taps will then be routed into the tap changer compartment through a terminal array. One possible design (flag type) of on load mechanical tap changer is shown to the right. It commences operation at tap position 2, with load supplied directly via the right hand connection. Diverter resistor A is short-circuited; diverter B is unused. In moving to tap 3, the following sequence occurs: Switch 3 closes, an off-load operation. Rotary switch turns, breaking one connection and supplying load current through diverter resistor A. Rotary switch continues to turn, connecting between contacts A and B. Load now supplied via diverter resistors A and B, winding turns bridged via A and B. Rotary switch continues to turn, breaking contact with diverter A. Load now supplied via diverter B alone, winding turns no longer bridged. Rotary switch continues to turn, shorting diverter B. Load now supplied directly via left hand connection. Diverter A is unused. Switch 2 opens, an off-load operation. The sequence is then carried out in reverse to return to tap position 2. Solid-state tap changer This is a relatively recent development which uses thyristors both to switch the transformer winding taps and to pass the load current in the steady state. The disadvantage is that all non-conducting thyristors connected to the unselected taps still dissipate power due to their leakage currents and they have limited short circuit tolerance. This power consumption can add up to a few kilowatts which appears as heat and causes a reduction in overall efficiency of the transformer; however, it results in a more compact design that reduces the size and weight of the tap changer device. Solid state tap changers are typically employed only on smaller power transformers. Voltage considerations If only one tap changer is required, manually operated tap points are usually made on the high voltage (primary) or lower current winding of the transformer to minimize the current handling requirements of the contacts. However, a transformer may include a tap changer on each winding if there are advantages to do so. For example, in power distribution networks, a large step-down transformer may have an off-load tap changer on the primary winding and an on load automatic tap changer on the secondary winding or windings. The high voltage tap is set to match long term system profile on the high voltage network (typically supply voltage averages) and is rarely changed. The low voltage