The purpose of the liquid coolant is to carry away heat developed by the transformer. Chemicals may be added to the coolant to protect against algae, corrosion or mineral deposits. The resultant solution must be compatible with plumbing components and must not inhibit the ability of the liquid coolant to transfer heat. Just as when adding antifreeze solutions to an automobile engine, it is best to minimize the amount of antifreeze in a transformer's coolant due to the poor heat transfer nature of antifreeze. RWMA Bulletin 14 provides guidelines for liquid coolant makeup.

ANSI/AWS Bulletin Z49.1 states that the secondary of a transformer shall be grounded by one of two methods or in the case of non-portable machines use an isolation contactor. The two methods listed in Z49.1 are; 1) Permanent ground on the welding secondary circuit. 2) Ground reactor. The choice of using a permanent ground or a ground reactor is an issue of the weld process and the machine design. If multiple transformers make contact to a common point a ground reactor can prevent secondary circulating currents. There are many other conditions that a ground reactor can eliminate circulating currents and should be evaluated in the machine design. Both methods meet the requirements of Z49.1 and both methods are safe, the choice of which method to use is a machine design or welding process issue.

The transformer turns ratio is very accurate; it is controlled by the transformer manufacture and is tested several times in the quality control process of manufacturing transformers. Often the turns ratio is used in a weld control to calculate the secondary current when the control is monitoring the primary current. It is common practice to adjust the turns ratio in the weld control to get the weld control and some external current meter to coincide, using the turns ratio for this purpose has nothing to do with the transformer, and is really a issue of calibrating the weld control. The true turns ratio is the ratio of turns of wire on a primary coil to the number of turns on a secondary coil. This ratio is a physical quantity and can only be changed by selecting a different turn on the primary coil through a tap switch or some other hard wired connection.

All three terms refer to the same thing and may be used interchangeably. Today's preferred term is Inverter DC. Inverter DC transformers operate at a frequency greater than 60 Hz (usually 1000 or 1200 Hz) and have diodes on the output side of the transformer.

The common misconception is that resistance welding transformers are current sources. They are not. They are voltage sources. A transformer's KVA rating is a thermal rating and deals with how many welds per minute it can make and not the weld current that it can produce. A higher KVA rating does not necessarily mean more welding current.