Load power reduction control and supply system

A power control unit for connection between a source of power and a load, for control of power supplied to the load, which source when connected to the power control unit provides current to the power control unit at an input voltage level, the power control unit comprising:

• an autotransformer connectable to the power source, the autotransformer having a winding tapped at a first output tap for providing a high output voltage level and at a second output tap for providing a low output voltage level, an input tap positioned between the said output taps and connected to a first input terminal for connection to the power source, and the zero voltage point of the winding connected to a second input terminal for connection to the power source and to a first load connection terminal;
• two pairs of inverse parallel silicon-controlled rectifiers, one pair connected between the first output tap and a second load connection terminal and the other pair connected between the second output tap and the second load connection terminal;
• a controller connected to the gates of the silicon-controlled rectifiers for controlling the silicon-controlled rectifiers to set the output voltage level at which the output current is for the time being supplied to the load, the controller controlling the silicon-controlled rectifiers to set a high output voltage level so as to supply power at a set high power setting for a period of time THi starting upon the occurrence of a high power start condition and ending upon the occurrence of a high power end condition and to set a low output voltage level so as to supply power to the load at a set low power for a later period of time Tlo starting upon the occurrence of a low power start condition and ending upon the occurrence of a low power end condition;
• and
• a sensor of current supplied to the load,
• the controller during a transition period following time period THi and preceding time period TLo controlling the gates of the silicon-controlled rectifiers to set a series of transitional output voltage levels diminishing controllably from the set high output voltage level to the set low output voltage level in a series of stepwise decreasing output voltage levels, each stepwise reduction of less than the specified percentage, and each stepwise reduction applied when the current supplied to the load has stabilized.

A power control unit for connection between a source of power and a load, for control of power supplied to the load, which source when connected to the power control unit provides current to the power control unit at an input voltage level, the power control unit comprising:

• an autotransformer connectable to the power source, the autotransformer having a winding tapped at discrete first and second input taps, an output tap positioned between the said input taps and connected to a first load connection terminal, and the zero voltage point of the winding connected to a first input terminal for connection to the power source and to a second load connection terminal;
• two pairs of inverse parallel silicon-controlled rectifiers, one pair connected between the first input tap and a second input terminal for connection to the power source and the other pair connected between the second input tap and the second input terminal for connection to the power source;
• a controller connected to the gates of the silicon-controlled rectifiers for controlling the silicon-controlled rectifiers to set the output voltage level at which the output current is for the time being supplied to the load, the controller controlling the silicon-controlled rectifiers to set a high output voltage level so as to supply power at a set high power setting for a period of time THi starting upon the occurrence of a high power start condition and ending upon the occurrence of a high power end condition and to set a low output voltage level so as to supply power to the load at a set low power for a later period of time TLo starting upon the occurrence of a low power start condition and ending upon the occurrence of a low power end condition;
• and
• a sensor of current supplied to the load,
• the controller during a transition period following time period THi and preceding time period TLo controlling the gates of the silicon-controlled rectifiers to set a series of transitional output voltage levels diminishing controllably from the set high output voltage level to the set low output voltage level in a series of stepwise decreasing output voltage levels, each stepwise reduction of less than the specified percentage, and each stepwise reduction applied when the current supplied to the load has stabilized.

A power control unit for connection between a source of power and a load, for control of power supplied to the load, which source when connected to the power control unit provides current to the power control unit at an input voltage level, the power control unit comprising:

• an autotransformer having a winding separately tapped at
• a first output tap corresponding to the high output voltage level,
• a second output tap corresponding to the low output voltage level,
• a plurality of taps intermediate the first and second output taps and corresponding to transitional output voltage levels intermediate the high output voltage level and the low output voltage level, and
• an input tap positioned between the first output tap and the second output tap and connected to a first input terminal for connection to the power source,
• the zero voltage point of the winding connected to a second input terminal for connection to the power source and to a first load connection terminal;
• a set of triacs, each triac connected between a discrete tap and a second load connection terminal, the triacs individually responsive to control by gate signals provided by the controller so as to selectably supply output current to the load at a selected one of the high, the low, and the transitional output voltage levels;
• a controller for controlling the set of triacs to set the output voltage level at which the output current is for the time being supplied to the load, the controller controlling the triacs to set a high output voltage level so as to supply power at a set high power setting for a period of time THi starting upon the occurrence of a high power start condition and ending upon the occurrence of a high power end condition and to set a low output voltage level so as to supply power to the load at a set low power for a later period of time Tlo starting upon the occurrence of a low power start condition and ending upon the occurrence of a low power end condition;
• and
• a sensor of current supplied to the load,
• the controller during a transition period following time period THi and preceding time period TLo, controlling the set of triacs to set a series of output voltage levels diminishing controllably from the set high output voltage level to the set low output voltage level in a series of stepwise decreasing output voltage levels, each stepwise reduction of less than the specified percentage, and each stepwise reduction applied when the current supplied to the load has stabilized.