GB267777A - Improvements relating to electrical apparatus for the testing of internal combustionand other engines - Google Patents

Abstract

267,777. Highfield, F. W., and Highfield Electrical Co., Ltd. July 21, 1926. Dynamometers, rotary-absorption.-Relates to apparatus employing a dynamo electric machine which can be used as a motor or as a generator and consists in the employment of a pair of such machines mechanically coupled together and capable of being connected in series or in parallel. The engine to be tested, under a system similar to that described in Specification 229,427, is connected to one end of the common shaft of the coupled dynamo-electric machines. In Fig. 2, the machines are shown connected in series, which connection is suitable for moderate speeds when working as motors or dynamos. They are connected in parallel for higher speeds by a single quick-acting switch, the change-over being effected by hand or automatically. In the circuit of the armatures e, f are arranged controlling resistances g, a wattmeter r, a relay h indicating the maximum current, a differential relay i to operate a device indicating whether the machine is acting as a motor or generator, a switch j to break the circuit when required, and a relay k to indicate the maximum load. When acting as generators, the energy is absorbed in a local circuit m by closing the switch l after the switch j is opened. The overload device n trips the switch j on overload. Rheostats w, x serve to regulate the field windings u, v. When the engine is driven by the motors, a relatively small current is required even with all the resistances g cut out, but when used as a generator a large current is required. For the overload device to work under both conditions a number of the turns of the overload relay are short-circuited by the arm q engaging a tapping p when the machine operates as a generator. A diagram of the machines connected in parallel is also included in the Specification.