A portable generator assembly comprising an alternator installable in a vehicle, and a power converter. The alternator includes an AC output port electrically connected to the stator windings of the alternator for receiving the AC output signal, and providing access to the AC output signal such that the AC output signal can provide AC power at a location outside of the alternator's housing. The power converter is provided with a transformer, a frequency changer, and an electrical outlet. The transformer receives the AC output signal from the AC output port and increases the voltage of the AC output signal to at least about 120 V. The frequency changer receives the AC output signal having the increased voltage, and converts the frequency of the AC output signal to a frequency between about 45 to about 65 Hz. The electrical outlet receives the AC output signal having the increased voltage and converted frequency. An electrical implement, such as a hand drill, can be plugged into the electrical outlet so as to provide power for operating the electrical implement.

A configurable overload relay selectively operable in a single-phase mode of operation and a multi-phase mode of operation is configured to sense current flow through power conductors. The relay is further configured to determine a parameter related to the current flow, such as average current, vector sum of phase currents, and current imbalance, based on selection of either the single-phase or multi-phase mode of operation. Regardless of the selected mode of operation, the relay can provide protection for multiple types of power conductor fault conditions, including ground faults, overloads, and phase loss. The relay further can be configured to provide a reporting signal indicative of the value of the determined current-related parameter and/or the occurrence of the fault condition.

An automotive air conditioning system equipped with an electrical compressor uses a single-shaft, dual output generator to provide a low voltage output to drive existing 12-V or 24-V automotive electrical equipment and a high voltage output to drive the air conditioning motor-driven compressor, and a control device to control the electrical compressor.

A module for a bus rooftop air conditioner is self contained in that it has all the necessary components including a compressor, if desired, which when supplied with electrical power, can provide conditioned air to the passenger compartment of a bus. In addition, an electrically powered heater is provided in the air flowstream such that heated air can also be supplied to the passenger compartment when desired. Multiple units provide for incremental capacity requirements to be met as well as limp home capabilities.

In an inverter apparatus for air conditioner for converting DC voltage supplied from a DC power source into pseudo AC voltage of variable voltage and variable frequency by means of pulse-width modulation, a control circuit varies pulse-widths of the pseudo AC voltage in response to degree of rise/drop of the DC voltage from the nominal DC voltage; and when the voltage has an insufficient value to obtain the frequency-voltage characteristic, the control circuit controls switching devices to issue a maximum AC voltage obtained by the present DC voltage independent of frequency.