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Speed controllers explained.

Why Use Speed Controllers & Limiters ?

In today’s ever growing markets there is a continual need to be able to control a motors speed for various applications.

Sometimes there is a need to limit, or ramp up and down an electric device to meet certain applications and uses, and that is where speed control comes into play.

This can be a daunting task to work out, as at times there is limited information available, to assist you work out what can be done and how.

Powerform controls offer a wide range of single phase speed controllers, limiters, vsd's and timers to suit every need. We are always more than happy to work with our clients to work out a solution for your speed controlling needs..

As a simple introduction below are  the speed control types available for single phase applications, from the powerform range.

Speed limiters –

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Ideally these are suited to be a set and forget low cost speed control / limiter option.

These are used to set a certain speed or limit, and then be left, usually for air balancing, commissioning purposes, reducing airflow, motor noise or when the required airflow or maximum required is not known, until the installation is complete.

Powerforms range of small footprint limiters ensures that all applications are catered for, right up to 20 amp motor / load applications.


Speed Controllers –



These are used for applications where a user adjustable speed or limit control option is required, so that a device can be speed controlled, or varied up or down as required.

All Powerform speed controllers offer the added feature of minimum speed / limit adjustment as standard. This is a major feature, as not all controllers on the market feature this important feature.

This allows a minimum speed or minimum limit for your application, to ensure the installation will always perform as you need it to, and avoid an installation to be controlled to run too slowly, or below its designed parameters by an end user, client or operator.

A lot of controllers in the market do not feature this, and the lack of this feature can lead to motors or applications running too slow, if the end user mistakenly dials the device to its very minimum.

In fan applications this can be critical, as this can lead to the fan motor stalling (drawing power but not turning, therefore there is no airflow to assist the motor to cool). This can cause the fan motor to overheat and cause it fail prematurely, sometimes within months of installation.

Powerform offer a diverse range of mounting & optional features, so that all possible application, installation and price considerations can be catered for.


VSD (variable speed drive) –

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Variable speed drives (VSDs) are a controller that regulates the speed and rotational force, or torque output of an electric motor.

VSDs are also called variable-frequency drives, adjustable-speed drives, variable-frequency inverters, or frequency converters.

VSD installations can increase energy efficiency (in some cases energy savings can be more than 50%), as they can change the speed of an electric motor by controlling the power that is fed into the machine.

The Powerform range of vsd’s feature dual control inputs as standard of 0 to 10 volt and 2 to 20 milliamps, and are easily switched from one input to the other by simply changing a jumper link internally. They also feature inbuilt EMI filters, auto off under 0.8v/1.5ma control signal, and minimum and maximum span & offset adjustment (min & max speed) ,ensuring they can meet every application and requirement.

They feature a small footprint, and are an easy to use, multifunction VSD.

All Powerforms drives are suitable for PSC motors, fans, blowers and pumps, or applications where the torque varies with speed. They can also provide effective electronic control of other types of resistive and inductive loads eg – lamps, transformers & heaters