Abstract: To provide a single-phase induction motor control method and apparatus and an electric chain block which are capable of appropriately judging an overload of a single-phase induction motor even when the single-phase induction motor is in a condition where energization of an auxiliary coil is repeated. Provided is a method of controlling a single-phase induction motor including a main coil ML, an auxiliary coil AL, a capacitor C. and an SSR (solid-state relay) power circuit 121, in which the main coil ML is supplied with an electric current from a single-phase alternating-current power supply 200 through the SSR power circuit 121, and when the load is heavy, the auxiliary coil AL is energized. An overload is judged based on the ratio of energizing time during which the auxiliary coil AL is energized within a predetermined time.

Abstract: An upper and lower limit detecting apparatus and method for a load suspending device of an electric chain block capable of easily and rapidly detecting reaching of the load suspending device to a lower limit without providing a lower limit reaching detection limit switch. In an electric chain block including electric motor, friction clutch, electromagnetic brake, speed reduction gear mechanism, load sheave, load chain, load suspending device, etc., the reaching of the load suspending device to the upper limit is detected by an upper-limit reaching detection limit switch, and the reaching of the load suspending device to the lower limit is detected by judging, with an electric power type overload limiter, that the power consumption of the electric motor has exceeded a predetermined value as a result of a stopper abutting against a chain guide and the friction clutch being dragged by rotational force of the electric motor.

Abstract: To achieve a size reduction by on-off controlling non-contact switching devices with a microcomputer. When a three-phase alternating-current electric motor is to be used, lead wires of the three-phase alternating-current electric motor are connected to output terminals of a control board. When a single-phase alternating-current electric motor is to be used, two supply terminals of the control board are electrically connected together through a first connecting member, and one end of the first connecting member is defined as a single-phase alternating-current power supply terminal. A second connecting member is connected to a supply terminal, and one end of the second connecting member is defined as a single-phase alternating-current power supply terminal. A main winding of the single-phase alternating-current electric motor is connected to the output terminals, and an auxiliary winding is connected to the output terminal and the second connecting member.

Abstract: To achieve a size reduction by on-off controlling non-contact switching devices with a microcomputer. When a three-phase alternating-current electric motor is to be used, lead wires of the three-phase alternating-current electric motor are connected to output terminals of a control board. When a single-phase alternating-current electric motor is to be used, two supply terminals of the control board are electrically connected together through a first connecting member, and one end of the first connecting member is defined as a single-phase alternating-current power supply terminal. A second connecting member is connected to a supply terminal, and one end of the second connecting member is defined as a single-phase alternating-current power supply terminal. A main winding of the single-phase alternating-current electric motor is connected to the output terminals, and an auxiliary winding is connected to the output terminal and the second connecting member.