# Modified Sine Wave

## What is a Modified Sine Wave?

A modified sine wave is a version of a true sine wave that is characterized by a distinct ‘blocky’ appearance. It still is a sine wave as it is repetitive and oscillatory in nature, but rather than a smooth oscillation like a sideways letter ‘S’, it is more square in shape.

Key Takeaways:

• A modified sine wave is characterized by its distinctive blocky appearance.
• Modified sine wave systems are cheaper than pure sine wave, but are not compatible with all appliances.
• A pure sine wave is always needed for a grid tie system.

## Understanding Modified Sine Waves

A modified sine wave is a version of a true sine wave that is characterized by a distinct ‘blocky’ appearance. It still is a sine wave as it is repetitive and oscillatory in nature, but rather than a smooth oscillation like a sideways letter ‘S’, it is more square in shape.

A modified sine wave produces one instantaneous jolt of maximum voltage before then going to zero voltage for a moment and then to minimum voltage. The benefit to this type of current is that creating an inverter to handle the current is relatively inexpensive, but this also means that many appliances are not able to efficiently use the power converted by a modified sine wave inverter. For simple household needs, a MSW system offers decent efficiency at a lower cost.

For instance, many digital clocks and simple appliances run quite effectively on a modified sine wave current, while larger appliances such as refrigerator motors and fans will use up to 20% more power due to much of the modified sine wave current being at higher frequencies that they are not able to use.

One important reminder for anyone considering using a MSW system is that it is extremely easy to convert a true sine wave to a modified sine wave by clipping off certain parts, while the reverse is extremely difficult.

A pure sine wave is always needed for a grid tie system.

## Related Terms

Sine Wave – A sine wave is a geometric wave that moves up and down at a regular interval, and is defined by the function y = sin x.

Inverter – Or power inverter, is a device which converts direct current energy to alternating current energy so that it can be used by typical household appliances.

Micro-Inverter – A small inverter device that is attached to each photovoltaic panel to convert DC current to AC current.