The Company's Products

This section contains details of some of the many and varied products that were produced by the company from the early 1900s to the 1940's. At this time the principal products were rotating electrical machinery, switch and control gear, static transformers, and rectifiers.

 

Two motor starting switches from 'The Engineer' 25th August, 1911.

 

An air break switch and a liquid resistance switch from 'The Engineer' 1st September, 1911.

An advert from 1920 showing an E.C.C. motor driving a steel rolling mill.
One of E.C.C.'s larger DC motors. It was installed at a rolling mill and operated in conjunction with a steam-turbine driven generator.

The motor was rated at 5,000 bhp., at 55 r.p.m. It was reversible and could reverse direction from full speed in one direction, to full speed in the opposite direction, in seven seconds. The speed could be adjusted by varying the current in the field windings. The maximum speed was 110 r.p.m.

Two synchronous three phase 600 bhp. motors, that were used to drive air compressors in a colliery.

The motors also provided power factor control, so that the equipment operated at its greatest efficiency.

Part of a large installation at a spinning mill.

The squirrel cage motors were capable of delivering 10 bhp., and were driving ring-spinning frames.

The company produced switchgear to control all types of AC and DC motors and generators.

Some of the switchgear, called "trucks" was mounted on wheels to allow easy access.

The photograph shows part of 60 high tension "trucks" that were installed in a metropolitan borough power station, to control the outgoing supplies.

The E.C.C. built all types of transformers, up to 10,000 KVA.

The photograph shows a 10,000 KVA unit of the outdoor type, with a conservator and oil-cooling radiators.

A 2,200 volts, 65 kW rectifier unit, using two mercury arc rectifiers, oil-cooled transformer and D.C. switchgear.

It was built for a Corporation electricity department and delivered an output of 220 volts D.C. at 65 kW.

A small metal-plate rectifier unit that was built for a Government department and used to supply a wireless telegraph communications system.
The equipment opposite was installed in a steel works. It consisted of a 500 bhp. motor, with a speed range of 150 to 350 r.p.m., a 750 kW rectifier unit, which provided 480 volts D.C., from a three phase A.C. input, of 5,500 volts. There was also a second motor that was rated at 350 bhp. The control switchgear is on the right.
An E.C.C. patent varispeed drive, applied to a machine tool. It consisted of a mercury arc rectifier, variable speed D.C. motor, and the necessary control gear.
The following article about the E.C.C. 'Varispeed' system appeared in 'The Engineer' on 8th November, 1946:

A Variable-Speed Power Drive

The problem of providing variable-speed power drives is of considerable interest, not only because it affects an ever-increasing number of manufacturing processes, but because the solution involves a choice between many methods, both mechanical and electrical.

Amongst the more common electrical methods of obtaining a variable-speed drive are change pole induction motors, Ward-Leonard sets, AC. commutator motors of various kinds, and, where a DC. supply is available, the shunt-controlled DC. motor. Because of its excellent speed characteristics, the shunt-wound DC. motor commends itself to many engineers, but its use nowadays tends to be restricted because of the modern preference for individual drives in production machines, coupled with the adoption of standard three-phase AC. supply throughout this country.

Particular interest therefore attaches to the "Varispeed" drive developed and manufactured by the Electric Construction Company, Limited, Bushbury Engineering Works, Wolverhampton, using a standard DC. motor supplied from AC. mains through the medium of a mercury arc rectifier. The rectifier supplies DC. separately to the armature and field system of the motor, the two supplies being independently variable. By this arrangement the speed can be varied over a very wide range, as much as 1000 to 1, providing constant torque throughout this speed range.

A simple single-phase circuit, illustrating the principle of the system, is shown in the accompanying diagram, in which the AC. supply is connected to the primary of a transformer having two secondary windings. The main secondary winding supplies the two main anodes of a mercury arc rectifier, which converts AC. to DC. for supplying the motor armature. The auxiliary secondary winding is connected to two auxiliary anodes to provide DC. for the motor field.

A maximum speed range of about 4 to 1 can be obtained from a DC. motor of normal design by varying the shunt field current while keeping the applied armature voltage constant. Under these conditions the output horsepower remains approximately constant throughout the speed range, for the torque falls as the speed increases, that is, as the field current is reduced.

If, on the other hand, the shunt field current is kept constant while the armature voltage is varied, the speed of the motor varies approximately as the applied armature voltage. By varying the voltage supplied to the armature from zero to maximum, an infinitely great speed range can be obtained with constant maximum torque from the motor, since the field current remains at its maximum at all speeds. Maximum horsepower is therefore developed at maximum speed.

Since the majority of drives require maximum horsepower at maximum speed, with the torque remaining constant at its maximum value throughout the speed range, it is usual to use armature control, which considerably reduces the overall size of the motor. A further reduction in cost results from the fact that armature control normally eliminates the necessity for separate starting gear. The speed control gear can be used to start the motor smoothly from rest. A combination of armature voltage and shunt field control can be applied with advantage in many instances where maximum torque is required at some speed less than full speed, or where some compromise between constant torque and constant horsepower is required.

Assuming, however, that the field is maintained constant, the motor speed will depend upon the armature voltage supplied from the rectifier valve. This voltage can be varied by anyone of several methods, depending entirely upon the kind of drive and the speed range required. Since the ratio of the DC. voltage to the AC. voltage of the rectifier is fixed, a variable DC. voltage can only be obtained by applying a variable AC. voltage to the rectifier. In general, there are three methods whereby the AC. and therefore the DC. voltage can be controlled.


An E.C.C. 'Varispeed' drive for a draw bench.

The first method requires an on-load tap-changing switch to vary the main secondary voltage from the transformer in a predetermined number of fixed steps. The second method employs an induction regulator to vary the main secondary voltage smoothly over a range designed to suit the speed range of the motor.

The third method makes use of grid control between the anodes and cathode of the rectifier, giving smooth control over the DC. output voltage and the speed of the motor. Normally the first method is used for small machines, where a number of fixed speeds is acceptable. With larger machines, when smooth speed variation is important, either of the remaining two methods can be used.

There are therefore three essential components in the equipment; the transformer and controller, the rectifier cubicle, and the motor itself. All of these components can be mounted separately, which allows considerable flexibility in layout. Wiring is reduced to a minimum, since there are only three wires between the rectifier cubicle and the motor (without any intervening starter), and the fine wiring between the rectifier cubicle and the controller.

A typical "Varispeed" installation is depicted in the accompanying engraving, which shows a 267 hp. shunt-wound DC. motor driving an automatic draw bench. The rectifier cubicle and the transformer can be seen behind the main motor. This equipment, which is entirely automatic, gives the motor a speed range of 0 to 1200 rpm. providing constant torque throughout this range. An interesting point is the use of a forced ventilating system which accounts, in part, for the small size of the variable speed motor.

Since acceleration is completely smooth throughout the speed range, the accelerating time can be reduced to a minimum. The system lends itself satisfactorily to automatic control, reversing duty, dynamic braking, and rapidly variable acceleration. Throughout the speed range the efficiency and power factor of the system are high. It will be noted that the rectifier has no excitation losses, since the excitation is used to supply the field of the motor, resulting in an appreciable gain in efficiency.


Assembling motors in 1938.


Assembling transformers in 1938.


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