2001, the descendant of Ganz Electric Works, the Ganz-Transelektro has rebuilt the Szeged 502 trolleybus with a brand new three-phase asynchronic motor and electronics. About this here can be found some informations, and also at the inofficial pages of the engeneers.

Technical description of the GVMs

length: 16.5 m constant output: 196 kW
weight (full load): 23850 kg auxiliary motor output: 12 kW
seats: 35 acceleration: 1.3 m/s2
standing places: 110 deceleration with rheostatic brake: 1.2 m/s2
motor type: TK 110 K deceleration with pneumatic brake: 5 m/s2

The structure of the IK-280 trolleybus

The GVM trolleybuses were built in Ikarus body, which is similar to the autobuses. The body is self-carrying, their side walls, roof, roof, windows and doors are all play important role in the stability.

The motor, and the electric equippment is fitted on the cassis, the trolleys, some electronic filters and the brake-resistors are on the roof. The ventillation of the chopper electronics is through a typical side gap on the left side.

Repair works
Zoltán László
One of the GVM trolleybuses during a renewal works, with a stripped body.
The trolleybuses are equipped with hydraulic servo for the steering, which directs the A axle. The B axle is the driven one with double wheels, the largest weight is here. The C acle is on the trailer part, this is also steered proportionally to the bend of the articulation. This gives an excellent steering property to the vehicle, where a solocar can turn, the GVM can pass too.

The car has pneumatic suspension, which gives similar attribute of the running at every load. This makes the driver's job easier, comparing to the ZIUs the derailment of the trolleys are more unlike caused by road irregularities. Some trolleybuses are also equipped with a probe on the level regulation of the suspension, which is used to measure the actual number of passengers. These are called "Knorr"-cars (after the mark of the device).

259 (driver's cabin)
Vitézy Dávid
Driver's cabin of trolleybus 259.
Inside originally the GVMs were fitted with leather seats similar to the last series of the IK-280 autobuses. With renewal works they were changed to textile covered ones, also using digital informational instruments. As interior lights strip lighting was installed.

The doors are pneumatic. The refurbished cars already cannot start with open doors, it is blocked electronically. The windows are also standard Ikarus design, amongst them roof vents are exchanging the air inside.

The trolleybuses have automatic trolley pulling device, which in case of derailment, a spiral arrangement whips off the the trolley. This works good, the only disadvanage is the extra time to put back the trolley on the pole, since the device has to be wound again by hand.

225 (interior)
Zoltán László
Interior of the refurbished GVM 225.

The electronic equippment of the GVM trolleybuses

The GVMs were the first series of vehicle by the Budapest Transportation Company (BKV), which was equipped with (at his time) modern DC-copper electronics. This was consisted of conventional thyristors, made partially in Czechoslowakia and ths Sowiet Union. From a certain point the russian ones were replaced with western, after the running short of the stockpile.
The great advantage of the GVMs were the excellent rheostatic brake with very high recuperation rate; in this sense even the western types are hardly competing with it. This was developped in the first part ogf the '80s, modifying the original plans from the prtotypes. Some other construction of the time even avoided rheostatic brake with the chopper, using Eddy-curent brake instead.

The trolleybuses have motor TK 110 K with the power of 196 kW. The DC-motors with chopper electronics are slightly different from the ones used with resistor controls, having different type of character diagrams.

GVM motor
The motor of the GVM, disassembled.

The simplified electric circuit of the GVM:

GVM main circuit
The GVMs simplified 600V circuit.
On the left are the protecting and filtering devices, together with the auxiliaries. The important electronic side is on the right.
Here follows the main part of the circuit
Part of the motor
  • rotating part (F)
  • standing part (Á)
  • free-wheeling diode (Sz)
  • "brake diode" (Fd)
  • brake resistor (Fe)
  • brake "precursor" resistor (Ee)
  • main tyristor(Ft)
  • shunt tyristor (St)
  • brake resistor tyristor (Fet)
  • brake "precursor" resistor tyristor (Et)

Working in acceleration:

In acceleration the chopper has only one task: to comvert the 600 V DC to a smaller mean value voltage. This is achieved by dense turning on-off the current, this way "chops" the chopper. Regulating the time ratio of the turned on and turned off state one can change the average level of the voltage. The frequency of the coupling is 500 Hz, but in case of too low or too high secodary voltage (in the case when the turned on or the turned off state would be too short) the frequency is dropped to around 70 Hz.
The 500 Hz voice of the chopper can be heard in the trolleybus, the motor, the cables, the chopper and the brake resistors all together emit this.
The main tirystor not completely turns off the current, because it would damage the drive and the chopper too. Instead in this case it makes the motor get in a short circuit (without exchanging the polarity) through the free-wheeling diode.
Near the main tyristor, also the shunt tyristor plays a role: replacing the usual shunt resistor. This weakens the magnetic field of the standing part, causing further acceleration in large speed.
The electronics is regulated with an analog computer. This means, that the adjusment of some accelerating parameters is only possible throug replacing some parts of the electronics (so - unlike the more modern types - it is impossible basically to change them). 

The GVMs have a jerk restriction: by turning on the power the GVMs are calibrated to 0.8 m/s3; by turning off 8 m/s3 secondary acceleration value.

Solo GVM - computer
The analog computer is situated in the first case in front of the first axle on the left.

Rheostatic brake:

The electronics does two phase in one period.
First the motor is in short circuit through the main tyristor with opposite polarity: in this case the current rapidly increases.
In the second phase the excited motor is coupled to the main voltage or to the brake resistors with turning of the main tyristor. Since the motor has an inductive inertia, the current flows backwords to the pole polarity. This way the excitation of the motor also decreases back.
The polarity of the motors are exchanged withe the direction switch contactors. This way the rheostatic brake does not work, when the trolleybus goes backwards.
In case the line voltage goes above 720 V, the brake tyristor automatically directs the current to the resistors. But (if the line contactors does not turn off) the trolleybus feels the possible drop of the voltage, and can restart the recuperation in the same braking process (some other recuperating constructions cannot do the same).
For the stability of the second phase, in case of high speed (above approx. 35 km/h) an extra brake "pecursor" resistor must be coupled serially in the circuit (the other case is would cause blocking of the driven axle). This resistor is regulated with its chopper (some constructions use permanent resistor). The gradual removal of this resistor from the circuit also increases the efiiciency of the brake.

Pneumatic brake:

As on every trolleybus, the main brake is the pneumatic brake. This is regulated with the brake pedal; together with the rheostatic brake. Until the half way of the pedal, the rheostatic brake porvides maximal 1.2 m/s2 deceleration. With further pressing of the pedal, one decreases back the rheostatic brake giving way for the pneumatic brake, with achiving 5 m/s2 deceleration. In case of winter conditions, the rehaostatic brake can be shutted off.
Originally, the trailer's axle is always braked with 0.7 bar pressure even with the rheostatic brake. This is supposed to draw out the trailer part. The BKV have this function disassembled to spare the brake shoes.
All GVMs - as the buses - have anchoring brake, which operates in case of no air pressure. Also in the renewed cars, when the car stops, 2 bar is put in one brake air-circuit, This makes the drivers' job easier, not to hold the car standing with continuous pushing the pedals.


The compressor, the oil-pump of the steering servo and the generator is driven from a common motor of 12 W output ran by 600 V. One has to admit, that this is the most voulnerable part of the GVM's, it is noisy and it brakes down very often especially in the summer heat. This is mainly bacause it operates continuously, and can rech high temperature like that.

The vehicles were fitted with heating system with built in ventillator, it is situated under a seat in the passengers' room.

The auxilliary motor, with a v-belt connection to the pump and the compressor.
The trolleybus is fitted with an automatic point operating system, an extra resistor is coupled in the circuit. In case of switching to the "not-operating" reading, the recuperation is also cease (the back flowing current could also operate the point of the pole).

The direction of the trolleybus is exchanged with four contactors (wich according to the above plan take part in deceleration too).

As we can notice, the electronics is not suitable to operate in case of exchanged polarty. Moreover, the false polarty threatens the electronics, some places the electrolit condensators might blow up in this case. Though these are protected by fuses, but in the beginning the fuses could not react safely in time to avert the damage.


Interesting fact was, that by the order of the first trolleybuses at the BKV, the directory has signed the contract, that on the Budapest network, there is no place where the trolleybuses run on opposite polarty. This was thought to be so, but during the testruns of the GVMs to Bulgaria at some place the trolleybuses misteriously always broke down. Namely at certain blunt angle crossings for a short section (a few 10 cm) the polarity exchanges(!). The vehicle could come through, if everything was shut down, but the most cases it produced malfunctions. After the nature of the problem was discovered, for a few years the engeneers debated to build in a polarity protection, but in the end they rather insulated both directions of such crossings.

However above the polarity exchanges, some more delicate points remained in the network: where the short no-voltage sections are not caused by an insulation, but only the two poles are in the same voltage (i.e. unidirectionally insulated trolleybus crossings, tramline crossings, points). In this cases the recuperational brake could cause sudden problem, when the trolleybuis tries to recuperate in a short-circuit (this is equivalent of having the two poles on the same voltage). In this case using the "no point-operating" switch, the driver can separate the circuit of the trolleybus completely from the poles, without the possibility of automatic shutdown of the electronics.
Further problems occured in the winter conditions with new new copper electronics trolleybuses. Especially in case of sleet the ice can freeze on the pole. Thus the contact of the pole can go wrong. Wirh the ZIUs electrics this meant no great problem, only the trolleybus can start with jerks and great sparks. The GVMs sophisticated electronics is more sensible to such fluctuation of the voltage. In such conditions extra trolleybuses are sent to break the ice from the poles (naturally ZIUs); a former autobus (ex BU 88-41) was converted to a pole-sprinkling car; and the refurbished GVMs are supplied with a ice melting switch. 295 (Pongrác depot)
This trolleybus like thing is actually an autobus, used as a pole-sprinkling car.
In the rear section an extra resistor is placed to make possible to operate the points.

A Ganz prototype circuit on a simplified plan:

The main circuit of the GVM prototype on a simplified plan.
1 - trolley, 2 - overvoltage limiter, 3 - main fuse, 4 - polarity reversing input rectifier, 5 - main contactor, 6 - filter choke, 7 - filter capacitor, 8 - DC chopper, 9 - smoothing choke, 10 -free-wheeling diode, 11 - reversing switch, 12 - traction motor, 13 - fiels weakening resistor, 14 - field weakening contactor
Following the trace of the current we can see, that after the trolley (1) a polarity rectifier circuit follows (4), which made the vehicle able to run on each polarity. After the main contactor follws (5 up) wich (together with its pair) turns on in case of pushing the pedal. The next element is the rotating part of the motor (12 up), which according to the four direction switch (11) can run forwards or backwards. Next the current goes on the standing part of the motor (12 down). Parallel to this the field weakening contactor (14) can couple a resistor (13) in the circuit. The main regulator is the DC chopper (8), which is next. This either turned on, in this case, the current flows back to the negative pole (through the main contactoron (5 down), the polarity rectifier (4) and the trolley (1)); or the copper is turned off, in this case the current goes through the free wheeling diode (10). The operating frequency of the chopper on this trolleybus was around 500 Hz, htis meant 2 msec period of turning on-off. With regulating the ratio of the on-off state, the average voltage of the motor could be changed, thus the output power of the motor was in larger speed interval constant.

The electric (rheostatic) brake is completely missing, this is the main reason why was enough one chopper unit, compare to the GVMs four.

Every comment is welcomed!
Written by: Zoltán Ádám Németh
The author would like to thank Márton Balázs, László Jakab, Mattis Schindler, Marcell Revisnyei, and Tamás Szabó for the help
Part of the pictures originated from Bálint Hajtó, Zoltán László, Dávid Vitézy, and the inofficial Ganz webpage
The homepage of Ganz-Transelektro