High-voltage, electrical compressors

Published:  30 November, 2022

Design review
High-voltage (HV) electrical compressors have already been on the market for a while as they currently power most heating, ventilation and air conditioning (HVAC) systems in hybrid and electric vehicles. There are several advantages to the application of electrical compressors, and there are a couple of special features that differentiate them from a traditional belt-driven compressor.

HV electrical compressors are compact devices that circulate refrigerant efficiently in the AC or heat pump loop, powered by an electrical motor capable of high torque operation.

Automotive applications employ scroll-based technology where the refrigerant is compressed by rotation of a set of spirals. Compared to traditional belt-driven units, the design has fewer parts as there are no pistons, wobble plate mechanism or steering valves, in fact the only valve in the scroll system is a relatively simple metal valve to steer the refrigerant gas inlet and outlet within the compressor.

Many compressor models have two connectors located on the assembly. The larger socket is for the HV connection to the vehicle's battery and for safety reasons, both the socket and the wiring to the battery are bright orange, which indicates HV. The second, smaller socket is for the compressor communication with the HVAC system's control unit. The control unit sends input signals to the PIM, which translates them and directly runs the compressor via voltage signals that control the commanded level of electrical current sent to the electrical motor. The level of the electrical current steers the compressor's output torque and the frequency of the signal controls the speed of the motor.

Common failures

As with any other compressor, electric motor-driven AC compressors can equally suffer from malfunctions when exposed to system failures. Before blaming the compressor as the reason for the problem, a trained technician should always thoroughly inspect the system because most compressor breakdowns occur due to other root causes.

Electricity

Irregular compressor operation may be linked to erratic electrical signals to or within its electronics control module, for example. Other symptoms may indicate problems like poor system performance, unusual noise generation, or irregular operation, such as when the vehicle works only in some modes or does not activate at all.

Physical damage

The HV/AC compressor can easily suffer from physical damage, which may cause other severe system failures, for example, excessive friction in the inner parts and noise generation may indicate impaired compressor lubrication.

Lubrication

Similar to traditional compressors, lubricant is also critical for electric compressors. Besides lubricating the mechanical parts and cooling them down, the lubricant also insulates the electrical components.

WARNING! Some types of lubricant must never be used due to their moisture absorbing characteristics, for example. Incorrect oil application/mixing of oil will reduce its electrical insulation, causing a fault with the HV system. This may cause a dead short or may provoke system errors, which will then shut off the compressor or the vehicle itself.

Replacement

The company's range of thermal system components for new energy vehicles (NEV) consists of more than 720 items and caters for in excess of 2,900 OE part numbers. The programme now extends to pressure and temperature sensors and electric high-voltage AC compressors, which further supports the independent sector and provides it with access to the critical parts of the future, strengthening Nissens' NEV technical expertise in the process.

Remember, only qualified professionals with specialised training and certifications should replace an HV system and they must wear the appropriate personal protective equipment, follow safety rules and use HV tools, as well as other consumables designed for the vehicle. To learn more about new energy vehicle thermal systems, visit the Nissens Automotive expert knowledge portal at www.nissens.com/experts

Learn more

To learn more about new energy vehicle thermal systems, visit the Nissens Automotive expert knowledge portal at www.nissens.com/experts

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