March 2019:

In future DRL will be concentrating on sales and support of the DVR2 regulators, generally suited to motorcycle use. We intend to continue sales and support of our well proven DVR3 and DVR4 products for six months or more, in order not to let down our customers with a bump.

Read more about the change in this post on our 'blog' site.

DVR3™ Regulator - Lucas style field

electronic dynamo regulator & cut-out: current limited, field to earth ('shunt')



Plus UK, European or Rest of World postage RoW includes Australasia, Americas, Africa & India!

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Current Limit
EARTH Polarity

Description and features of the DVR3™

The DVR3™ is a high output, current limited electronic dynamo regulator & cut-out unit to suit dynamos with one end of the field winding connected to the vehicle 'earth'. Such dynamos, including Lucas types, were fitted to many classic cars and other vehicles. (Sometimes known as 'shunt' field, although this terminology is not strictly correct.) Choice of Negative or Positive Earth versions. Maximum current outputs of 8, 11, 16 or 22 Amps (310 Watts) are available to suit 6 or 12 V systems. The field winding resistance of the dynamo must be greater than 2.5 ohms.

This is a modern electronic 'solid state' replacement for the original electromechanical two bobbin 'CVC' regulator units and 3 bobbin type with separate current regulation fitted in Classic Vehicles equipped with dynamo electrical generation. The DVR3 features improved performance over 'relay' types giving excellent charge voltage stability from the lowest revs to maximum speed, and zero low speed battery discharge into the dynamo. (Current limit accuracy is within approximately 5% of nominal current. E.g. a 22 Amp current limit unit will be limited to between 21 and 23 Amps.) The DVR3 is electrically and mechanically robust, housed in a strong aluminium housing for good heat transfer.

DVR3 size is 60 x 42 x 18 mm. The unit produces a very modest degree of heat but proper mounting is recommended to limit temperature rise for maximum service life. It is supplied with an adhesive thermal bonding pad on the top surface, for attaching to a flat (not hot) metal surface to act as a heat-sink. Alternatively a small finned heat-sink is available for the 22 Amp product to achieve enhanced cooling. A pair of vertical holes, with 54 mm centre spacing, M3 clearance (3.2 mm diameter) allow a pair of screws as an alternative (or additional) means to secure the regulator. Connections are by flying leads of approximately 130 mm. Bared wire ends allow the customer to connect using their preferred method.

Compare our 'DVR' regulators with other products on the market: they exhibit no battery discharge back to the dynamo at low revs. By employing MOSFET transistors in the cut-out function the DVR3 & 4 generate far lower heat output than other units using ordinary diodes to perform the cut-out. The battery charging voltage is always stable (above cut in speed) regardless of your speed. Furthermore your dynamo will start up (and be regulated) with no or very low battery charge.

View DVR3™ data sheet (Adobe Acrobat PDF format)

Read the experience of the owner of an immaculate Morris 8 from New Zealand who fitted a DVR3:

Morris 8 with DVR3 (Adobe Acrobat PDF format)


We also stock a small range of useful accessories to accompany a new Regulator.

View our range of Voltage Regulators