ER2 electric trainset

The ER2 trainset consists of 2-car sections, each of which includes a power car and a trailer (either a driving trailer with an engineer's cab on one end, or an intermediate trailer without an engineer's cab). Sections with a driving trailer are called head sections; those with an intermediate trailer are called intermediate sections. The sections cannot operate independently; the minimum train length is 2 head sections, and the maximum is 6 sections (2 head sections and 4 intermediate sections), with a train 5 sections long (2 head and 3 intermediate) considered standard. Coupling more than 6 sections is unsafe due to overloading of motor-generators which power the engineer's controls. The cars are coupled together with the SA3 coupler, which is standard on Soviet rolling stock and allows vertical movement of up to 100 mm.

To maximize passenger accommodation, almost all electrical equipment is mounted either on the roof (pantograph) or under the car floors (starting resistors, compressors, etc.) All underfloor equipment is enclosed in cabinets with removable spring-latched access panels to protect it from blowing dust and snow. Some of the auxiliary equipment (including some high-voltage equipment such as the electric meter) is placed in cabinets inside car vestibules. Control equipment is concentrated in the engineer's cab. Numerous changes were made during the production run (see below), which caused variations in equipment layout.

Specifications (for a standard 10-car train): Overall length: 201.81 m Empty weight: 470-484 t Number of seats: up to 1050 Traction motor 1-hour rating: 4000 kW Tractive effort: up to 26,350 kilograms-force Maximum speed: 130 km/h (130 km/h (81 mph)) Acceleration up to 60 km/h (37 mph): 0.6-0.7 m/s² (0.6–0.7 m/s² (2.0–2.3 ft/s²))

Most of the cars' interior space is taken up by the passenger salon. The majority of the floor space is occupied by bench seats, above which are mounted luggage shelves and coat hooks. The bench seats usually seat 6 passengers (3 facing front, 3 facing rear) and are placed on either side of a central aisle. The total number of seats was often varied during the production run; also, during overhauls some of the seats were often removed to increase the amount of standing room and thereby the total passenger capacity. Intermediate trailer and power cars typically have 107-110 seats, and driving trailers 77-88 seats; a 10-car train has up to 1050 seats in all and a total passenger capacity of up to 1600 people. The passenger salon is separated by sliding double doors from vestibules on either end of the car, which have pneumatically-operated sliding double doors for entry and exit of passengers.

Lighting is provided by ceiling lamps with incandescent bulbs (nowadays usually replaced by fluorescent lighting or LEDs); the passenger salons of intermediate trailers and power cars normally have 20 ceiling lamps, those of driving trailers 16, and vestibules 2 each. These lamps are powered by the motor-generators (see below), so if this fails, all lights in the 2-car section go out; to prevent the section from being completely darkened, some of the ceiling lamps include an emergency light which consists of a low-powered incandescent bulb next to the main light, and draws its power from the storage battery.

Ventilation is accomplished partly by opening the windows, and partly by a forced-air system served by 2 twin centrifugal fans. The fans are mounted above the ceiling of each vestibule and force fresh air into a ventilation duct which runs above the ceiling along the car centerline and feeds the air into the passenger salon via a series of small vents. In the summer the air is taken in through outside air intakes and passed through screen filters; in the winter the air is partially recirculated. Heating is provided by electric heating under the bench seats (intermediate trailers and power cars usually have 20 furnaces, driving trailers 14). Each furnace uses 1 kW of power; the voltage feed is 750 V (from the traction power supply), so the furnaces are mounted in electrically grounded outer casings for safety (2 furnaces in each casing). Each heating circuit has 5 furnaces connected in series and fed directly with 3000 V current from the traction circuits.

As on the ER1, the ER2 car bodies are of a welded all-metal semi-monocoque load-bearing design (the entire car body bears all structural loads). The framework is built up from bent and extruded steel profiles, and consists of ring frames which are covered with corrugated sheet steel 1.5-2.5 mm thick. The automatic couplers and their shock absorbers are mounted on short spine beams at each end of the car. The doors and wire conduits are made of aluminum, which helped to keep the weight down and resulted in the cars being only slightly heavier than those of the ER1. Footboards are fitted under the outside of each door for boarding and alighting to/from low platforms; when boarding/alighting passengers to/from high platforms, these are covered by metal aprons (gap fillers). The end bulkheads of each car (except for the head end of the driving trailer, which is occupied by the engineer's cab) incorporate swing-down transfer platforms which allow passengers to walk between cars; these also damp the cars' pitching motion when the train is moving. The cars are 19.600 m (64 ft 3.7 in) long and 3,480 mm (11 ft 5 in) wide. The power cars weigh 54.6 tonnes (53.7 long tons; 60.2 short tons), the driving trailers 40.9 tonnes (40.3 long tons; 45.1 short tons), and the intermediate trailers 38.3 tonnes (37.7 long tons; 42.2 short tons).

Each car is mounted on the bolsters of 2 double-sprung 2-axle trucks; the trucks of the power and trailer cars have significant differences. The power car trucks have axlebox guides which prevent any lateral or longitudinal movement of the axles relative to the truck frame. The truck frame's longitudinal beams are reinforced in the middle to take the car's weight via the bolster and suspension springs. The transverse beams have a complex shape to accommodate the traction motors (which are mounted entirely on the truck frame). The truck frame rests on the axleboxes via the axlebox suspension, which consists of 4 coil springs per axlebox (2 on each end of each axle). In turn, the truck frame bears the weight of the bolster via the double central suspension; the bolster bears the weight of the car directly. The truck frame is additionally reinforced at the attachment points for the suspension swing links. On early trains, the central suspension incorporated elliptical leaf springs, but from 1965 onward they were replaced with coil springs, which increased the maximum suspension travel from 95 to 120 mm (which reduced the risk of bottoming). Both stages of the suspension incorporate shock absorbers: the axlebox suspension has 2 friction shock absorbers per axle, and the central suspension has 5 hydraulic shock absorbers (on trucks with coil springs only). The car body rests on skid pads on the cast side flanges of the bolster; these skid pads are made of layered plastic, and serve to reduce the rolling and yawing movements of the trucks and car bodies. The car body is also connected to the center of the bolster by means of the central pivot—a vertical steel rod mounted in the center of the bolster, which transmits the traction and braking forces from the truck to the car body, and also receives part of the car body's weight.

On the trailer cars, the trucks are similar to those of ordinary passenger cars, but have shorter frames. They lack axlebox guides (the longitudinal movements of the axles relative to the truck frame are limited solely by the suspension springs themselves), the springs are softer, the central pivot is made of 3 segments (which gives it a degree of flexibility), and the axlebox suspension friction shock absorbers are mounted inside the springs (on the power car trucks, they are mounted outside). The leading truck of the driving trailer has brackets for mounting the cab signal receiver coils. The early ER2 trailer cars had KVZ-5/E type trucks (identical to those on the ER1); later examples had the KVZ-TsNII/E type. The latter had the following design changes: the springs were softer; the bolster was attached to the frame by means of 2 swing links with rubber/metallic elements; the weight of the car body was borne by the bolster only via the skid pads (on the earlier type, part of the weight was also borne by the central pivot).

The powered axles of the ER2 trainset are individually driven: each axle is powered by its own traction motor, which is connected to the axle by a pair of spur gears with a torque ratio of 3.17 (73:23) in a fully enclosed gearbox. The large gear with a transmission modulus of 10 is mounted directly on the axle, whereas the small gear is on a shaft which is mounted on 2 ball bearings (on early trains) or roller bearings (on later trains). The gearbox casing is mounted on the axle by means of a sealed roller bearing, and is also attached to the truck frame via a special suspension. Initially this suspension comprised a sickle-shaped link with 2 rubber and metal shock absorbers, but beginning in 1969 this was replaced by a vertical rod with 4 such shock absorbers (as on the ER22). During motion of the train, the frame-suspended motors constantly move relative to the axles, which requires some kind of flexible drive to accommodate this motion. On early ER2s this was achieved by means of a jaw coupling between the motor shaft and the intermediate drive shaft, but on later trains, rubber rag joints were used instead. The first such joint was fitted to an ER2 in 1964 as an experiment; in late 1965, five more prototypes with rubber couplings were built, and from 1966 onward these became standard on all new ER2s.

On power cars, spoked wheels with separate steel tires are used; the tires have an outer diameter of 105 cm (1,050 mm (41.34 in)) and a thickness of 75 mm. The tires are shrunk onto the wheels, which are in turn shrunk onto the axle. One of the wheels on each axle has an elongated hub, which is attached with bolts to the large spur gear. The wheels of the trailer cars are smaller in size (only 95 cm in diameter), solid, have shorter hubs and a thinner axle.

The electrical equipment on the ER2 multiple units is similar to that of the late-model ER1s. Each power car has 4 traction motors connected in a series-parallel connection. The traction motor clamp voltage is controlled by means of starting resistances, as well as by changing the motors' connectivity and by field weakening. They are protected from electrical surges by various protective units: a fast-acting circuit breaker, an overload relay, a differential relay, etc. Early units also had a fuse in the traction motor circuit, but later units had more reliable protective equipment, which led to the fuse being removed as redundant.

The engineer's controller has 18 starting notches, of which only 4 are classified as running notches (allowing prolonged operation of the motors in this notch). Acceleration is mainly controlled by means of resistances which are initially connected into the traction motor circuit and then incrementally notched out by means of shorting with special contactors. These contactors (19 in all) are grouped together in one drum controller. The ER2 uses an indirect control system: the engineer only has to place his (or her) controller handle in the desired notch, and the control system automatically notches out the drum controller to reach that notch. (The drum controller is pneumatically operated). For slow movement, as when shunting, the engineer places the controller in the first notch, designated M ("manevrovoe", i.e. "shunting"); this closes both line contactors, the bridge contactor, and contactors #7 and #8, connecting all 4 traction motors in series and engaging all of the starting resistances (total resistance 17.66 ohm). Moving the controller handle to the next notch (running notch #1) initiates an incremental notching-out (shorting-out) of the starting resistances; unlike most Russian electric locomotives, on which the engineer directly controls the selection of the starting notches, in the ER2 the intermediate starting notches are switched automatically by means of an accelerating relay which regulates the train's acceleration (by monitoring the traction current's change, see also: Traction motor#Automatic acceleration), although the engineer can override it and select the intermediate notches manually. In starting notch #9, all of the starting resistances are shorted out, and only the series-connected traction motors remain in the circuit, their fields at 100% strength. This corresponds to running notch #1 on the engineer's controller. Further notching out of the controller weakens the traction motors' field: in starting notch #10, the field strength is reduced to 67%, and in starting notch #11 to 50%. Starting notch #11 corresponds to running notch #2 on the engineer's controller.

To accelerate the train still further, the traction motors are reconnected in series-parallel connection (2 parallel circuits with 2 series-connected traction motors in each). For this purpose, in starting notch #12 the controller closes a pair of parallel contactors and opens the bridge contactor. After this the controller moves to starting notch #13, which closes contactors #1 and #2 and opens both field-weakening contactors; this assembles 2 parallel circuits, each of which comprises 2 traction motors and a group of starting resistances connected in series and has a total resistance of 4.97 ohm. Further notching out of the controller shorts out the starting resistances in pairs until in starting notch #16 all of the starting resistances are shorted out; this corresponds to running notch #3 on the engineer's controller. Moving the controller to starting notch #17 weakens the traction motor field to 67%, and in starting notch #18 the field is weakened to 50%. Starting notch #18 corresponds to running notch #4 on the engineer's controller; this is the maximum notch and allows the train to reach top speed. To coast, the engineer moves the controller handle to 0; this opens the line contactors, thereby shutting off all power to the traction motors, and moves the controller into starting notch #1 (therefore if the traction motors are turned on again, they are connected in series and all the starting resistances are in the circuit).

The traction motors are mounted on the truck frames (see above), which protects them from impact when rolling over rail joints and reduces the train's unsprung weight. The first ER2s had the same DK-106B traction motors as the ER1; these were DC series motors (the armature and field windings were connected in series, as is normal for variable-speed DC motors) with 4 main and 4 auxiliary poles and wavy armature windings. The motor's clamp voltage was 1500 V, and the insulation was designed for 3000 V (which gave a 2-fold safety margin). Unlike locomotive traction motors, these motors normally operated in weak field, with maximum field strength used only during acceleration. The motors are self-cooling (the cooling fan is fixed on the motor's output shaft); the cooling air is taken in through air intakes above the passenger doors.

In the 1960s, the Riga Electric Machinery Plant developed a new type of traction motor, the URT-110, which had similar performance to the DK-106B. These became standard on ER2 trainsets from March 1964.

Electricity from the overhead contact wire is picked up by the train through pantographs mounted on the roofs of the power cars. These are pneumatically operated, so if the pressure in the air pipe falls below a preset level, they are automatically lowered by means of springs (this prevents the train from moving if air pressure is lost, an important safety feature). Each power car has only 1 pantograph, because if it fails the other power cars can produce sufficient power to move the train at a reduced speed. For the same reason, there is no provision for cutting out individual traction motor groups in case of malfunction, so if even one traction motor fails, the entire power car's traction motor circuit is turned off (the other power cars can still provide enough power, so despite this the train can, and sometimes does, remain in service).

Protection of traction motors from short circuits is accomplished by means of a fast-acting circuit breaker, which disconnects the traction circuit within 2-5 milliseconds if the current exceeds 575±25 amps. In case of a short to ground where the current does not exceed this level, protection is accomplished by a differential relay which compares current at both ends of the circuit and opens the circuit breaker if the difference in current exceeds 40 amps. The traction motors are also protected by a wheelslip relay which trips if the angular velocity of one of the traction motors significantly differs from the others (wheelslip, skidding, stripped gears, etc.) and an overload relay which trips if the current in a traction motor's circuit exceeds 265 amps; tripping of these relays automatically reduces the train's acceleration. The engineer's instrument panel has warning lights which illuminate when any of these relays trip (except for the differential relay—its action can be deduced from certain peculiarities in the tripping of the circuit breaker), and the tripping of the wheelslip relay also activates a warning bell.

To protect maintenance workers from electrocution, all high-voltage cabinets have safety switches which automatically lower the pantograph if the cabinet is opened while the power car is energized. Late-model ER2s also feature a ladder blocking relay which prevents the extension of maintenance ladders when the pantograph is raised, thus preventing workers and bystanders from climbing onto the roof. For passenger safety, all doors are equipped with position sensors which notify the engineer whether all doors are shut (however, in practice it is standard operating procedure for the fireman to step out onto the platform and check the doors visually).

Other protective equipment includes the voltage relay (which trips if the voltage in the high-voltage circuit falls below 2400 V), the dynamotor/compressor overload relay, the heating circuit overload relay, and the automatic control shutoff switch. This last shuts off the traction motor controls when the air pressure in the brake pipe falls below a preset level, which prevents the train from starting with inoperative brakes.

In ER2 electric trainsets (their numbering starts with 300) DK-604B dynamotors, BVP-105A-1 fast switches are installed. These switches have diafragmatic lead. 40KN400 alkaline batteries are used instead of acid batteries.

It is necessary to point out the following from the most significant construction improvements.

In electric trainsets released in 1965 N. E. Galakhov's amortizers are changed by cylindrical springs. The same time hydraulic amortizers are installed between trolley frame edges, and upper beam above the amortizer. The static deformation of amortizing system is increased from 95 mm (3.74 in) up to 120 mm (4.72 in). The body weight is transmitted to improved trolleys through edge sliders, while ______ serves only for transmitting horizontal forces.

In 1964 one electric trainset was released with rubber clutches instead of ______ clutches between shafts of motor and speed reduction couple. By the end of 1965 five more trainsets with such clutches were released.

In 1964 URT-110A traction engines had been installed on electric trainsets. (unified traction engines from Riga) In difference of DK-106B engines collectors are plastic, the isolation of coil, electrode, and rotor is made of escapon. Brush holders are plastic. The electromechanical features of motor remained the same.

In 1965 due to installation of more stable pantograph isolators (made of plexi glass AG-4), the relay system developed by N. A. Lapin was excluded from trains' construction.

In 1963 one of electric trains (ER2a-413) was released with "auto-engineer." It entered Moscow - Klin segment of October railroad for experimental testing.

While speed reduction ratio is 1:3.17, wheel diameter is 1,050 mm (41.34 in), and electric engine clamp voltage is 1500 volts, ER1 and ER2 electric trainsets have following traction data:

The speed is __ km/h, the traction force is __ kg, increased field - 51.8 5270, normal field 71.2 4040. In long timing mode increased field - 59 3530, normal field 82.4 2790.

In case of a 2.5 km (1.6 mi) distance between stops the speed is up to 95 km/h (59 mph). In case of 5 km (3.1 mi) - 110 km/h (68 mph). The minimum radius of curvature is 100 m (328 ft) at a speed of 5 km/h (3.1 mph).

In 1966-1975 period the railcar manufacturing plant of Riga continued the release of ER2 suburban electric trainsets, for 3000 V DC. They started to be built already in 1962. Basic electric equipment for these trains was manufactured by Electric Machinery plant of Riga. The majority of electric trainsets was released in 10 car versions (five countable sections), part in 8-car edition (four countable sections). The separate section edition was accepted too. (?) Electric trainsets can be used in 12-car, 6-car, as well as 4-car compositions. Railcars' length is 20.10 m (65 ft 11 in) including auto-couplers.